An analysis of current knowledge and a complete practical guide.

Transcription

1 10777 LMA Brimacombe Cov copy Page 1 An analysis of current knowledge and a complete practical guide. Sponsored by: Author: Professor Joe Brimacombe Department of Anaesthesia and Intensive Care James Cook University, Cairns Base Hospital, Cairns 4870, Queensland, Australia

2 10777 LMA Brimacombe Cov copy Page 2 First published in 2004 by The Laryngeal Mask Company Limited Published in 2007 by The Laryngeal Mask Company Limited Copyright The Laryngeal Mask Company Limited, 2004 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electrical, mechanical, photocopying, recording or otherwise, without the prior permission of the publisher. LMA, LMA Classic, LMA CTrach, LMA Fastrach, LMA Flexible, LMA ProSeal, LMA Supreme, LMA Unique, The Laryngeal Mask Company Limited logo and its component parts are trade marks of The Laryngeal Mask Company Limited, PO Box 221, Le Rocher, Mahé, Seychelles. LT and LTS are registered trade marks of the VBM Medizintechnik GmbH, Einsteinstr. 1, D Sulz a.n, Germany. SLIPA is a trade mark of SLIPAmed UK, Minories, London, UK. The opinions in this publication are those of the author and may not reflect the Laryngeal Mask Company Limited s indications or instructions for these devices.

3 LMA Analysis q Page 1 Contents Page I. INTRODUCTION 3 II. HISTORY 3 III. EQUIPMENT 5 A. DEVICE DESCRIPTION 5 B. ACCESSORY EQUIPMENT, LASER AND MAGNETIC RESONANCE IMAGING 8 C. GAS PERMEABILITY 8 D. ELASTIC PROPERTIES OF THE CUFF 8 E. CLEANING AND STERILISATION 8 IV. ANATOMY 9 A. AIRWAY TUBE 9 B. DRAIN TUBE 9 C. MECHANICAL CORD CLOSURE 10 D. DYNAMIC ANATOMIC CHANGES 10 V. PATHOPHYSIOLOGY 10 A. CARDIOVASCULAR SYSTEM Descriptive studies Comparative studies 11 B. RESPIRATORY SYSTEM Airway obstruction Gas exchange Work of breathing, leak fraction and dead space Airway protective reflexes Hiccup Pulmonary defenses, laryngeal function and pulmonary pathology 12 C. GASTROINTESTINAL SYSTEM Oesophageal function Regurgitation and gastrointestinal reflexes 12 D. OTHER SYSTEMS 13 E. PHYSIOLOGICAL INFORMATION Cardiac output Gastric volume/ph Core temperature, oximetry, pressure and ph Respiratory monitoring 13 VI. FUNCTION 13 A. SEAL WITH THE RESPIRATORY TRACT Mechanism of seal and relationship to cuff volume Seal for gas exchange Seal for prevention of soiling from above the cuff 14 B. SEAL WITH THE GASTROINTESTINAL TRACT Mechanism of seal Efficacy of seal Gastric insufflation and distention 16 C. CONDUIT TO THE RESPIRATORY TRACT 16 D. CONDUIT TO THE GASTROINTESTINAL TRACT 16 VII. PRE-ANAESTHESIA PHASE 16 A. PRE-USE CHECK TESTS 17 B. INDICATIONS AND CONTRAINDICATIONS 17 C. SIZE SELECTION 17 VIII. PLACEMENT PHASE 17 A. CO-INDUCTION / INDUCTION AGENTS AND DEPTH OF ANAESTHESIA 18 B. INSERTION THEORY 18 C. INSERTION TECHNIQUES Digital Introducer tool Laryngoscope-guided, GEB-guided 20 D. INSERTION SUCCESS RATES 21 E. CUFF INFLATION AND FIXATION 22 F. MALPOSITION Distal cuff in laryngopharynx or glottic inlet Distal cuff folded over 23 3.Severe epiglottic downfolding Glottic compression Anterior flexion 24 G. DRAIN TUBE Air leaks Patency 25 H. GASTRIC TUBE INSERTION When to insert How to insert 26 IX. MAINTENANCE PHASE 27 X. EMERGENCE PHASE 27 XI. RESUSCITATION 28 XII. INTENSIVE CARE 28 XIII. DIFFICULT AIRWAY 29 XIV. PAEDIATRICS 29 XV. COEXISTING DISEASES 29 XVI. SURGERY 30 XVII. PROBLEMS 32 A. AIRWAY MORBIDITY AND TRAUMA 32 B. DEVICE-RELATED PROBLEM 33 C. MANAGEMENT OF REGURGITATION 33 D. MANAGEMENT OF ASPIRATION 33 XVIII. LMA PROSEAL VERSUS OTHER NON-LMA DEVICES 33 A. LARYNGEAL TUBE AIRWAY Fibreoptic position Mucosal pressure Spontaneous breathing Positive pressure ventilation 34 B. LARYNGEAL TUBE SUCTION 34 C. STREAMLINED PHARYNGEAL AIRWAY LINER 34 D. MULTIPLE DEVICES 34 E. LARYNGOSCOPE-GUIDED TRACHEAL INTUBATION Haemodynamic responses, airway reflexes and sore throat Gynaecological laparoscopy Laparoscopic cholecystectomy 35 XIX. SUMMARY 35 XX. REFERENCES 36 XXI. TABLES 57 1

4 LMA Analysis q Page 2 Contents of Tables Table List of commonly used abbreviations OLP = oropharyngeal leak pressure PPV = positive pressure ventilation IT = introducer tool DT = drain tube GT = gastric tube FM = face mask TT = tracheal tube LG-TI = laryngoscope-guided tracheal intubation GEB = gum elastic bougie LT = laryngeal tube LTS = laryngeal tube suction PLMA = ProSeal laryngeal mask airway ICU = intensive care unit SLIPA = streamlined liner of the pharyngeal airway 2 Page Table 1. Differences between the 1995 Prototype and the LMA ProSeal 57 Table 2. Modified features of the LMA ProSeal compared with the LMA Classic 58 Table 3. LMA ProSeal specifications 59 Table 4. Summary of magnetic resonance imaging artefact information for the LMA ProSeal 60 Table 5. Oropharyngeal leak pressure (OLP), in vivo and in vitro intracuff pressures and directly measured pharyngeal mucosal pressures at various locations with increasing cuff volume for the classic laryngeal mask airway (LMA Classic ) and ProSeal laryngeal mask airway (LMA Proseal ) 18. Data are mean (95% CI). 61 Table 6. Studies comparing the fibreoptic position of the bowl from the distal aperture of the airway tube for the LMA Classic and LMA ProSeal 62 Table 7. Studies determining the fibreoptic position of the distal cuff from the distal aperture of the drain tube 63 Table 8. Composite data for directly measured mucosal pressures in the anterior (base of tongue), lateral and posterior pharynx for six extraglottic airway devices at an oropharyngeal leak pressure of 30 cm H2O or at maximum seal 18, Data are mean±sd or mean (95% CI). Units are cm H2O. 64 Table 9. Studies determining oropharyngeal leak pressure (OLP) for the LMA ProSeal and LMA Classic. Data are mean±sd or (95% CI) or [range]. 65 Table 10. Change in the oropharyngeal leak pressure in different head and neck positions for the LMA Classic and LMA ProSeal 23. Data are % change from neutral position with the intracuff pressure set at 60 cm H2O. 66 Table 11. The oesophageal pressures at which fluid first appears in the bowl (intracuff), above the cuff (supracuff) and in the drain tube (LMA ProSeal only with drain tube unclamped) for the LMA Classic, the LMA ProSeal with the drain tube clamped (LMA ProSeal -clamped) and the LMA ProSeal with the drain tube unclamped (LMA ProSeal -unclamped) by cuff volume in cadavers 71. Data are mean (95% CI) unless otherwise stated. Units are cm H2O. 66 Table 12. Situations where a better seal, airway protection and access to the gastrointestinal tract are desirable 67 Table 13. First-time and overall insertion success rates for the LMA ProSeal 68 Table 14. Diagnostic signs for correct position and the five main malpositions of the LMA ProSeal 69

5 LMA Analysis q Page 3 I. Introduction The LMA ProSeal, first described by Brain and colleagues in , is the most ingenious and versatile of the LMA devices, and has the greatest potential to improve patient safety. It supercedes the LMA Classic and disposable LMA (LMA Unique ) in most clinical situations, and challenges the tracheal tube (TT) in many clinical situations. Brain s design goal was to construct a laryngeal mask with improved ventilatory characteristics that also: (i) offered protection against regurgitation and gastric insufflation; (ii) provided information about whether it was malpositioned; and (iii) could be inserted without digital intraoral manipulation. The principle new features are a modified cuff and a drain tube (DT). Conceptually, the LMA ProSeal can be regarded as a double mask forming two end-to-end junctions, one sealing around and opening into the entrance to the respiratory tract, the other sealing around and opening into the entrance to the gastrointestinal tract. The key conceptual difference from the LMA Classic is that the second mask opens into the gastrointestinal tract. There are currently more than 110 publications on the LMA ProSeal, including 40 papers and 33 case reports. In this review article, which is partly based on a chapter in a new book by the author entitled Laryngeal Mask Anaesthesia Principles and Practice, these publications will be analysed and practical guidelines provided. Topics of particular interest include: (i) tests for malposition; (ii) guided techniques for insertion, notably the use of the gum elastic bougie (GEB); and (iii) the role of the LMA ProSeal in difficult airway management. The main topic of controversy is its safety in patients at risk of aspiration. Full abstracts or summaries of most LMA ProSeal publications are provided in the reference section. II. History The LMA Classic was a compromise between ease of insertion, simplicity of design and efficacy of seal, and was never regarded by Brain as the best form of the device 2. It was always clear that it had two fundamental limitations: the efficacy of seal was sometimes inadequate for positive pressure ventilation (PPV), and it did not protect against regurgitated gastric contents. At the end of an account of the early development of the LMA, published in 1991 in the European Journal of Anaesthesiology, Brain publicly challenged himself to developing a better LMA by stating that he: would continue to search for the ultimate laryngeal mask which would protect the patient from aspiration of gastric contents. Several interesting designs have been developed and are currently being evaluated. The story of the laryngeal mask is far from over. Brain realised that a more effective seal could be attained by one of three methods: (i) increasing the force with which the mask is pressed into the periglottic tissues; (ii) increasing the surface area over which this force is applied; or, (iii) choosing a different site within the pharynx to form a seal. Brain also realised that the LMA could incorporate some form of drain device either a tube or a groove - to divert regurgitated fluid away from the respiratory tract and to prevent gastric insufflation. A variety of prototypes were tested which proved the feasibility of these concepts, but none were developed because they were complex, bulky, positionally unstable and difficult to insert (Figure 1, 2). Another important realisation was that if the DT was located at the distal end at the cuff, an effective airtight seal could only be obtained if the distal cuff was correctly positioned in the hypopharynx. An advantage of this configuration was that malposition could be diagnosed with a high degree of certainty, something not easily done with the LMA Classic, even with a fibreoptic scope. Fig 1. Lateral view of LMA ProSeal prototypes with various drain tube arrangements. The central prototype has the drain tube attached to the dorsal surface of the airway tube. Photo courtesy of Archie Brain. 3

6 LMA Analysis q Page 4 Fig 2. Prototype LMA ProSeal (1995) [see Table 1]. DT=drain tube. BB=bite block. DC=dorsal cuff. VC=ventral cuff. Between 1983 and 1994, a number of different prototypes were constructed and tested. One of these prototypes was described in a paper published in (Figure 2). This design incorporated a second mask to isolate the upper oesophagus and a second dorsal cuff to increase the seal against the glottis. The second tube was located behind the airway tube and ran posterior to the cuff. A within-patient comparison of seal pressures in 20 adult patients showed that oropharyngeal leak pressure (OLP) was significantly higher for this prototype than the LMA Classic, and equalled or exceeded 50cm H2O in all patients. This prototype also provided functional isolation of the respiratory tract from the gastro-intestinal tract, as judged by a lack of air leak and placement of a gastric tube (GT) via the DT. However, along with its predecessors, this prototype was stiff and bulky. Variations of this 1995 prototype were tested and/or used in clinical practice by researchers in Australia 4, Italy 5,6 and Spain 7. This experience yielded three reports where regurgitation occurred without aspiration 4,6,7, and evidence that the design concept was also viable in children 7. Meanwhile, other inventors were trying to improve on the LMA Classic design in terms of airway protection 8 and efficacy of seal 9. The first challenge came in January 1994 from TM Akhtar 8, an anaesthetist working in Dumfries, Scotland, who had developed a home-made LMA that he claimed protected against regurgitation. The rather wordy oesophageal vent-laryngeal mask airway was an LMA Classic with a cuffed TT fused posteriorly and protruding from the distal end. The cuffed TT penetrated into the upper oesophagus to vent regurgitated stomach contents away from the trachea in much the same way as the oesophageal obturator airway. This paper triggered no less than four letters of criticism. Brain 10 noted that he had investigated a similar device almost a decade before, but discarded it since placement was complex and traumatic. He also believed that penetrating the upper oesophageal sphincter was as likely to provoke regurgitation as prevent it. These objections were reiterated by Asai 11, Sorooshian 12 and Gajraj et al 13 in a series of letters published later that year. Akhtar 14, in his defence, emphasised that the presence of the LMA anteriorly forces the TT along the posterior pharyngeal wall making impaction with the glottis unlikely. Brain 10 pointed out that placement of a TT in the oesophagus is best conducted once the LMA is placed since it can act as a shield protecting the glottis from trauma. A second and much more serious challenge came in May 1998 from a large medical company, Augustine Medical Inc, who claimed to have developed a laryngeal mask with a better seal. The so-called glottic aperture seal airway consisted of a curved tubular component that ends in the middle of an elliptical foam cushion glottic component 9. By chance, an LMA company representative heard a lecture about the device at the American Society of Anaesthetists Annual General Meeting and took legal advice as it appeared to be an LMA in all but name. A letter was sent to Augustin Medical asking them to desist and the next thing Dr. Brain knew was that Augustin Medical countered by demanding that the Laryngeal Mask Company Limited prove that the glottic aperture seal airway was infringing the LMA patent. Dr. Brain was obliged to submit to a lengthy cross-examination by their lawyers in New York, who pressed him very hard on the exact meaning of the language of original patent, which they implied might be invalid. They even went so far as to interview him a second time in the UK, where they demanded to see the contents of the museum of LMA airways at the Royal Berkshire Hospital in Reading. However, they were ultimately unsuccessful in trying to claim that the patent was invalid. With the development of the intubating LMA, the LMA Fastrach, completed, and increasing inventive competition, Dr. Brain concentrated on improving the 1995 prototype. A wide number of designs were tested with the help of Chandy Verghese in the Royal Berkshire Hospital. Some were given names such as the double cuff LMA, the gastro LMA (Mark I and II), high-seal LMA and, simply, LMA II, but none were considered sufficiently better than the LMA Classic to warrant manufacture (Figures 3-6). 4

7 LMA Analysis q Page 5 Fig 3. Double cuff LMA (1994). Photo courtesy of Archie Brain. Fig 4. Gastro LMA Mark I (1994). The inflated balloon pushes the ventral cuff into the periglottic tissues to increase the seal. The drain tube is dorsal to the airway tube. Photo courtesy of Archie Brain. Fig 5. Gastro LMA Mark II (1996). The balloon has been replaced by a less protruberant dorsal cuff and the drain tube is now parallel with the airway tube. Photo courtesy of Archie Brain. Fig 6. LMA II (1997). This was intended as a successor to the LMA Classic. Note the smaller drain tube and the anteriorly sloping distal aperture, both features ultimately incorporated into the LMA ProSeal. Photo courtesy of Archie Brain. Fortunately, a series of major design breakthroughs occurred in 1998 and 1999 that resulted in a prototype LMA ProSeal being produced for the purposes of clinical testing in June These design breakthroughs are listed in Table 1. The most important of these were: (i) a change in shape of the proximal end of the cuff; (ii) the attachment of the DT alongside, rather than behind, the airway tube; (iii) incorporation of the distal DT within the bowl; (iv) anatomic shaping of the DT s distal orifice; and (v) the addition of an introducer tool (IT). Early clinical testing was conducted in the UK, by Verghese and colleagues; in Italy, by Agro and colleagues; in Spain, by Navia, Garcia de Lucas and colleagues; in Germany, by Fullekrug and colleagues; in Austria, by Keller and colleagues; in France, by Capdevilla and colleagues; in the USA, by Rosenblatt and Dierdorf; and in Australia by the author and colleagues. The feedback from these trials was positive and fullscale manufacture of the LMA ProSeal began in early The first country where the LMA ProSeal was made available was Australia, in June III. Equipment A. Device description The LMA ProSeal is made from medical grade silicone and is reusable (Figures 7-12). The different or modified features compared with the LMA Classic are listed in Table 2 and illustrated in Figure 13. In addition, the LMA ProSeal lacks mask aperture bars, as the DT functions as a solitary mask aperture bar for the accessory vent, and the deeper bowl makes epiglottic occlusion of the distal aperture less likely. The mask and inflation line are identical to the LMA Classic. A plug has recently been added to the pilot balloon (LMA ProSeal Red Plug) which vents the cuff during autoclaving to prevent damage from residual air and/or fluid (Figure 14). The plug is pulled out prior to autoclaving and re-inserted for clinical use. The LMA ProSeal is currently available in sizes 1.5, 2, 2.5, 3, 4 and 5. The adult cuff has identical proportions, but different dimensions among sizes. The paediatric sizes are not scaled down versions of the adult sizes, as they lack a dorsal cuff and have a relatively large DT (Figure 15). There is only one study describing its use in children 15 [see section XIV. Paediatrics]. 5

8 LMA Analysis q Page 6 The IT is a reusable clip-on/clip-off device that comprises a thin, curved, malleable, metal blade with a guiding handle similar to the intubating LMA Fastrach. Its inner surface and curved tip are coated with a thin layer of transparent silicone, which also protrudes beyond the distal end, to reduce the risk of trauma if it slipped through the insertion strap. The distal end fits into the insertion strap and the proximal end clips into the airway tube above the bite block with the proximal DT resting to one side. The LMA ProSeal device specifications are listed in Table 3. Fig 9A-D. Insertion strap (A) and distal portion of the introducer tool. (B). The finger (C) and introducer tool (D) easily fit underneath the strap. The silicone outer surface of the introducer tool protrudes slightly beyond its distal end to prevent trauma if it slipped anteriorly (arrow). Fig 7. Components of the LMA ProSeal. Fig 10. Oblique view of the bite block. Fig 8A-E. A. View of ventral cuff. B. View of proximal bowl. C. Closer view of drain tube and distal aperture in the proximal bowl. D,E. Side views of distal cuff, inflated and deflated. The distal aperture of the drain tube is sloped at 45 to facilitate flattening of the distal cuff for insertion (D,E). The support ring is seen through the deflated distal cuff (arrow). DA=distal aperture. AV=accessory vent. DT=drain tube. 6

9 LMA Analysis q Page 7 Fig 11. The LMA ProSeal with the introducer tool attached. Inset shows the proximal airway tube clipped into the proximal matching slot with the proximal drain tube free to the side. Fig13 A-C. Ventral (A), dorsal (B) and lateral (C) views of the LMA ProSeal (left or lower) and LMA Classic (right or upper). The LMA ProSeal cuff is wider proximally, has a more protruberant distal section and the airway tube is not pre-curved. Fig 12. The LMA ProSeal has similar anteroposterior flexibility to the LMA Flexible, but less lateral flexibility. Fig 14. The LMA ProSeal Red Plug. When open, this vents the cuff during autoclaving to prevent damage from residual air and/or fluid. 7

10 LMA Analysis q Page 8 Fig 15. The size 1.5, 2 and 2.5 LMA ProSeal. Fig 16. Hypopharynx (H) seen from below in a cadaver specimen after neck dissection. A. Before insertion. B. After insertion of LMA Classic. Note that the hypopharyngeal sac is collapsed before insertion (white arrow) and bulges after insertion (black arrow). Photo courtesy of Archie Brain. B. Accessory equipment, laser and magnetic resonance imaging In addition to the IT, there are two categories of accessory equipment used with the LMA ProSeal : (i) instruments that are inserted into the gastrointestinal tract; and (ii) items that help detect malposition by providing a visual signal of pressure changes in the DT. The former includes: (i) the GT; (ii) GEB; (iii) temperature probe; (iv) trans-oesophageal echocardiograph; (v) manometer; (vi) fibreoptic scope; (vii) oximetry probe; (viii) oesophageal stethoscope; and (ix) gastric balloon tube. Items that help detect malposition include: (i) a soap bubble ring applicator; (ii) thread; and (iii) a waterbased lubricant. The water-based lubricant should be contained in a tube rather than a sachet, as it is easier to inject into the DT. There are no publications about the thermal resistance of the LMA ProSeal to laser strike, but it is likely that it will be similar to the LMA Classic and LMA Flexible. The LMA ProSeal contains metal wires and exhibits magnetic field interactions during magnetic resonance imaging, which are given in Table 4. C. Gas permeability There is one anecdotal report. Nicholls and Patel 16,in 2001, described the intracuff pressure changes in a 40- yr-old male undergoing a 5 hour mastoid procedure using 57-63% N2O. Intracuff pressure increased from 60cm H2O at time zero to approximately 100cm H2O after 1 hour and 115cm H2O after 2 hours, and remained stable thereafter. This is a similar pattern to the LMA Classic suggesting similar permeability 17. D. Elastic properties of the cuff There is one study. Keller and Brimacombe 18, in 2000, found that in vitro and in vivo elasticity was lower for the LMA ProSeal than the LMA Classic (Table 5). This probably reflects the larger cuff size. E. Cleaning and sterilisation The guidelines for cleaning and sterilisation are identical to the LMA Classic. However, the LMA ProSeal is a more complex shape and requires more attention. In particular, the finger strap and accessory vent form pockets where secretions can accumulate and both must be exposed and cleaned. A smaller pipe cleaner should be used to clean the DT than the airway tube. Deflation of the cuff is more difficult as residual air can accumulate in the dorsal cuff. The deflation tool will facilitate correct deflation. A dedicated cleaning brush has been designed specifically for the LMA ProSeal. Opening the LMA ProSeal Red Plug will prevent high intracuff pressures during autoclaving in the event of incomplete evacuation. 8

11 LMA Analysis q Page 9 IV. Anatomy The anatomic position occupied by the LMA ProSeal is similar to, but more extensive than, the LMA Classic. The larger, conical, anatomic-shaped distal cuff fills the hypopharynx A more completely, and the larger, wedge-shaped proximal cuff fills the proximal laryngopharynx more completely, both to form a better seal with their respective tracts. In principle, when compared to the LMA Classic : (i) the anteroposterior diameter of the pharynx should be increased due to the deeper bowl and dorsal cuff; (ii) epiglottic downfolding should be more frequent due the impaction with the larger cuff; and (iii) glottic distortion should be more common due to the glottic inlet being compressed anteriorly by the larger distal cuff and compressed inwards by the larger ventral cuff. There are no radiological reports, but there are 15 fibreoptic reports determining the position of the bowl (from the airway tube) and the distal cuff (from the DT): three case reports and 12 studies 1, 18, The normal fibreoptic views from the airway and DT are shown in Figure 17. Fig 17. Normal fibreoptic position of the LMA ProSeal. A. View from airway tube with the epiglottis unseen. B. View from airway tube with the epiglottis seen. C. View through the drain tube showing complete closure of the distal aperture by the hypopharyngeal/oesophageal mucosa. tub=epiglottic tubercle. Photos courtesy of Michael Stix and Cornelius O Connor Jr. A The hypopharynx is the pocket-shaped termination of the pharynx. It is located behind and beneath the arytenoid and cricoid cartilages. It is approximately 3.5 cm long and extends from the upper level of the arytenoid cartilages superiorly to the upper oesophageal sphincter inferiorly. It is bounded anteriorly by the mucous membrane covering the arytenoid cartilages (upper 3/7) and anteroinferiorly by the mucous membrane covering the lamina of the cricoid cartilage (lower 4/7), laterally by the lower portion of the pyriform fossae, posteriorly by the seam of the inferior constrictor, inferiorly it tapers into the upper oesophageal sphincter. It is the key anatomic structure to understanding the LMA ProSeal (Figure 15). A. Airway tube There are seven studies comparing the fibreoptic position of the bowl from the airway tube of the LMA ProSeal and LMA Classic (Table 6). Meta-analysis of these data reveals that vocal cord visibility is similar, but epiglottic visibility is more common with the LMA ProSeal (50% vs 35%, p< ). This does not appear to impede ventilation 25,27, perhaps because of the accessory vent. These studies also show that: 1. fibreoptic position is similar for digital and IT-guided insertion fibreoptic position is unchanged by head and neck positional adjustments 23 or cuff inflation 23,24,27 3. the frequency of oesophageal visibility from the airway tube is low for both the LMA ProSeal and LMA Classic fibreoptic position is probably similar for obese and normal weight patients 26 (interstudy comparison) 5. slight malrotation is more common with the LMA ProSeal than the LMA Classic (15% vs 0%) 23 - this may be related to residual rotation in the sagittal plane, or the larger cuff causing glottic distortion 6. the glottis is more frequently visible with the LMA ProSeal than the VBM Laryngeal Tube airway (LT ) the distal cuff usually sits posterior and caudal to the interarytenoid muscle epiglottic downfolding occurs in 5% the fibreoptic position of the glottis correlates with ease of GT insertion the foldover malposition occurs in 10% anatomic position plays a major role in determining resistance to gas flow the LMA ProSeal induces anterior laryngeal structural movement and rotation of the arytenoids relative to the cricoid cartilage 34 B. Drain tube The DT provides a unique opportunity to obtain information about the anatomic location of the distal cuff, and sometimes whether the upper oesophageal sphincter is open or closed. The following views may be seen from the DT: (i) mucosa blocking the end of the DT, which suggests that the distal cuff is sitting in the distal hypopharynx; (ii) a short conical tube of mucosa, which suggests that the distal cuff is sitting in the proximal hypopharynx; (iii) the oesophageal lumen, which shows that the distal cuff is sitting in the hypopharynx and the upper oesophageal sphincter is open; and (iv) glottis, epiglottis or arytenoids, which shows the distal cuff is 9

12 LMA Analysis q Page 10 sitting in the laryngopharynx. In addition, the fibreoptic scope can identify DT compression suggesting the distal cuff is folded over. There are five studies providing information (Table 7). These show that the distal cuff is in the hypopharynx in 96% [420/436] and the upper oesophageal sphincter is open in 2-9%. Upper oesophageal sphincter opening may be related to reflex relaxation, or a direct mechanical effect. There is tentative evidence that the distal tip moves slightly proximally in 4-7% when the cuff is inflated 24. The position of the DT does not change in different head and neck positions 23, and is similar for digital and IT-guided insertion 24. C. Mechanical cord closure Mechanical cord closure is an uncommon, but important anatomic phenomenon causing airway obstruction in approximately 0.3% (19/6321) of patients with the LMA ProSeal 36. It is probably caused by the distal cuff compressing the glottic inlet anteriorly and/or inward rotation of the arytenoids due to a reduction in the tension of the vocal cords 20. Withdrawal of air from the cuff, and/or moving the head and neck into the sniffing position, and/or applying jaw thrust may resolve this problem by reducing the compressive force. Mechanical cord closure has been reported with the LMA Classic in association with cricoid pressure and a similar mechanism proposed 37. Compressive forces can also cause airway obstruction at the level of the aryepiglottic folds and/or by infolding of the cuff. The relative contribution of these three locations vocal cords, aryepiglottic folds and cuff infolding to mechanical airway obstruction with the LMA ProSeal is unknown. D. Dynamic anatomic changes Stix et al have published two case reports providing important information about the dynamic anatomic changes. The first describes oesophageal insufflation during PPV 22. This was due to the larynx being displaced anteriorly and the pyriform fossae being exposing laterally during maximum sustained airway pressure. The mucosa overlying the DT tip was seen peeling away as the oesophageal lumen opened during insufflation. The second describes gastric distention due to oesophageal aspiration of air in a spontaneously breathing patient with partial airway obstruction 21. Fibreoptic observation down the airway tube revealed a narrow glottis that collapsed during inspiration. There was abnormal inward rotation of the arytenoid vocal processes, causing them to contact each other in the midline. During inspiration 10 the vocal cords were drawn together. Fiberoptic observation down the DT revealed an oesophageal lumen that opened during inspiration. V. Pathophysiology In principle, pathophysiological responses for the LMA ProSeal should be generally similar to the LMA Classic. However, a difference in: (i) cardiovascular physiology might arise from reduced mucosal pressures (reduced mucosal ischaemia) and increased difficulty with insertion (increased haemodynamic stress response); (ii) respiratory physiology might arise from the narrower airway tube (increased work of breathing and lower dead space) and more frequent epiglottic downfolding (increased work of breathing); and (iii) gastrointestinal physiology might arise from the larger cuff (influencing pharyngo-oesophageal reflexes) and the DT (exposing the upper oesophageal sphincter to atmosphere). However, few studies address these issues. A. Cardiovascular system The influence of the LMA ProSeal on pharyngeal perfusion has not been measured directly, but mucosal pressures 38 are usually: (i) lower than pharyngeal perfusion pressure; (ii) similar to the LMA Classic 18 (Table 5); and (iii) lower than the LT, cuffed oropharyngeal airway, LMA Fastrach, oesophageal tracheal combitube (Table 8). There is no published data about the influence of the LMA ProSeal on the carotid artery or internal jugular vein, but the larger cuff may cause more distortion/compression than the LMA Classic. There are 7 studies providing information about the systemic cardiovascular responses 24,25,27,39-42, but in only 3 are these responses a primary variable There are 2 descriptive studies 40,41 and 1 study comparing it with laryngoscope-guided tracheal intubation (LG-TI) Descriptive studies Howarth et al 40, in a 2002 study of 100 adults, detected no changes in heart rate or blood pressure during laryngoscope-guided, GEB-guided insertion. Evans et al 41, in a 2002 descriptive study of 300 adults who were either paralysed or breathing spontaneously, found that there were no cardiovascular responses to insertion, with a small reduction in heart rate 5 minutes after insertion and significant decreases in mean arterial pressure at 1 and 5 minutes after insertion.

13 LMA Analysis q Page Comparative studies A study reported that haemodynamic responses are lower for the LMA ProSeal than LG-TI 42 [see XVIII, E]. The other studies hint that cardiovascular responses are similar to the LMA Classic 25 and the LT 39, and are uninfluenced by cuff volume or tidal volume 27. B. Respiratory system 1. Airway obstruction The incidence of airway obstruction is similarly low for the LMA ProSeal and LMA Classic [Meta-analysis using Fisher s method: c>24, p< ,24,25,27 ]. For example, Brimacombe and Keller 24 reported no episodes of airway obstruction with either device from 120 paralysed patients, and Brimacombe et al 25 reported airway obstruction in only 1.6% for the LMA ProSeal and 0.5% for the LMA Classic from 384 nonparalysed patients. However, airway obstruction may be more likely immediately after insertion 26,47. Keller et al 26 found that airway obstruction may have contributed to initial failed insertion in up to 10% (6/60) of nonparalysed patients using the LMA ProSeal. The incidence of mechanical airway obstruction with the LMA ProSeal is approximately 0.3% 36. There are 2 studies comparing airway obstruction versus the LT. Brimacombe et al 39, in a 2002 study of 120 anaesthetised, paralysed adults, found that the incidence of airway obstruction was lower for the LMA ProSeal (2% vs 17%); however, Gaitini et al 48, in a 2002 study of 100 anaesthetised, paralysed adults, found that the incidence was similar. The incidence of stridor is unknown, but there have been 2 anecdotal reports, both of these were associated with oesophageal aspiration of air 21, Gas exchange The incidence of hypoxia and hypercarbia are similar for the LMA Classic and LMA ProSeal [Meta-analysis using Fisher s method: c> 18 25,27,50 ]. For example, Brimacombe et al 25, in a 2002 study of 384 nonparalysed adults, found that the incidence of hypoxia (SpO2 <90%) was 2.1% for the LMA Classic and 1.6% for the LMA ProSeal and that SpO2 and endtidal CO2 (ETCO2) were identical. However, in situations where high airway pressure ventilation is required, gas exchange may be less effective with the LMA Classic due to increased leak fraction. There are 3 studies looking at high airway pressure ventilation 26,27,50 and 3 comparing gas exchange with other airway devices: one with the LT 39, one with the LTS 48 and one with the TT High airway pressure ventilation. Brimacombe et al 27, in a 2001 crossover study of 30 anaesthetised paralysed females, found that the LMA ProSeal and LMA Classic are equally effective ventilatory devices at tidal volumes of 8 and 12 ml/kg. Maltby et al 50, in a 2002 study of 209 women for gynaecological laparoscopy, found that SpO2 and ETCO2 were similar for the LMA Classic and LMA ProSeal during carboperitoneum and uninfluenced by the degree of obesity. In contrast, Lu et al 47, in a 2002 study of 80 adults for laparoscopic cholecystectomy, found that ETCO2 was >45 mm Hg after carboperitoneum in 20% of patients with the LMA Classic, compared with none for the LMA ProSeal. These interstudy differences may be related to higher intra-abdominal pressures used during laparoscopic cholecystectomy. Keller et al 26,in a 2002 study of 60 grossly or morbidly obese adults, found that there were no episodes of hypoxia and only one patient developed hypercarbia when the LMA ProSeal was used as a temporary airway prior to tracheal intubation. 2. Laryngeal tube airway. One study reported that gas exchange was superior for the LMA ProSeal 39 and another that it was similar 48 [see XVIII,A]. 3. Tracheal tube. One group found that gas exchange was similar for the LMA ProSeal and TT in normal patients, but was less effective in some obese patients 51 [see section XVIII,E]. 3. Work of breathing, leak fraction and dead space Work of breathing / total inspiratory resistance should be higher for the LMA ProSeal than the LMA Classic, as the airway tube is narrower and epiglottic downfolding more common. There is one study reporting that: (i) inspiratory and expiratory airway resistance are higher; (ii) peak expiratory flow lower; and (iii) the time constant is longer for the LMA ProSeal than the LMA Classic 33. These differences doubled when the LMA Classic was better positioned, and disappeared when the LMA ProSeal was better positioned, suggesting that anatomic position plays a major role in determining their resistive properties. Indirect evidence that total inspiratory resistance is similar comes from a study showing that peak airway pressures are similar for the LMA ProSeal and LMA Classic for a given tidal volume 27. Leak fraction is lower for the LMA ProSeal 11

14 LMA Analysis q Page 12 than the LMA Classic 27,35, but even at tidal volumes of 12 ml/kg it is only 2% less than the LMA Classic ( % vs 2.7%). The narrow tube tends to decrease dead space and the deeper bowl tends to increase dead space. However, there are no studies determining dead space for the LMA ProSeal. The fact that steady state ETCO2 is identical for the LMA ProSeal and LMA Classic during PPV suggests that any differences in dead space are clinically unimportant Airway protective reflexes Most studies have been conducted in paralysed patients, so provide little information about airway protective reflex activation. However, there are 3 studies in nonparalysed patients 25,35,39, 2 comparing it with the LMA Classic 25,35 and one with the LT 39. In addition, there are two studies comparing coughing during emergence versus the TT 42, LMA Classic. Brimacombe et al 25, in a study of 384 nonparalysed adults, and Cook et al 35, in a 2002 crossover study of 180 nonparalysed adults, both noted a trend to more coughing with the LMA ProSeal than the LMA Classic (3% vs 0.5%, p=0.06; 5% vs 1%, p=0.06 respectively). 2. Laryngeal tube airway. The incidence of coughing at removal is similar to the LT 39 [see section XVIII,A]. 3. Tracheal tube. The incidence of coughing at removal is less than the TT (4% vs 87% (51); 15% vs 86% 42 ) [see section XVIII,E]. 5. Hiccup One group reported a higher incidence of hiccup with the LMA Classic than the LMA ProSeal (6% vs 2%) 25. A possible explanation is that the LMA Classic may stretch the hypopharynx more vigorously than the LMA ProSeal, as more force may be transmitted along its more rigid tube, but this result may also be spurious. 6. Pulmonary defences, laryngeal function and pulmonary pathology There is no published data about pulmonary defences or laryngeal function with the LMA ProSeal. Although these are likely to be similar to the LMA Classic, it is possible that there may be differences due to variations in the pharyngeal stimulation and/or glottic compression. The incidence of aspiration and bronchospasm from 16 studies using the LMA ProSeal is 0.06% (1/1553) and 0.2% (3/1553) respectively B. There are 3 reports of aspiration associated with the LMA ProSeal. Gaitini et 12 al 48 and Koay 54 each reported a case of aspiration, but the precise circumstances were unclear. Brimacombe and Keller 55, in 2003, reported gastric aspiration with the LMA ProSeal during a laparoscopic cholecystectomy that was related to an unidentified foldover malposition. Residual gastric volume and ph with the LMA ProSeal averages 20 ml and 3.5, respectively. It has been estimated that a study of 1.3 million patients would be required to determine if the incidence of aspiration is lower for the LMA ProSeal than the LMA Classic 56. C. Gastrointestinal system 1. Oesophageal function In 1992, Vanner showed that the LMA did not interfere with upper oesophageal sphincter function. However, this finding was never verified, perhaps because of the difficulties in accessing the upper oesophageal sphincter with the LMA in position. The DT of the LMA ProSeal allows easy access to the upper oesophageal sphincter. In one of the first LMA ProSeal trials, an open upper oesophageal sphincter was identified in 2/60 patients: in one this occurred at all cuff volumes, but in the other patient it only occurred at maximum cuff volume 24. Subsequent studies showed that the incidence of upper oesophageal sphincter opening was 3-7% in paralysed patients 23,26 and 9% in nonparalysed patients 25 (Table 7). These findings raise the possibility that the LMA ProSeal might somehow trigger upper oesophageal sphincter relaxation in anaesthetised patients. This may occur mechanically, via a reflex, or by exposing it to atmospheric pressure. The LMA ProSeal does not cause relaxation of the upper or lower oesophageal sphincter in awake topicalised volunteers 18,25,27, Regurgitation and gastrointestinal reflexes Regurgitation is uncommon: the incidence from 16 studies with the LMA ProSeal is 0.06% (1/1553) C. One group reported no episodes of regurgitation in 300 patients, as determined by litmus testing of the bowl after removal 41. There are 3 reports of regurgitation without aspiration using prototype LMA ProSeal s 4,6,7 (3 cases) and 8 using the commercial LMA ProSeal 56,58-63 (11 cases). Analysis of these reports reveals that regurgitation occurred spontaneously in 6 patients 6,7,56,58-60,63, during surgical manipulation of the upper abdomen in one patient 4, and during hiccups in B Refs: 1,18,23-27,35,39-41,47,48,51-53 C Refs: 1,18,23-27,35,39-41,47,50,50-52

15 LMA Analysis q Page 13 one patient 61. Five occurred during maintenance 4,6,7,59,5 during emergence 58,62,63, and 1 during placement 61. One occurred during a percutaneous tracheostomy 56 [see section XII]. There are 3 cases where regurgitation resulted in aspiration 48,54,55 [see V,B,6]. There is no published data about the incidence of hypersalivation, retching and vomiting with the LMA ProSeal. The volume of regurgitated fluid at which aspiration occurs is lower for the LMA Classic than the LT 64. The volume of regurgitated fluid at which aspiration occurs is probably higher for the LMA ProSeal than the LMA Classic, as the bowl has a larger volume. The LMA ProSeal and streamlined liner of the pharyngeal airway (SLIPA ) but not the LMA Classic provide protection against regurgitation during PPV 65 [see VI,B,2]. One group reported that there were no differences in pharyngeal ph in patients mechanically ventilated with the LMA Classic, the LMA Fastrach, the LMA ProSeal, the LT, the cuffed oropharyngeal airway or the TT (123) [see XVIII,A]. D. Other systems There is no published data about the influence of the LMA ProSeal on intracranial, intraocular or intratympanic pressure, or the incidence of bacteraemia. It is unlikely that the influence would be any different from the LMA Classic for intracranial or intraocular pressure as these changes are linked to haemodynamic changes, which appear to be similar. Possibly, intratympanic pressures might be higher because the larger proximal cuff is closer to the Eustachian cushion. The incidence of bacteraemia may be higher due to increased difficulties with insertion and lower due to the decreased mucosal pressures. E. Physiological information The DT allows easy access to the gastrointestinal tract for monitoring physiological variables, such as cardiac output, gastric volume/ph and core temperature. In addition, the pilot balloon can be connected up to the Doyle s LMA audio monitor to monitor respiration using colour spectrogram analysis of acoustic emissions Cardiac output In a 2001 brief report, Hemmerling 67 described the successful use of a 6mm oesophageal Doppler probe passed down the DT of the LMA ProSeal in 30 patients for general surgery. Regardless of patient position, measurements of cardiac output and stroke volume were monitored throughout the procedure in all patients without additional repositioning of the probe. 2. Gastric volume/ph The GT can be used to provide information about gastric volume and ph. Mean (range) residual gastric volume for the LMA ProSeal has been reported by 5 groups: Brain et al 1, 15 ml (range 0-80); Keller et al 26, 36 ml (0-240); Lu et al ml (0-59); Evans et al 41, 24 ml (0-180); and Cook and Nolan ml (0-85). One group reported that the mean ph of gastric fluid was Another group reported an initial volume of 20 ml (0-120) and a final volume of 24 ml (0-180) Core temperature, oximetry, pressure and ph In a 2003 study of 30 adults, Mitchell et al 68 reported the successful use of a thermistor for monitoring core temperature. Other possible options for monitoring include: oesophageal oximetry 69, right and left ventricular oximetry 70 and oesophageal pressure/ph Respiratory monitoring In a 2003 brief report, Doyle 66 described the design, construction and preliminary clinical evaluation of a homemade, battery operated breath sound monitor, which can be used with the LMA ProSeal. It comprises a leak-free microphone fixed into the shortened barrel of a 3ml plastic syringe. In a study of 10 patients, it was attached to the pilot balloon of the LMA and clear, identifiable breath sounds, which were presumably transmitted from the cuff to the microphone via the inflation line, were heard in all cases. In principle, it offers advantages over the precordial stethoscope (in terms of better acoustic properties and easier placement), and over the oesophageal stethoscope (in terms of a lower risk of injury). A sample recording is available at http// VI. Function The LMA ProSeal forms a seal with the respiratory and gastrointestinal tracts, and functions as a conduit to the gastrointestinal tract, but is rarely used as a conduit to the respiratory tract, because the airway tube is too narrow (Figure 18). 13

16 LMA Analysis q Page 14 These studies also show that the seal is: 1. higher for females than males when using either a similar size (both size 4) 24,52 or a smaller size (female 4; male 5) 25,41 2. higher in obese patients 1 3. slightly higher in paralysed patients (~2 cm H2O) higher if the head and neck is rotated or flexed 23 (Table 10) 5. approximately 15 cm H2O even when the cuff is fully deflated 18,23,24 6. unaffected by GT insertion higher than the LT at low cuff volumes, but similar at high cuff volumes 39 Fig 18. Computer graphic demonstrating the seals formed with the respiratory and gastrointestinal tracts. A. Seal with the respiratory tract 1. Mechanism of seal and relationship to cuff volume The mechanism of seal, as determined by the relationship between mucosal pressure and OLP, appears to be similar to the LMA Classic 18 (Table 8). At low cuff volumes, the predominant mechanism is matching shape of the cuff and pharynx, but at high cuff volumes mucosal pressures also contribute. The pattern of changing seal with increasing cuff volume follows an exponential curve, like the LMA Classic, and begins to flatten off at half to two thirds of the maximum recommended volume 18,23,24. However, this curve is shifted upwards by around 10 cm H2O, reflecting the improved seal. 2. Seal for gas exchange a. Analysis of literature There are 17 studies: 5 descriptive 26,28,40,41,52 and 12 comparative, including 10 versus the LMA Classic D, and one versus the LT 39 (Table 9). Meta-analysis of this data reveals that the mean (range) OLP is 10 cm (5-15) H2O higher than the LMA Classic (c=182, p< ). b. Why does the LMA ProSeal form a better seal? There are 4 explanations for the improved seal. First, the broad, wedge-shaped proximal cuff may form a more effective plug in the proximal pharynx. Second, the dorsal cuff may press the ventral cuff more firmly into the periglottic tissues. Third, the parallel configuration of the airway and DT may allow the base of the tongue to cover the proximal cuff more effectively, enhancing its effectiveness as a plug. Fourth, the conical, anatomicshaped distal cuff may form a more effective seal with the hypopharynx and prevent oesophageal leaks. The relative contribution of each to the improved seal is unknown, but there is indirect evidence that the dorsal cuff only makes a modest contribution at most: firstly, the seal is more effective than the LMA Classic even when the dorsal cuff is fully deflated 18,23,24 and secondly, the paediatric sizes appear to have a high seal and yet lack a dorsal cuff Seal for prevention of soiling from above the cuff There is no published data about the efficacy of seal for prevention of soiling from above the cuff, but this should be higher than the LMA Classic, as the seal for gas exchange is higher (Figure 19). D Refs: 1,18,23-25,27,35,47,50,53 14

17 LMA Analysis q Page 15 potentially neutralising any suction component (from negative intrathoracic pressure) to the seal. Finally, the DT and oesophagus may not be neatly aligned. Fig 20. Schematic illustrating correct (A) and incorrect (B) positioning of the distal cuff in relation to the hypopharynx. If the distal cuff does not occupy the hypopharynx (H) the patient is vulnerable to aspiration if regurgitation occurs. E=epiglottis. C=cuff. T=trachea. DT=drain tube. Fig 19. The author submerged in the bathtub with an LMA ProSeal in situ illustrating the efficacy of the cuff to protect the airway from fluid in the mouth and upper pharynx. There is no danger of aspiration from above the cuff provided that the depth in cm is less than the oropharyngeal leak pressure in cm H2O. B. Seal with the gastrointestinal tract The seal formed by the distal cuff with the hypopharynx is conceptually simple, with the conical cuff fitting neatly into the conical hypopharynx, and the DT and oesophagus neatly aligning themselves with one another; however, in reality, the hypopharyngeal seal is complex, dynamic, potentially delicate and poorly understood. First, the sealing area is small and slight proximal movement (approx. 0.5cm) can result in a slight reduction in seal, and modest proximal movement (approx. 2cm) can result in complete loss of seal as the distal cuff slips back into the laryngopharynx (Figure 20). Second, the hypopharynx surrounding the distal cuff is a muscular sack that is prone to changes in tone. Third, the distal cuff probably penetrates the upper fibres of the upper oesophageal sphincter, which are prone to marked changes in tone. Fourth, the pyriform fossae can open up during PPV 22, and the oesophageal mucosa can lift off the distal aperture during spontaneous ventilation 21. Fifth, the upper oesophagus is open to atmosphere, 1. Mechanism of seal The mechanism of seal with the hypopharynx is likely to be a combination of matching shape and mucosal pressure, as hypopharyngeal mucosal pressures are lower than the pressure at which fluid passes from the oesophagus to the pharynx (2-11cm H2O vs 16-73cm H2O) 18, and the efficacy of seal increases with cuff volume 71. Liquid flow between the oesophagus and pharynx occurs at progressively higher oesophageal pressures for the LMA ProSeal, but not the LMA Classic suggesting that mucosal pressure has a more important role in the mechanism of seal at high cuff volumes. 2. Efficacy of seal Hypopharyngeal leak pressure (the pressure at which air or fluid passes between the hypopharynx and upper oesophagus) has been determined by measuring the airway pressure at which air leaks into the oesophagus in anaesthetised adults 24,47, or the oesophageal pressure at which fluid leaks into the pharynx with the DT clamped in fresh cadavers 71. The efficacy of seal for air is at least 27-29cm H2O 24,47, and for fluid is 19-73cm H2O, depending on cuff volume 71 (Table 11). Less useful information about the hypopharyngeal seal comes from a study of 102 anaesthetised adults where the DT was filled with methylene blue dye and none was seen within the bowl, demonstrating that the hypopharyngeal leak 15

18 LMA Analysis q Page 16 pressure is at least 12cm H2O 72. There is a laboratory study providing indirect evidence that the LMA ProSeal and SLIPA form a better seal with the hypopharynx than the LMA Classic 65 [see section XVIII,D]. 3. Gastric insufflation and distention There are 2 case reports 21,73 and 12 studies E. 1. Case reports. Brimacombe et al 73, in 2001, reported gastric distention in association with the foldover malposition and PPV during a laparoscopic cholecystectomy. One group reported gastric distention in association with a partially obstructed airway and oesophageal breathing 21 [see III,D]. 2. Studies. These show that the incidence of gastric insufflation: (i) is around 0.1% (1/1105); (ii) during high airway pressure ventilation remains low, for example, one group detected no episodes of gastric insufflation in 60 grossly or morbidly obese adults during PPV at 12 ml/kg tidal volume or even during static OLP testing at 32±8 (12-40) cm H2O 26 ; (iii) during normal airway pressure ventilation is similar to the LMA Classic 47,LT 39 and LTS 74 ; and (iv) during high airway pressure ventilation is probably lower than the LMA Classic (0% vs 7.5%) 47 and LT (0% vs 3%) 39. C. Conduit to the respiratory tract The internal diameter of the LMA ProSeal airway tube is smaller than the LMA Classic and LMA Fastrach, making it less suitable for passing instruments into the respiratory tract. Nonetheless, fibreoptic scopes and small TTs will pass down the airway tube (Table 3). While there are many reports of successful passage of fibreoptic scopes to assess anatomic position [see section IV], there are only two reports of intubation via the LMA ProSeal. One group reported indirect tracheal intubation using a fibreoptically placed guide wire and an airway exchange catheter in a patient for a hemicolectomy 34. Another reported using the LMA ProSeal for fibreoptic-guided intubation using a size 6.0 cuffed TT after airway rescue in the intensive care unit 75. D. Conduit to the gastrointestinal tract When the distal cuff is correctly positioned, the DT and oesophagus are in direct alignment and instrumentation can be passed into the gastrointestinal tract. The best method of achieving perfect alignment is to use the GEB-guided technique. The most common instrument passed down the DT is the GT, but instruments for physiological monitoring can also be inserted [see section IV,E]. It should also be possible insert a gastric balloon tube to reduce still further the risk of aspiration 76. The success rate for GT insertion is 96% [880/918] F with a mean insertion time of around 15s 24,25. Martínez- Pons and Madrid 77, in 2004, reported easier GT insertion if the DT was primed with an 18F GT prior to LMA ProSeal insertion (first-time success rate improves from 91% to 100%). Brimacombe et al 78, in 2004, reported no failed GT insertions in over 3000 patients after laryngoscope-guided, GEB-guided insertion. This is not unexpected, as the GEB perfectly pre-aligns the DT with the oesophagus. The success rate for insertion of a thermistor 68 and transoesophageal echocardiograph 67 is 100% from 2 small studies. Probably the most common cause of failed insertion is folding over of the cuff and compression of the DT 73. This occurs in 3.4% (95/2806) of patients 79 using the digital or IT techniques, but cannot occur with the GEB-guided technique. There is one study comparing GT insertion between the LMA ProSeal and LMA Classic, which reported that it was more successful (88% vs 55%) and quicker (22±18 s vs 38±56 s) with the LMA ProSeal than the LMA Classic 25. Instruments should not be passed blindly down the DT if there is an air leak from the DT, as this strongly indicates malposition. One group reported failed insertion of a GT with the LMA ProSeal due to a herniated cuff that was compressing the DT from behind 80 [see section XVII,B]. VII. Pre-anaesthesia phase The pre-anaesthesia phase follows a similar pattern to the LMA Classic, but the pre-use check tests are more extensive, as the LMA ProSeal is a more complex device. E Refs: 1,24-27,35,39,41,47,50-52,74 F Refs: 1,24-26,28,35,47,50,53 16

19 LMA Analysis q Page 17 A. Pre-use check tests All the general and cuff inspection tests performed on the LMA Classic should be performed and in addition: 1. the DT should be assessed for patency, transparency and mobility 2. the support ring for the distal DT should be palpated for integrity 3. the patency of the distal DT should be verified with the cuff fully inflated 4. the accessory vent should be patent and contain no foreign bodies 5. the airway tube should be checked for loose wires 6. the integral bite block should be firmly adherent to the airway tube and DT 7. the airway tube and DT should be fused together along their entire lengths 8. the finger strap should be intact and contain no foreign material 9. the dorsal cuff should start to inflate when the ventral cuff is semi-inflated 10. the proximal end of the cuff should sit in the bucket shaped finger strap 11. the IT should not be distorted and the silicone backing intact B. Indications and contraindications The indications are the same as for the LMA Classic, but the LMA ProSeal is preferable whenever a better seal, better airway protection and access to the gastrointestinal tract is required (Table 12). The author considers that these advantages are desirable in all patients, and the LMA ProSeal should therefore replace the LMA Classic and LMA Unique. The LMA ProSeal is contraindicated in patients who are at risk of aspiration during induction of anaesthesia, or who have oropharyngeal pathology / anatomy that might interfere with insertion (difficult if mouth opening < 20mm). The LMA ProSeal is not contraindicated in patients who are at risk of aspiration after induction, provided it is correctly positioned G. It is relatively contraindicated for intraoral surgery, since it cannot easily be moved from side-to-side, the DT could be occluded by tonsillar gag, and the larger proximal cuff might interfere with the surgical field. In this situation, the LMA Flexible is preferable. However, the LMA ProSeal tubes can be moved forwards and backwards, DT compression can be avoided by inserting a thick GT and the cuff need not interfere with the surgical field. Finally, the LMA G The opinions in this publication are those of the author and may not reflect the Laryngeal Mask Company Limited s indications or instructions for use for these devices. ProSeal is relatively contraindicated as an airway intubator due to its small internal diameter airway tube, although passage of a small TT or airway exchange catheter is feasible 34,75. In this situation, the LMA Fastrach is preferable. C. Size selection The manufacturer recommends a weight-based formula similar to the LMA Classic (size 3 for adults/children, kg; the size 4 for normal adults, kg; and the size 5 for large adults, kg), but most studies have used the sex-based formula commonly used with the LMA Classic (size 4 for females; size 5 for males). There is some evidence that the size 4 is too small for the average male, as the seal is about 5cm H2O lower than in females 24,52. A weight-based formula of size 4 for kg and size 5 for > 80 kg has also been successfully used with the LMA ProSeal 39. There are 2 studies determining size selection: one study compares different sizes in males and females 81 and the other compares a weight-based versus a sex-based size selection formula Males and females. Kihara and Brimacombe 81, in a 2003 study comparing: (i) the size 4 and 5 LMA ProSeal in 30 males; (ii) the size 3 and 4 LMA ProSeal in 30 females; and (iii) the size 4 versus size 5 LMA ProSeal in 30 females, in terms of ease of insertion, OLP, ventilation, gas exchange, fibreoptic position, mucosal injury, found that the size 4 LMA ProSeal is preferable for females (easier insertion than size 5, better OLP than size 3), and the size 5 LMA ProSeal is preferable for males (better OLP than size 4). 2. Weight vs gender-based formula. Kihara et al 82, in a 2003 study of 237 adults, found that size selection for the LMA ProSeal is equally effective using the manufacturer s weight-based formula (size 3 for <50 kg, size 4 for kg and size 5 for >70 kg) and the sex-based formula (size 4 for females and size 5 for males), in terms of ease of insertion, ventilation, gas exchange, fibreoptic position, mucosal injury and postoperative pharyngolaryngeal complaints, but OLP was higher with the sex-based formula due to the more frequent selection of larger sizes. VIII. Placement phase The placement phase is similar to the LMA Classic, but there are differences in the equipment required (IT, GT and GEB), the insertion techniques, the clinical tests for malposition, and the frequent use of a GT. 17

20 LMA Analysis q Page 18 A. Co-induction / induction agents and depth of anaesthesia There are no studies specifically determining the dose of anaesthesia agents. Most studies involve insertion after muscle relaxation and provide no useful information. However, data from the only non-crossover study where the LMA ProSeal was inserted without muscle relaxants suggests that the dose of co-induction (midazolam/alfentanil) and induction (propofol) agents are similar to the LMA Classic 25. It is likely that the depth of anaesthesia required for LMA ProSeal insertion is similar to the LMA Classic, but this has not been tested. B. Insertion theory The principles of LMA ProSeal insertion are similar to the LMA Classic, but the practice is slightly different. The semi-flexible, double-tube arrangement provides lateral but not anteroposterior stiffness and the amount of force that can be transmitted along the tube is intermediate between the LMA Classic and LMA Flexible. As a rule of thumb, the tube is too floppy to push the cuff around the oropharyngeal inlet into the laryngopharynx, but sufficiently stiff to push it towards the hypopharynx, once it has entered the laryngopharynx. The softer backplate makes the cuff more likely to fold over. The bulkier deflated cuff reduces the space in the mouth for digital manipulation and makes epiglottic downfolding more likely. C. Insertion techniques There are 3 primary insertion techniques for the LMA ProSeal : (i) the digital technique; (ii) the introducer technique; and (iii) the laryngoscope-guided, GEB-guided technique H. The only alternative insertion technique described to date is the use of Dingley s artificial hard palate insertion tool 83. Since perfect positioning is essential for the LMA ProSeal to function correctly and safely, adherence to the recommended insertion techniques may be more important than for other LMA devices. 1. Digital This is similar to LMA Classic insertion except that a slight lateral approach is required more frequently, and the index finger is placed under the insertion strap. There are two variations: (i) the midline approach; and (ii) the lateral approach. Gloves should be worn during insertion, and removed and invaginated after insertion to 18 prevent cross-infection 84. This insertion technique is illustrated in the instruction manuals and text book 85. a. Midline approach This can be divided into four phases. Phase 1 The neck is flexed on the chest and the head extended on the neck using the non-dominant hand cupped behind the occiput. The LMA ProSeal is held at the double-tube/mask junction between the index finger in the insertion strap and the thumb posteriorly, as if holding a pen. The wrist and finger joints should be partially flexed, as they would be for writing, since this is the position from which maximum control of fine cuff movement is possible. Phase 2 The mouth should be opened gently, either by an assistant, or by using the fingers of the dominant hand that are not holding the tube. These fingers can also be used to sweep away lips that become trapped between the cuff and teeth. If required, the non-dominant hand can be used open the mouth, position the cuff against the hard palate and sweep away lips, but it must return to the occiput to flex the neck and extend the head before the cuff is advanced into the oropharynx. A clear view of the entire oral cavity should be obtained by leaning over the patient s head and looking upwards into the mouth. The layout of the mouth should be examined carefully to determine how best to position the cuff. Factors influencing the way this is done include the state of dentition, the degree of mouth opening, the location/ size of the tongue and the shape of the hard palate. Phase 3 The lubricated cuff is positioned on the hard palate in the midline and completely flattened against it. This can be accomplished in two ways: (i) the distal cuff can be flattened just behind the incisors and the cuff advanced along the curve of the hard palate into position; or (ii) the entire cuff can be inserted straight into the mouth and then manipulated into position. Care should be taken to ensure that the cuff rim is flattened against the hard palate with no folding. This may necessitate partial withdrawal of the cuff from the mouth and/or digital manipulation of the cuff rim at the level of the incisors or within the mouth. Once flattened against the hard palate, the thumb is no longer needed to hold the tube as the position is maintained by upward pressure from the index finger. At this stage, only the tip of the index finger H The opinions in this publication are those of the author and may not reflect the Laryngeal Mask Company Limited s indications or instructions for use for these devices.

21 LMA Analysis q Page 19 needs to be in contact with the tube. Furthermore, the index finger should emerge from the mouth lateral to the tube, not anterior to it. This is because if the entire finger is anterior to the tube, and particularly if the joints are flexed, the posterior surface of the finger will press into the lower teeth during insertion, limiting their use for manoeuvring the mask and putting the dorsum of the finger at risk of trauma. Before advancing the LMA ProSeal, the lips should again be checked to ensure that they are not trapped between the double-tube/cuff and the teeth. Phase 4 Once the head, neck and cuff are correctly positioned, the LMA ProSeal is slowly advanced along the palatopharyngeal curve. This is accomplished by maintaining continual centrifugal pressure into the curve, and a slight forward motion along the curve. As the device moves initially posteroinferiorly and then inferiorly, the index finger is extended and the wrist internally rotated. If required, insertion can be completed by pushing the proximal end of the LMA ProSeal airway tube with the non-dominant hand. When the cuff can be advanced no further, the finger is withdrawn and the cuff inflated. To avoid dislodging the LMA ProSeal, the end of tube is held until the index finger has been withdrawn. The mouth should not be opened excessively when the device is pushed into the laryngopharynx, because this will force the tongue and epiglottis to drop posteriorly and reduce the anteroposterior diameter of the pharynx. b. Lateral approach The lateral approach is identical to the midline approach except that the cuff is not placed symmetrically across the hard palate, but rather placed across it at an angle of approximately 45 with the proximal end pressed against one side and the distal end pressed against the other. The cuff is advanced into the oropharynx with its lateral distal side as the leading edge, and then straightened out once in the laryngopharynx. The advantage of the lateral approach is less resistance at the back of the mouth; this is because the lateral distal cuff is firmer and has a smaller turning radius. Another potential advantage of the lateral approach is that the distal cuff might avoid impaction with midline pharyngeal structures such as the epiglottis and glottis. It has two theoretical disadvantages. First, the tonsils will be traversed more frequently and this might lead to trauma. Second, if the cuff is not straightened, there may be some residual rotation, and this might increase the risk of malposition. In clinical practice, neither of these problems has been reported. The lateral approach can be used as the primary insertion technique, or if resistance is encountered at the back of the mouth using the midline approach. In this latter situation, the cuff can be easily shifted into position for a lateral approach without withdrawing it from the mouth, or releasing it from the hard palate. 2. Introducer tool The IT is attached by inserting its distal end into the retaining strap, folding the airway and DTs around its convex surface, and clipping the airway tube into the proximal matching slot (Figure 21). The insertion technique is similar to LMA Fastrach insertion except the head and neck is usually in the sniffing rather than the neutral position (Figure 22A-C). The advantages are that it allows finger-free insertion and perhaps facilitates insertion from unconventional operator positions, such as to the front or side of the patient. The IT is removed after use by unclipping it from the airway tube and reverse rotating it out of the pharynx while stabilising the LMA ProSeal with the non-dominant hand (Figure 22D). Fig 21. Schematic illustrating attachment of the introducer tool. A. Place the tip of the introducer into the strap. B. Fold the tubes around the introducer and fit the proximal end of the airway tube into the matching slot. C. The introducer tool in position. 19

22 LMA Analysis q Page 20 the oesophagus and always inserting under direct vision should eliminate the risk of oesophageal trauma. There are three GEB techniques. a. Primary technique Fig. 22 Schematic of introducer tool insertion technique [see VIII,C,2]. 3. Laryngoscope-guided, GEB-guided This was first described by Howarth et al 86 in 2002 and involves railroading the LMA ProSeal DT along a GEB placed in the proximal oesophagus under direct vision. It has seven advantages: 1. it allows the distal cuff to be guided into its correct position in the hypopharynx 2. it minimises impaction at the back of the mouth 3. folding over of the cuff cannot occur 4. it is compatible with finger-free insertion 5. it allows unexpected oropharyngeal pathology to be identified 6. it provides information about ease of intubation 7. tests for the position and patency of the DT are not necessary, as it is always correctly placed The disadvantages are the potential for stimulation and trauma 87. It is relatively contraindicated in patients with upper oesophageal disease. Drolet and Girard 88, in 2001, and Brimacombe et al 89, in 2002, described a similar technique using a GT and fibreoptic scope, respectively. An advantage of the GT is that it is potentially less traumatic than the GEB; however, a GT may not be sufficiently stiff to guide the LMA ProSeal around the oropharyngeal inlet. An advantage of the fibreoptic scope is that it obviates the need for laryngoscopy. The author recommends that the GEB technique should be used as a backup given the current lack of data about safety and efficacy I, but considers that future studies will see this technique promoted to a first line technique in many situations. Avoiding force during passage of the GEB into I The author and colleagues have used the GEB-technique in over 6000 patients without any evidence of minor or major oesophageal injury. Occult blood is rarely detected on the GEB after removal. The DT is primed with a lubricated GEB with its straight end first, leaving the 5cm bent portion protruding from the proximal end for the assistant to grip, and the maximum length protruding from the distal end for the operator to manipulate (Figure 23). Under gentle laryngoscope-guidance (no need to see vocal cords other than to assess ease of LG-TI), the distal portion of the GEB is placed 5-10cm into the oesophagus while the assistant holds the LMA ProSeal and proximal portion of the GEB (Figure 24A-C, Figure 25). The laryngoscope is carefully removed. The LMA ProSeal is inserted using the digital insertion technique while the assistant stabilises the proximal end of the GEB so it does not penetrate further into the oesophagus (Figure 24D-F). The cuff is inflated and the anaesthesia breathing system is attached and supported by the assistant (Figure 24G). Ventilation is commenced and the LMA ProSeal is fixed to the face (Figure 24H). The GEB should not be removed until fixation is complete, as it can act as a guide to reinsertion in the event of displacement, but when it is removed the LMA ProSeal should be held to prevent displacement. Fig 23. The gum elastic bougie (GEB). A. View of the middle portion with depth markers and specifications. B. The LMA ProSeal with the GEB mounted inside the drain tube. The straight end is distal (C) and the bent end proximal (D). Note that the GEB should be inserted into the drain tube such that the bend just protrudes from the proximal drain tube, rather than equal lengths protruding from the distal and proximal ends. 20

23 LMA Analysis q Page 21 b. Other techniques There are two variations. First, the position of the laryngoscope can be maintained during insertion. The potential advantage is that it might reduce the risk of epiglottic downfolding, as has been shown with the LMA Classic 90. Second, if the GEB is already in the oesophagus, such as might occur during failed LG-TI, the distal end of the DT can be quickly lubricated and then threaded over the bougie until it protrudes from the proximal end and then insertion can take place. D. Insertion success rates There are 18 studies: 5 descriptive 26,40,83,91 and 15 comparative J from a meta-population of 1399 patients (Table 13). The mean (range) first-time and overall success rate is 87% (81-100) and 99% (91-100), respectively. These studies also show that the: Fig 24. Photo sequence for laryngoscope-guided, gum elastic bougie-guided insertion of the LMA ProSeal [see VIII,C]. Fig 25. Laryngoscopic view of the gum elastic bougie entering the hypopharynx. It is only necessary to see the posterior portion of the vocal cords to direct the bougie into the oesophagus. Force must never be used when inserting the bougie. 1. first-time success rate is lower for the LMA ProSeal than the LMA Classic (84% vs 91%, p=0.0001), but overall success is similar (both: 98%) 2. time to achieve an effective airway is longer with the LMA ProSeal than the LMA Classic (p= ) 3. insertion of the LMA ProSeal is easier than the LMA Classic during manual-in-line stabilisation using the IT technique 93 [see section XIII] 4. insertion success is greater for the LMA ProSeal than the LT (100% vs 92%) muscle relaxation does not improve insertion success 41. One group reported a higher first time success rate with the IT 24, but 2 larger studies detected no differences 35,41. The highest insertion success rates are with the laryngoscope-guided, GEB-guided technique: both Brimacombe et al 91 and Howarth et al 40 reported 100% success at the first attempt with perfect positioning. There is one study showing that GEB technique is better than the digital or IT techniques 94. In a 2003 study of 240 adults, Brimacombe et al 94 found that: (i) insertion was more frequently successful with the GEB-guided technique at the first attempt (GEB 100%, digital 88%, IT 84%), but success after 3 attempts was similar (GEB 100%, digital 99%, IT 98%); (ii) the time taken to successful placement was shorter with the GEB-guided J Refs: 1,18,21,23,24,25,27,35,38,39,41,47,53,92,93 21

24 LMA Analysis q Page 22 technique (GEB 25±14 s, digital 33±19 s, IT 37±25 s); (iii) there were no differences in the frequency of visible blood, but occult blood occurred less frequently for the GEB-guided technique (GEB 12%, digital 29%, IT 31%); and (iv) there were no differences in post-operative airway morbidity. Matioc and Arndt reported a 10/10 success rate using Dingley s artificial hard palate 83. Insertion is feasible in awake volunteers 57, fresh cadavers 38 and in morbidly obese patients 26. Failure to insert into the pharynx and air leak appear to be the main causes of failure 18,24,41, but failure to form a clear passage to the trachea also occurs 20. If the LMA ProSeal fails due to air leak up the DT despite correct positioning, insertion of a smaller size may solve the problem by allowing the distal cuff to penetrate more deeply into the hypopharynx 95. The bigger is better rule does not always apply to the LMA ProSeal. E. Cuff inflation and fixation The cuff volume required to form an effective seal with the respiratory tract is lower than the LMA Classic 18. An adequate seal can be obtained in most patients with no air in the cuff. However, the cuff should be inflated with at least 25% of the maximum recommended volume to ensure an effective seal with the gastrointestinal tract for prevention of aspiration and gastric insufflation 71. The cuff volume required to achieve a specific intracuff pressure is higher than the LMA Classic, as the cuff is larger. Evans et al 41 reported that the mean (range) cuff volume to achieve an intracuff pressure of 60 cm H2O was 28 ml (14-45 ml) for the size 4 in females, and 37 ml (18-63 ml) for the size 5 in males. Correct fixation is critical as small proximal movements can result in loss of seal between the distal cuff and hypopharynx 22. The author recommends that both maxillary and mandibular tapings are employed to ensure reliable fixation. Stix et al 22, in 2002, noted that securing the LMA ProSeal with moderate longitudinal force along the airway tube improved the seal with the hypopharynx. F. Malposition Malposition occurs in approximately 5-15% of patients at the first attempt (unless the GEB-guided technique is used), but most are easily recognised and corrected. Six malpositions (approximate incidence) have been described: (i) distal cuff in laryngopharynx (7%) 1 ; (ii) distal cuff in glottic inlet (3%) 1 ; (iii) distal cuff folded over (3.4%) 79 ; (iv) severe epiglottic downfolding (<0.5%) 25 ; (v) glottic compression (0.3%) 36 ; and (vi) anterior flexion 96 (only described once). Glottic compression is not strictly a malposition, but presents as such and will be discussed here. The diagnostic signs are presented in Table 14. There is one study looking at bite block position as an indicator of correct position. In a 2003 study of 274 adults, Stix and O Connor 97 found that when the LMA ProSeal was correctly positioned, the midway point of the bite block was proximal to the incisors in 78% of women (95% CI, 71-85%) and 92% of men (95% CI, 87-97%) (Figure 26). The standard deviation for the depth distribution in men and women was 1.0 and 0.8 cm, respectively. Fig 26. View of the bite block between the teeth (arrow). The location of the mid-portion of the bite block relative to the incisors provides information about malposition. 1. Distal cuff in laryngopharynx or glottic inlet When the LMA ProSeal is not inserted deeply enough, the distal cuff will sit in the laryngopharynx; correction usually requires pushing it in further (Figure 27A, B). When the LMA ProSeal takes an anterior path during insertion, the distal cuff will collide with the glottic inlet and either remain there (Figure 27C), or fall back into the laryngopharynx; correction usually requires reinsertion using a lateral approach, or the GEB-guided technique. To distinguish between inadequate depth of insertion and glottic impaction, the LMA ProSeal can be pushed further inwards: the former will usually be corrected and the latter made worse, with increased airway obstruction or airway protective reflex activation. O Connor and Stix 98 have suggested that these malpositions can also be distinguished using the soap bubble test (Table 14). 22

25 LMA Analysis q Page 23 Fig 27. Schematic illustrating three common malpositions. A. Correct position. B. Distal cuff mid-laryngopharynx. C. Distal cuff in glottic inlet. D. The distal cuff folded over. 2. Distal cuff folded over Folding over occurs when the distal cuff impacts against the posterior oropharyngeal wall 73 (Figure 27D; Figure 28A-D). Starting with the distal rim, the cuff folds up underneath the advancing cuff until the unfolded proximal cuff is redirected inferiorly into the laryngopharynx by the build up of folded cuff in the oropharynx. Once folded, the distal cuff cannot easily unfold because it is wedged into the laryngopharynx. Folding over has been reported with the LMA Classic 99, but is probably more common with the LMA ProSeal, as the backplate is softer. Brimacombe et al 79, in a brief descriptive study of 95 patients with the foldover malposition, found that in 92% resistance was encountered at the back of the mouth, in 83% the bite block protruded from the mouth and in 98% (93/95) ventilation was unaffected and the seal was normal. The main danger of the foldover malposition is that the LMA ProSeal cannot prevent aspiration or gastric insufflation, yet high airway pressures are still possible, increasing the risk that these problems will occur. The author considers that the patency of the DT must be assessed in all patients with the LMA ProSeal to exclude this malposition. Where passage of a GT is not required, the patency can be tested by noninvasively passing the GT only to the end of the DT (Table 3). Several techniques have been used to correct this malposition including: (i) reinsertion using a lateral approach; (ii) reinsertion with the DT stiffened with a stylet; (iii) guided insertion with a GEB; and (iv) digital correction by sweeping a finger behind the cuff. Of these, (i) and (iii) appeared to be the most effective. Folding over cannot occur with the GEB-guided insertion technique. Fig 28. A. The foldover malposition demonstrated manually. B. With this malposition it is not uncommon for the entire bite block to remain outside the mouth. C. Fibreoptic view from the airway tube. The drain tube (DT) and tip of the mask are folded posteriorly behind the bowl of mask. The proximal portion of the cuff rests in the vallecula and the epiglottis is visible. D. More proximal fibreoptic view. The DT bends backwards behind the bowl of the mask against the posterior pharyngeal wall (PPW). An unprotected airway exists under the epiglottis. Photos (except A) courtesy of Ewan Cameron, Michael Stix, and Cornelius O Connor Jr. 3. Severe epiglottic downfolding Severe epiglottic downfolding occurs when the epiglottis in dragged inferiorly by the cuff and completely covers the glottic inlet (Figure 29). In principle, this is more likely to occur if: (i) the cuff is inflated pre-insertion; (ii) the pharynx is compressed during insertion, such as by excess mouth opening; and (iii) if the epiglottis is enlarged or floppy. To correct this, the LMA ProSeal should be reinserted with the head and neck in a more extreme sniffing position, and/or with jaw thrust applied and/or with the epiglottis elevated using maintained laryngoscopy. 23

26 LMA Analysis q Page 24 Fig 29. Epiglottic downfolding. This can cause complete airway obstruction, but in this case the patient had a patent airway. Photo courtesy of Chris Keller. 4. Glottic compression Glottic compression occurs when the glottic inlet is mechanically compressed by the distal cuff. In principle, it is more likely to occur when the pharynx is small, the cuff over inflated and the distal cuff pressed into the hypopharynx with excess force. To correct this, air should be withdrawn from the cuff, and the anteroposterior diameter of the pharynx increased by adopting the sniffing position and/or applying jaw thrust. Reinsertion does not usually solve this problem. 5. Anterior flexion In 2003, Garcia et al 96 described a new malposition: anterior flexion of the cuff. It occurs when the cuff is directed into the anterior pharyngeal wall by the IT and the cuff folds over such that the distal portion lies across the bowl (the opposite of the usual foldover malposition). In this situation, there will be airway obstruction and DT failure. Correction involves reinsertion using a different technique, preferably the GEB-technique. G. Drain tube 1. Air leaks An air leak up the DT during PPV demonstrates that the lumen of the DT is in continuity with the airway tube, and therefore the gastrointestinal and respiratory tracts are not isolated from one another. The airway pressure at which air leaks occur indicates the degree of isolation. Air leaks up the DT at high airway pressures are compatible with a correctly placed LMA ProSeal, but an air leak at low airway pressures usually suggests malposition, or occasionally the wrong size. Large volume air leaks can be readily detected by listening over the DT, or feeling the air with a hand, but small volume air leaks are best detected by injected a short column of water-based lubricant into the DT (Figure 30A-C), or, better still but less conveniently, by placing a soap bubble over the end of the DT using a ring applicator 100 or finger 101. By careful observation of the lubricant or soap bubble membrane, very small changes in intra-drain tube pressure can be detected (Figure 31A-C). The lubricant or membrane can usually be seen to move back and forth during PPV since some of the DT passes within the bowl. A gauze thread can also be used to detect air leaks 100. Occasionally air leaks up the DT will be caused by release of air from the stomach 21. Air leaks down the DT can occur if negative intrathoracic pressures develop such as during partial airway obstruction 21,49, or hiccup 61. Fig 30. Drain tube leak tests. A. The lubricant is injected 2-3 cm into the drain tube. The lubricant nozzle fits flush with the proximal aperture of the drain tube for easy injection. B. The upper (red arrow) and lower (white arrow) ends of the lubricant column bulging slightly due to a slight increase in drain pressure, in this case during a suprasternal notch tap test [see Figure 32]. C. A small quantity of air is seen escaping from the drain tube (green arrow). Fig 31. A ring for blowing soap bubbles can be used to apply a soap membrane across the proximal end of the drain tube (A). Careful observation of this membrane will allow extremely small changes in drain pressure to be detected (B,C). For example, if the drain tube is sitting in the glottic inlet, cardiac pulsations can be seen. 24

27 LMA Analysis q Page Patency The DT must be fully patent for the LMA ProSeal to be used safely. If the DT is not fully patent, the LMA ProSeal : (i) cannot protect against gastric insufflation and pharyngeal regurgitation; (ii) GT placement will be impossible; and (iii) some of the tests of malposition will be unreliable, leading to a false sense of security. A lack of air leak up the DT does not guarantee that it is patent because of the foldover malposition [see F]. Small volume air leak (detectable by lubricant, soap bubble or thread) does not guarantee that the DT is fully patent as these tests are so sensitive that leaks can occur if only a small portion of the tube is patent. Large volume air leaks up the DT indicate that the DT is patent, but that it is also malpositioned. There are two tests of DT patency: (i) passage of instruments (GT, fibreoptic scope, lightwand), and (ii) the suprasternal notch tap test. a. Passage of instruments Gastric tube Passage of a GT down the DT is the simplest, most readily available test of DT patency, and is essentially 100% reliable. An appropriate size must be chosen and it should be well lubricated. Provided the GT is not passed beyond the distal aperture, the test can be entirely noninvasive. DT lengths are given in Table 3. Fibreoptic scope Passage of a fibreoptic scope is simple and 100% reliable as it depends on the successful physical passage of the fibreoptic scope combined with visual confirmation of patency. Lightwand In 2004 Christoudoulou 102 described the use of a Trachlight lightwand to detect the foldover malposition. The Trachlight lightwand is marked in 1cm increments and meets resistance 1-2 cm from the tip if the tip is folded over. A dull glow in the anterior neck with passage of the lightwand beyond the DT tip may indicate correct alignment of the LMA ProSeal with the upper oesophageal sphincter. The disadvantages are: (i) the potential for stimulation and trauma if the bulb protrudes beyond the end of the DT and it is not aligned with the upper oesophageal sphincter; and (ii) it cannot be used with the paediatric sizes of LMA ProSeal, as it is too large 103. Another option might be to insert the Trachlight to the distal end of the DT before LMA ProSeal insertion, to prevent the cuff folding over and to provide information about position once inserted - in principle, the light glow should be seen at the level of the cricoid cartilage if it is sitting correctly in the hypopharynx. b. Suprasternal notch tap test or Brimacombe bounce The suprasternal notch tap test or Brimacombe bounce (coined by a group of SE Asean anaesthesiologists, who witnessed numerous demonstrations of the tap test by the author in August 2002) was first described by O Connor et al 104 in It involves tapping the suprasternal notch or cricoid cartilage, and observing simultaneous movement of a column of lubricant, or a soap bubble membrane, at the proximal end of the DT (Figure 32). Both of these structures lie in close proximity to the hypopharynx, where the correctly placed distal cuff sits. For the test to be positive, the DT must be patent from within the distal portion that travels though the distal cuff to the proximal end open to atmosphere. The test works by cuff compression causing DT compression within the distal cuff. A pressure wave is set up within the DT, which moves the lubricant or soap bubble membrane. O Connor et al 104 reported a low false negative rate for the suprasternal notch tap test in 50 adults, but false positives and negatives can occur. False positives can occur if the last 1-2 cm of the DT is folded over and some of the DT is still patent within the distal cuff 105. False negatives can occur if the oesophagus is open, as this can weaken the pressure wave. Fig 32. Suprasternal notch tap test or Brimacombe bounce. The suprasternal notch or cricoid cartilage is tapped (green arrow) while looking for simultaneous movement of the lubricant column or soap bubble membrane at the proximal end of the drain tube (red arrow). 25

28 LMA Analysis q Page 26 H. Gastric tube insertion 1. When to insert The advantages of inserting a GT are that: 1. it allows removal of gas/fluid from the stomach 2. the process of insertion provides information about the position/patency of the DT 3. it can function as a guide to reinsertion if accidental displacement occurs 88 The disadvantages are that: 1. there is the risk of tracheal placement 2. there is a risk of trauma 3. the presence of the GT may trigger regurgitation by interfering with oesophageal sphincter function 4. the GT blocks the DT so that gas and fluid cannot escape from the oesophagus Since most patients have some residual gastric fluid 106, an argument can be made for inserting a GT in all patients; however, the risks of trauma are unknown and the GT cannot reliably empty the stomach unless, perhaps, the patient is inconveniently rotated through 360. The two main contraindications to GT insertion are malposition (as it can enter the glottis) and upper oesophageal disease (as pathology can be worsened). An inconvenience of GT insertion is that it cannot easily be left in the stomach after LMA ProSeal removal, as the proximal end will not fit down the DT. This problem can be overcome by cutting and splicing it back together with tape. It would be easy to design a GT with a detachable proximal end. If a nasogastric tube is required postoperatively, it is perhaps best inserted postoperatively. Although the nasogastric tube could be inserted before LMA ProSeal placement or behind the cuff after placement, it might influence the hypopharyngeal seal, although this has not been tested. The success rate for GT insertion is 96% [see section VI,D]. 2. How to insert a. Size selection and preparation The correct size of GT must be selected (Table 3). There can be subtle differences in the external diameter and shape of the same-sized GTs, but if in doubt the fit can be verified before the LMA ProSeal is inserted. However, it is not necessary to choose the maximum size that will fit. Smaller sizes have the advantage of leaving the DT semi-patent to allow safe venting of fluid or gas in the oesophagus. b. Insertion The GT should be well lubricated with a water-based gel (Figure 33A-C). A convenient, minimal-mess method is to inject a 2-3cm column of lubricant into the DT. The GT is moved up and down in the proximal half of the DT to smear the lubricant around. The DT should be held upright while the GT is inserted. There is slight resistance as the GT negotiates the two bends within the cuff: first where it swerves medially as it enters the proximal bowl; and second where it swerves anteriorly to enter the distal ventral cuff. There is occasionally slight resistance as it pushes the hypopharyngeal mucosa aside and enters the oesophagus. The next resistance that is encountered is when it impacts against the stomach wall. Force must never be used and GT insertion should never be attempted if large volumes of air are leaking up the DT. If marked resistance occurs, the DT is either folded over (highly likely) or impacting in the hypopharynx/oesophagus (high unlikely). Occasionally, movement can be seen in the suprasternal notch area when resistance is encountered in the hypopharynx. It is easy to diagnose the cause of resistance by noting the depth at which it occurs. If marked resistance is encountered, the LMA ProSeal should be removed and reinserted. Alternatively, the problem can be investigated using a fibreoptic scope. Fig 33. A. Schematic of LMA ProSeal with gastric tube in situ. B and C. Gastric tube insertion. It is useful to hold the drain tube (B) to facilitate insertion. 26

29 LMA Analysis q Page 27 c. Post-insertion The GT should be suctioned and then either left in situ or removed. An advantage of leaving it in situ is that it can be used to guide the LMA ProSeal back into position if it is displaced 107. In principle, it may also help anchor the distal cuff in the hypopharynx. If left in situ it should be suctioned intermittently. Continual high suction should be avoided as it can cause mucosal trauma and render the GT nonfunctional by blocking the end with mucosal tissue. When the GT is being removed, the LMA ProSeal should be held to prevent dislodgment. Removal can take place before anaesthesia is discontinued, or with the patient awake. Potential advantages of removal under anaesthesia are that: (i) the risk of triggering regurgitation may be reduced; and (ii) the DT is patent in case of regurgitation. Potential advantages of removal awake are: (i) the stomach can be emptied during emergence; and (ii) oropharyngeal secretions can be cleared if suction is applied during simultaneous LMA ProSeal and GT removal. Suction should never be applied directly to the DT as this will result in collapse of the tube and it will become nonfunctional, as if folded over. IX. Maintenance phase The maintenance phase is similar to the LMA Classic, but the LMA ProSeal offers greater scope for ventilation [see section V,B], physiological monitoring and reducing the risk of aspiration/gastric insufflation. The improved ventilatory capability means that minute volume can be better maintained during reductions in pulmonary compliance and volume controlled ventilation is more appropriate. The incidence of problems appears to be similar to the LMA Classic 25,27,50. One group reported that the LMA ProSeal and LMA Classic were similarly effective for PPV in obese patients 29 [see section XIV]. Another reported that 1% of LMA ProSeal failures occur during the maintenance phase 25. Yet another reported that there are fewer ventilatory problems with the LMA ProSeal than the LT 39. Tidal volumes are higher for the LMA ProSeal than the standard LT in spontaneously breathing patients 108. In a 2003 study of 52 adults, Carstensen et al 74 found that the LMA ProSeal and the laryngeal tube suction (LTS ) are equally effective ventilatory devices. There have been 4 reports (5 cases) of regurgitation without aspiration during maintenance 4,6,7,59 [see section V,C]. There is 1 report of the successful use of the LMA ProSeal in prolonged middle ear surgery 16 [see section III,C]. Prompted by 2 cases of oesophageal aspiration of air during partially obstructed spontaneous breathing 49, Brain 95 has suggested that PPV is preferable to spontaneous breathing; however, the author considers it suitable for both. There is 1 case report where the LMA ProSeal was successfully used for postoperative respiratory support lasting 8 hours 109 [see section XII]. X. Emergence phase The emergence phase is similar to the LMA Classic. There are only 3 anecdotal reports 58,62,63 and 7 studies 25,39,50,51,108,110,111 providing relevant information. The anecdotal reports describe regurgitation without aspiration during emergence 58,62,63. One study shows that emergence characteristics are similar to the LMA Classic 25, 2 show that they are similar to the LT 39,108 [see section XVIII,A], and 2 that they are better than the TT 50,51 [see section XVIII,E]. There is a descriptive study looking at exchanging the TT for the LMA ProSeal to facilitate a smooth emergence and a study comparing emergence characteristics after maintenance with propofol, sevoflurane or isoflurane. 1. TT/LMA exchange. In a 2003 brief report, Brimacombe et al described the successful use of the LMA ProSeal for TT/LMA exchange in 18 patients, mostly after suspension laryngoscopy or thyroid surgery, without problems 111. The technique involves insertion of the LMA ProSeal using the GEB technique (to ensure correct placement) and emptying the stomach with a GT before tracheal extubation (to reduce the risk of aspiration). The advantages of the LMA ProSeal are easy access to the stomach and improved ventilatory capability; a disadvantage is that a smaller fibreoptic scope must be used if laryngoscopy is required. 2. Propofol vs volatile. In a 2003 study of 60 adults, Keller et al 110 found that pressure support ventilation is roughly 10% less effective and emergence times are roughly 25% longer with propofol 6 mg/kg/h for maintenance than sevoflurane 2% or isoflurane 1.1%. However, these differences are of doubtful clinical importance. 27

30 LMA Analysis q Page 28 XI. Resuscitation There are no reports of the LMA ProSeal being used for resuscitation, but the improved seal, the potential to protect against regurgitation, easy GT insertion, the option of finger-free insertion and using the GEB-guided technique offers advantages over the LMA Classic and LMA Fastrach. Potential limitations of the LMA ProSeal for resuscitation are that it is more complex to understand, more difficult to insert (digital and IT techniques) and that is must be perfectly positioned to provide most of these advantages. The potential advantages over the LMA Classic are that: (i) it facilitates high airway pressure ventilation; (ii) it provides better protection against regurgitation and gastric insufflation; (iii) it facilitates GT placement; and (iv) insertion is conceptually simple when the IT and GEB is used. There is one manikin study showing that the LMA ProSeal is a more effective ventilatory device than the LMA Classic and LMA Unique, but is a similarly effective ventilatory device to the LMA Fastrach 112 [see section XVIII,D]. There is one clinical study showing that insertion success rates and times are similar for the LMA ProSeal and LMA Classic in anaesthetised patients by naive users 92. Coulson et al 92, in a 2003 crossover study of 60 anaesthetised, paralysed adults by post-anaesthesia care unit nurses following manikinonly training, found that the insertion success rates and times were similar for the LMA ProSeal (90%, 43 s) and LMA Classic (88%, 39 s). XII. Intensive Care The routine use of the LMA Classic in the intensive care unit (ICU) is restricted because high airway pressures cannot be reliably generated, and the lungs cannot be reliably protected from regurgitated gastric contents. The LMA ProSeal has the potential to extend the role of the LMA in ICU as it: (i) facilitates high airway pressure ventilation 24 ; (ii) provides better protection from regurgitation 71,58 ; and (iii) has lower mucosal pressures for a given seal pressure 18 ; however, considerable work is required before it could be considered as an alternative to tracheal intubation. Firstly, studies are required to determine the effects of long term placement of the LMA ProSeal on the pharyngeal mucosa. Currently, there is evidence from anaesthetised, healthy patients that mucosal pressures are low 18 and the incidence of postoperative sore throat is similar to the LMA Classic 25 ; however, a study of 10 ferrets anaesthetised for hours, revealed that the LMA can cause significant upper airway morbidity 113. Secondly, the reliability of the PLMA to protect the patient from aspiration needs to be verified. Currently, this has only be demonstrated in cadavers 71 and anecdotally [see section V,C]. Thirdly, the positional stability of the LMA ProSeal in the ICU setting needs to be established. Currently, this has only been demonstrated in anaesthetised patients 23. In the author s view, the LMA ProSeal will not replace the TT for the majority of ICU patients, but it may become an alternative for short admissions and in specific situations where tracheal intubation is particularly problematic. There are three case reports (percutaneous tracheostomy, postoperative respiratory support and airway rescue) and one study (percutaneous tracheostomy) where the LMA ProSeal has been used in ICU. 1. Case reports. In 2002 Cook and Nolan 56 reported regurgitation without aspiration in an ICU patient undergoing percutaneous tracheostomy with the LMA ProSeal. The lack of aspiration was confirmed by direct vision during the regurgitation event. In 2003, Keller et al 109 reported the successful use of the LMA ProSeal for failed obstetric intubation and postoperative respiratory support in a patient with HELLP syndrome. Both LG-TI and FM ventilation failed with or without cricoid pressure. After surgery was complete, the patient was transferred to the ICU where she was sedated with propofol and ventilated via the LMA ProSeal for 8 hours until the platelet count had risen and she was haemodynamically stable. Weaning and LMA ProSeal removal took 30 min and was uneventful. Nixon et al 75, in 2003, reported the successful use of the LMA ProSeal for airway rescue in a 41-yr-old septic patient who could be neither intubated nor FM ventilated after accidental displacement of an airway exchange catheter while swapping TTs. LG-TI failed, in part, due to bleeding and oedema, and in part due to the high anterior larynx. 2. Study. In 2003 Craven et al 114 reported the successful use of the LMA ProSeal for fibreopticguided, percutaneous tracheostomy in 100% (23/23) of ICU patients. In all patients, bronchoscopy through the LMA ProSeal provided a clear view of the cords and trachea and there was no laryngeal or tracheal soiling at any stage of the procedure. The mean peak inspiratory pressure was 25±4 cm H2O and in only one patient was there a leak in excess of 100 ml. 28

31 LMA Analysis q Page 29 XIII. Difficult airway There is no published data about LMA ProSeal insertion with cricoid pressure applied or with a stereotactic frame / neck collar, but there is one study comparing insertion with the LMA Classic in the neutral position. Asai et al 93, in a 2002 crossover study of 20 adults, found that the first-time (60% vs 80%) and overall (100% vs 75%) success rate for the LMA ProSeal (using the IT) was higher than the LMA Classic with manual-in-line stabilisation applied. In addition, OLP was higher for the LMA ProSeal by 6cm H2O. Insertion in the neutral position should be easy, as the IT can be made to adopt a similar curve to the LMA Fastrach. In principle, cricoid pressure might interfere with insertion more than the LMA Classic, as the distal cuff must sit behind the cricoid cartilage to function. However, once in position, cricoid pressure need not be maintained, as the DT should prevent aspiration and gastric insufflation. Insertion with a stereotactic frame / neck collar should be similar to the LMA Classic, but is probably best performed without the IT to increase manoeuvrability. Insertion success appears to be independent of Mallampati and/or Cormack and Lehane scoring 26. There are 6 case reports 89 and a small case series 26 where the LMA ProSeal has been used in the difficult airway. 1. Case reports. It has been used: (i) for awake fibreoptic-guided insertion in a male with known difficult airway and chronic asthma for a laparoscopic cholecystectomy; (ii) as a ventilatory device in an adult with Rubenstein-Taybi syndrome 115 [see annotated ref]; (iii) as a ventilatory device in an obstetric patient with HELLP syndrome 109 [see section XII]; (iv) as a ventilatory device and for fibreoptic-guided tracheal intubation in a septic adult with bleeding, oedema and high anterior larynx 75 [see section XII]; (v) as a ventilatory device in an obstetric patient at weeks gestation for electroconvulsive therapy 116 [see annotated ref]; and (vi) as a ventilatory device to decompress the stomach after failed intubation and difficult FM ventilation, but successful laryngeal mask ventilation 117 [see annotated ref]. 2. Study. Keller et al 26, in a 2002 study of 60 grossly or morbidly obese adults, found that there were no episodes of hypoxia and only one patient developed hypercarbia when the LMA ProSeal was used as a temporary airway prior to tracheal intubation. Tracheal intubation was subsequently difficult, but possible (required a GEB) in 9/60 and failed in 2/60. In all these patients, the LMA ProSeal was successfully inserted and provided effective ventilation. XIV. Paediatrics The smallest LMA ProSeal currently available is the size 1.5 [see section III]. There is one study. Lopez-Gil and Brimacombe 15, in a 2004 study of 40 children with the size 2 (weighing kg), and 40 children with the size 3 (weighing >25-50 kg), found that the LMA ProSeal is an effective airway device and isolates the glottis from the oesophagus when correctly positioned. Despite the lack of a dorsal cuff, the performance of the size 2 was similar to the size 3 LMA ProSeal in the age groups tested. XV. Coexisting diseases The LMA ProSeal is suitable for patients with a similar range of coexisting diseases to the LMA Classic, but the improved seal allows its use in patients with diseases causing a reduction in pulmonary compliance and the DT allows its use in patients with an increased risk of regurgitation. It has been used in the following conditions: 1. Myasthenia gravis. Gardner and Evans 118, in 2002, reported the successful use of the LMA ProSeal in a patient with myasthenia gravis for a mastectomy to facilitate PPV without muscle relaxation. 2. Obesity. It has been used in obese patients: (i) as a temporary airway prior to tracheal intubation 26 [see section XIII]; (ii) for gynaecological laparoscopy 50 [see section XVIII,E]; and (iii) for laparoscopic cholecystectomy 51 [see section XVIII,E]. There is one study comparing the LMA Classic and LMA ProSeal in obese patients. Natalini et al 29, in a 2003 study of 60 obese patients (BMI > 30 kg/m 2 ) ventilated at 7 ml/kg tidal volume with 10 cm H2O positive end expiratory pressure and managed with the LMA Classic or LMA ProSeal, found that: (i) leak fraction was similar (LMA Classic, 6.1%; LMA ProSeal 6.4%); (ii) there were no problems with ventilation; (iii) intracuff pressure was higher for the LMA Classic ; and (iv) the incidence of sore throat was similar. The authors noted that the DT was not patent in 10% (3/30), presumably due to the foldover malposition. 29

32 LMA Analysis q Page HELLP syndrome. It has been used in a difficult airway patient with HELLP syndrome 109 [see section XIII]. 4. Tracheal narrowing and chronic obstructive pulmonary disease. Dalgleigh and Bromilow 119,in 2003, described the successful use of the LMA for an elderly patient with tracheal narrowing from a mediastinal tumour and chronic obstructive pulmonary disease for an emergency laparotomy after a thoracic epidural failed. XVI. Surgery The LMA ProSeal extends the range of surgical procedures for which LMA devices can be used, further encroaching into the domain of the TT. It is more appropriate than the LMA Classic for surgical procedures where a better seal is required, or where there is a risk of regurgitation during the procedure (arguably all patients). The LMA ProSeal is more appropriate than the LMA Classic for prolonged procedures. The LMA ProSeal, like the LMA Classic, can be used for most head, neck and ENT procedures, but the tube is too rigid for some oropharyngeal procedures, the cuff perhaps too large for some pharyngeal procedures, and the parallel tubes not designed for the Boyle-Davis tonsillar gag. It has been used for gynaecological 25,50, orthopaedic 25, urological 25, plastic 25,107 and laparoscopic surgery 47,51, and electroconvulsive therapy 116. There are three reports of its successful use for fibreoptic-guided percutaneous tracheostomy 56,96,120.In addition, the author has used it extensively for intraabdominal, thyroid, ear (Figure 35) and nose surgery (Figure 36), neck surgery (Figures 37,38) and, occasionally, for oropharyngeal surgery, and in the lateral position (Figure 39A,B), prone position (Figure 40), and beach chair positions. There are 3 studies where it has been used for specific surgical procedures: 2 for gynaecological laparoscopy (Figure 41) 50,122 and 2 for laparoscopic cholecystectomy 47,50 (Figure 42). 1. Gynaecological laparoscopy. Maltby et al 50, in a 2002 study of 209 females for gynaecological laparoscopy, found that the LMA ProSeal, LMA Classic and TT provided equally effective ventilation without clinically important gastric insufflation in nonobese and obese patients. One group reported that the LMA ProSeal and LTS are equally effective ventilatory devices for gynaecological laparoscopy with a similar incidence of airway morbidity 122 [see section XVIII,B] Laparoscopic cholecystectomy. Lu et al 47, in a 2002 study of 80 adults, found that the LMA ProSeal and LMA Classic provided adequate ventilation before carboperitoneum, but ventilation was inadequate or failed after carboperitoneum in 20% with LMA Classic and none with the LMA ProSeal. One group found that the LMA ProSeal and TT provided equally effective ventilation without clinically important gastric insufflation in nonobese patients, but the LMA ProSeal failed in 12% of obese patients (BMI >30 kg/m2) because of respiratory obstruction or air leak 51 [see section XVIII,E]. Fig 34. A morbidly obese patient (BMI, 51 kg/m 2 ) for a lower limb procedure. The patient had reflux twice per month. The LMA ProSeal was easily inserted and tidal volumes in excess of 1.4L were achieved with peak airway pressures of 35 cm H2O. There were no oropharyngeal or oesophageal air leaks.

33 LMA Analysis q Page 31 Fig 35. Major ear surgery with the LMA ProSeal. Note the use of strongly adhesive tape to prevent displacement. The LMA ProSeal is preferable to the LMA Classic as the procedure is prolonged and positive pressure ventilation required. Fig 38. The use of the LMA ProSeal with the head rotated for removal of a parotid tumour (arrow). A catheter mount (CM) has been used to allow more room for attachment of the anaesthesia breathing system. Fig 36. Nasal surgery with the LMA ProSeal. Note that the airway and drain tubes are taped firmly over the chin to avoid interference with the surgical field. Fig 39. The use of the LMA ProSeal in a patient in the lateral position for total hip replacement. The views are from the side (left) and above (right). The anaesthesia breathing system has been positioned so that the proximal airway tube is aligned slightly inferiorly (white line) to maximise the stability of the LMA ProSeal in the pharynx (A). Strongly adhesive tape (S) has been used to minimise the risk of displacement. Moderately adhesive tape (M) has been used to fix the anaesthesia breathing system to the table. The temperature probe (T) is inserted into the nose as the orogastric tube (OG) occupies the drain tube. Fig 37. A 50-yr-old female with a post-operative neck haematoma (arrow) causing mild stridor. The patient refused an awake intubation. The LMA ProSeal was successfully inserted at the first attempt. 31

34 LMA Analysis q Page 32 Fig 40. The use of the LMA ProSeal in the prone position for removal of skin lesions from upper back. A catheter mount (CM) has been used to allow more room for attachment of the anaesthesia breathing system. Strongly adhesive tape (S) has been used to minimise the risk of displacement. The orogastric tube (OG) not only facilitates removal of gas and fluid but can also function as a guide to reinsertion in the unlikely event of displacement. Fig 41. Gynaecological laparoscopy with the LMA ProSeal. Fig 42. The use of the LMA for laparoscopic cholecystectomy. A catheter mount (CM) is used to keep the anaesthesia breathing system out of the surgical field. The gastric tube (GT) is on free drainage. T=temperature probe. XVII. Problems Problems associated with use of the LMA ProSeal are generally similar to the LMA Classic, but their frequency and severity may differ slightly, and there are some which are unique to LMA ProSeal. There is some relevant information about airway morbidity and trauma, but there are no reports of co-incidental problems or disease transmission. There is one report of a device-related problem. A. Airway morbidity and trauma Mucosal pressures are similar to the LMA Classic for a given cuff volume, but are lower for a given seal 18.In principle, the LMA ProSeal might have lower airway morbidity than the LMA Classic ; however, insertion is more difficult and might counteract the beneficial effects of reduced mucosal pressures. There are 4 studies providing information about postoperative airway morbidity: 2 descriptive 40,41 and 2 comparative 25,39. The mean (range) incidence of sore throat is 17% (12-23) [106/607] 25,39-41, of dysphagia is 11% (9-13) [40/352] 25,39,40, of dysarthria is 2% (1-5) [8/352] 25,39,40,of neck ache is 3% (2-3) [7/252] 25,39, and of jaw ache is 2% (2-3) [6/252] 25,39. Over 80% of symptoms were mild and less than 2% were severe. The mean (range) incidence of blood staining is 12% (3-18) [41/352] 25,39,40. 32