Bonfils semirigid endoscope for guidance during percutaneous tracheostomy

Transcription

1 Anaesthesia, 2006, 61, pages doi: /j x APPARATUS Bonfils semirigid endoscope for guidance during percutaneous tracheostomy U. Buehner, 1 J. Oram, 1 S. Elliot, 2 A. Mallick 3 and A. Bodenham 3 1 Specialist Registrar, 2 Research Nurse, 3 Consultant in Anaesthesia and Intensive Care, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK Summary We report on the use of the Bonfils semirigid scope for endoscopic guidance during percutaneous dilational tracheostomy. Forty patients requiring percutaneous dilational tracheostomy on the General or Neurosurgical Intensive Care Unit were enrolled in this study. We used the 45 degree curved distal tip scope in the first 15 patients, evaluating its ease of use, optical quality of focus and image resolution as well as light intensity on a 10-point scale. We evaluated straight and curved versions of it in another 15 and 10 patients, respectively. We examined the impact on ventilation and cardiovascular parameters. In all patients (n ¼ 40) visualisation of the procedure was satisfactory. There were no clinically significant changes in ventilatory or cardiovascular parameters. The image quality for most patients received a score of The Bonfils scope provides a practical alternative to flexible bronchoscopes in this setting.... Correspondence to: Dr A. Bodenham andy.bodenham@leedsth.nhs.uk Accepted: 24 March 2006 Endoscopic guidance during percutaneous dilational tracheostomy (PDT) is increasingly used to visualise needle and guidewire placement, dilation of the stoma and tracheostomy tube placement. Several studies have shown a reduction in the complication rate of PDT, e.g. posterior tracheal wall damage, false passage, pneumothorax and subcutaneous emphysema [1 6]. A number of different techniques for endoscopy have been described, including flexible fibreoptic scopes and the use of rigid bronchoscopes [7] or laryngoscopes. A recognised problem remains the associated relative hypercarbia secondary to intraluminal obstruction by dilators and bronchoscope, leading to iatrogenic hypoventilation [8 11]. It has therefore been recommended to use the smallest bronchoscope available and to minimise suction during bronchoscopy as well as the length of time the bronchoscope is in the tracheal tube [10]. The greatest experience has been gathered with the use of flexible bronchoscopes; most units, however, will have experienced repeated expensive needle damage to their scopes. Over 20 years ago, Pierre Bonfils [12] designed an angulated scope for ear, nose and throat (ENT) use, which in recent years was rediscovered by Christian Rudolph (Leipzig) [13] as an aid to tracheal intubation in difficult airways. It has been commercially available since 1996 (Karl Storz Endoscopy Ltd, Tuttlingen, Germany). The company can adapt the shape of the scope according to user requirements at the time of manufacture. The Bonfils scope (Fig. 1) is a 40 cm long semirigid optical stylet with an external diameter of 5 mm and an anterior tip curvature of 45. Its fibreoptic bundle is encased in a stainless steel tube and attached to an eyepiece and a light source. As an aid to intubation, the tracheal tube is loaded on to the shaft of the device, which is then advanced through the vocal cords and the tracheal tube rail-roaded into the trachea [14 16]. We explored the use of this device for visualisation of the trachea during PDT in anticipation that it could provide adequate endoscopy without risk of damage from needle puncture. The risk of accidental extubation with loss of the airway would potentially be reduced by the scope acting as intubation stylet. Methods The study was approved by the local Ethics Committee for the use of the Bonfils scope and modifications Journal compilation Ó 2006 The Association of Anaesthetists of Great Britain and Ireland 665

2 U. Buehner et al. Æ Bonfils semirigid endoscope Anaesthesia, 2006, 61, pages Figure 1 Original Bonfils Scope. Figure 2 Modified Bonfils Scopes (upper image straight, lower image gentle curve). (straight curved) during PDT on Intensive Care Units (ICU). Forty ICU patients, requiring percutaneous tracheostomy, were recruited over a period of 2 years. Informed assent was taken from the next of kin, explaining the procedure, benefits and risks of both endoscopy and tracheostomy. All patients were anaesthetised with propofol and alfentanil infusions, and were paralysed with cis-atracurium. They were ventilated with 100% oxygen for the duration of the procedure. Local anaesthesia was provided with infiltration of lidocaine 1% with epinephrine 1 : All PDTs were performed using either the Ciaglia Blue Rhino TM (Cook Critical Care, Bloomington, IN) or Portex Ultraperc TM (Smith Medical, Hythe, Kent, UK) percutaneous tracheostomy introducer set. Positive pressure ventilation with volume- or pressurecontrolled ventilation was established in all cases. Ventilatory parameters (tidal volume, mean and peak airway pressure, arterial ph, P a O 2, P a CO 2, F i O 2, oxygen saturation and end-tidal carbon dioxide) were measured at two points during the procedure: prior to the tracheostomy and at the time of tracheal dilatation, as indicated by the ventilator monitor and arterial blood gas measurements. Cardiovascular changes were recorded including pulse rate, blood pressure, central venous pressure and vasopressor requirements. The scopes were connected to a camera-monitor display (Olympus OTV-SC Compact Camera System with OTV-S6 Adapter: AR-T12E with 1.2 magnification; Olympus (UK) Ltd, London, UK). They were scored on a number of variables related to the optical quality (focus, image resolution, light intensity) and the ability to follow each step of the procedure on a scale of 1 10 (1 ¼ poor view and 10 ¼ best view). Following initial evaluation of the conventional scope (10331B, 5 mm outside diameter, 40 cm working length with a fixed 45 distal tip curve and no working channel), Storz provided us with two further shapes (PV B) for evaluation: one straight and the other curved similar to the shape of a standard tracheal tube, both with the same dimensions as above but equipped with a working channel of 1.2 mm (Fig. 2). After insertion of the tracheostomy tube, its correct tube placement was verified via the glottic route, as the semirigid scopes preclude a smooth passage through the tracheostomy tube itself. Following decannulation of the tracheostomy tube, the ICU outreach team followed up all patients for at least 7 days. Results A total of 40 ICU patients requiring percutaneous tracheostomy were enrolled into the study. The patient demographics are displayed in Table 1. In 70% of patients, PDT was performed between 5 and 10 days after tracheal intubation. A quarter of patients 666 Journal compilation Ó 2006 The Association of Anaesthetists of Great Britain and Ireland

3 Anaesthesia, 2006, 61, pages U. Buehner et al. Æ Bonfils semirigid endoscope Table 1 Patient demographics. n Range Mean SD Age; year Weight; kg Height; cm BMI; kg.m ) Days intubated BMI, body mass index; n, number of patients; SD, standard deviation. received early tracheostomy (day 1 4) compared to only 5% who received it late (> day 10). Calculation of the individual body mass index (BMI) revealed that 31% of patients were overweight (BMI > 25) and 42% were obese (BMI > 30) or morbidly obese (BMI > 35). The time taken from needle puncture of the trachea to insertion of the tracheostomy tube ranged from 4 to 15 min depending on patient characteristics (BMI, other anatomical difficulty) and level of operator experience. In 12 of 40 patients (30%) a tracheal ring fracture occurred during the dilation of the stoma with the single curved dilator. There were no clinically detectable immediate or longer-term sequelae noted. We used the original Bonfils Laryngoscope for the first 15 patients, and the curved and straight version of it in a further 15 and 10 patients, respectively. Collectively, we found the curved scope to be the easiest to insert and pass down the tube with the least distortion of the tube and trachea. The use of the original 45 degree curved distal tip scope required disconnection of the catheter mount from the tracheal tube to allow easier insertion of the distal, acutely angled end-piece of the scope. With the straight and curved scopes we encountered after several optimal uses a problem with the focus and deterioration in image resolution due to a leak around the O-ring. It most likely developed during the sterilisation process, allowing water to enter the lens above the fibre-optic bundle. Subsequently, Karl Storz Endoscopy made a product-wide modification resolving this problem. We experienced difficulty in passing the scopes through the acute angulation of the tracheostomy tubes. The original Bonfils scope can be pushed through, but some force is required. The two modified scopes did not pass easily through tracheostomy tubes, and after initial unsuccessful attempts, this was not evaluated further. In all cases, the shaft of the tracheostomy tube with the inflated cuff beyond could be visualised within the trachea at the end of the procedure via the scope passed through the glottis. Image quality Operators were asked to score the view obtained with the individual scope on a 10-point scale (1 ¼ poor, Table 2 Mean scores of a 10-point quality assessment of the images obtained. Image n Range Mean SD Trachea Needle Dilation Glottis Brightness Focus Resolution n, number of patients; SD, standard deviation. Table 3 Cardiovascular parameters before the procedure and post dilation of tracheal stoma. Mean Pre Post p-value MAP; mmhg HR; beats per min < CVP; mmhg MAP, mean arterial pressure; HR, heart rate; CVP, central venous pressure. 10 ¼ excellent) in relation to image quality and view of the relevant structures during the procedure. The scores showed a similar variation for each of the scopes and were therefore summarised as one group in Table 2. Although the individual scores varied, the use of the scope was only abandoned in three of 40 patients. In two cases, this was due to excessive secretions, and in another case to the primary pathology of pulmonary haemorrhage. Haemodynamic stability There was little intra-patient variation as regards cardiovascular parameters. Clinically, small changes were temporally related to operative events, rather than insertion and manipulation of the scope (Table 3). Ventilatory stability A comparison of the means of arterial ph, P a CO 2 and endtidal carbon dioxide prior to tracheostomy and post dilation was statistically significant but did not equate to clinical significance (Table 4). Table 4 shows decrease in tidal volumes, producing overall a small decrease in ph; in only two patients did this lead to an arterial ph outside the normal range of In one case, the starting ph of 7.33 was already reduced, and in the other the tracheostomy procedure was technically difficult and prolonged. Journal compilation Ó 2006 The Association of Anaesthetists of Great Britain and Ireland 667

4 U. Buehner et al. Æ Bonfils semirigid endoscope Anaesthesia, 2006, 61, pages Table 4 Ventilatory parameters before the procedure and post dilation of tracheal stoma. A clinically significant rise in arterial carbon dioxide up to kpa was found in six patients. For the first five patients of our study, we still used a catheter mount with standard suction cap that led to a large air leak around the rigid scope and therefore impaired ventilation. Another patient was morbidly obese with a BMI of 58, undergoing a technically more challenging tracheostomy, prolonging the procedure to 14 min. The apparent improvement in oxygenation is due to 100% oxygen being used throughout the procedure. There was no significant difference in the 40 patients in the mean airway pressures pretracheostomy and during dilation. Discussion Mean Pre Post p-value Arterial ph P a O 2 F i O 2 ; mmhg < P a CO 2 ; kpa < Peak P AW ;cmh 2 O Tidal volume; ml < P a O 2 F i O 2, arterial partial pressure of oxygen inspired oxygen fraction ratio; P a CO 2, arterial partial pressure of oxygen; Peak P AW, peak airway pressure. The Bonfils scope and the two derived scopes are capable of providing adequate views for the safe conduct of percutaneous tracheostomy. It would be difficult to damage any of the devices with a needle, as can occur with a flexible bronchoscope. Although, objectively, the three scopes did not differ in their visual score rating and measured variables, feedback from the operators unanimously suggested that the scope with the gentle curve was the easiest to use. Ventilation was only slightly reduced once the bronchoscopic connector was modified to avoid an air leak and associated rise in carbon dioxide. This favours its use in neurosurgical or neurological patients who are at risk of secondary brain ischaemia from raised intracranial pressure associated with any significant rise in arterial carbon dioxide. All three scopes are easily assembled and connected to a monitor display. They allow good visualisation of the stepwise PDT procedure. Most of the problems that we initially encountered with the Bonfils scope were easily dealt with by minor adaptations. The bronchoscopic Portex connector, through which the scope was introduced, produced an inadequate seal around the rigid scope due to its small diameter and straight shaft compared with the flexible bronchoscope. The gas leak was aggravated by any radial pressure applied by the rigid body of the scope, which led to distortion of the port aperture and impaired ventilation with resultant small tidal volumes and clinically relevant rises in arterial carbon dioxide. We tried various connector devices the first five times we used the Bonfils scope before settling for a catheter mount with a rubber membrane instead of the suction cap. The membrane required prior piercing with a needle to allow easy insertion of the scope. Any radial movement of the scope could then stretch the small aperture without producing a significant leak. The adaptation of the original scope, exchanging the angulation at the distal end for a gentle curvature throughout its body, made a smooth passage through the tracheal tube possible without disconnection from the ventilator. One of the remaining problems was the lack of a suction channel. Secretions caused problems in two ways: loose, wet secretions often required the removal of the scope to clean the distal fibre-optic and perform suction through the tracheal tube with a suction catheter. We also faced problems with dried secretions lining the inside of the tracheal tube. The dried secretions would peel off as the leading edge of the scope was advanced through the tube. In this situation, re-intubation with a new tube was beneficial. It was rare for the secretions to re-accumulate as long as they had been adequately cleared at the start of the procedure. Both modifications of the Bonfils scope, the straight and the curved, had a 1.2 mm working channel, designed to keep the optics clear when high levels of secretions are present. A small bolus of saline or air was often enough to de-fog the optic and clear the view, provided the secretions were loose. Both scopes provided equally good views of the tracheostomy procedure. The tracheal tube-like curvature gives the curved scope a practical advantage in its ease of use. Modifications to the shape of the Bonfils scope need to be performed in the factory to avoid kinking the metal sleeve of the scope. Karl Storz Endoscopy recommends that clinicians discuss any desired modifications of the semirigid scopes with the manufacturer to avoid any deterioration in the scope function and potential harm to patients. Other companies market more malleable scopes that allow clinicians to modify the shape for individual patients. Karl Storz Endoscopy have modified the scopes that we used further, converting the focus ring into a fixed focal length, thereby increasing the robustness of the scope without affecting image quality significantly. The company have recently launched a 3.5 mm Bonfils scope 668 Journal compilation Ó 2006 The Association of Anaesthetists of Great Britain and Ireland

5 Anaesthesia, 2006, 61, pages U. Buehner et al. Æ Bonfils semirigid endoscope Table 5 Comparison of five commercially available optical stylets. Stylet Diameter Fibre type Pixel count Angle of view Viewing element Light-source Flexibility & radius of curvature Bonfils [14 17] 5 mm 40 cm Glass Eyepiece Storz fibre-optic connector Rigid 45 anterior tip curvature Fibre-lightview Shuttle [17] 3.5 mm 33.5 cm Glass Eyepiece Battery handle Malleable to 90 Shikani optical stylet (SOS) [18 21] 5 mm 27 cm Glass Eyepiece Fibre-optic connector Malleable to 90 J-shaped Video-optical intubation stylet 3.8 mm 40 cm Glass Chargedcoupled Custom Malleable to 90 (VOIS) [22 26] device Fibre-optic stylet scope (FSS) [27, 28] 7 mm Plastic Eyepiece Battery handle 75 anterior tip flexibility with even greater image resolution. If suitable and robust enough, it should not compromise ventilation during the PDT. In our unit, we reserve these scopes for percutaneous tracheostomy to avoid the risk of expensive needle damage. Difficulties may be encountered on attempting to pass the scopes through tracheostomy tubes, due to the acute angulation of the tube, but tube position within the trachea can be verified from above via the larynx. We are aware of other scopes of a similar nature, and more than 10 optical stylet devices have been introduced since 1995, of which five are still commercially available (Table 5). Potential advantages of optical stylets include their intuitive handling, requiring no new skills; a flexible tip may allow adjustment of viewing angle. They may function as stylet, endoscope or lightwand. Compared to flexible fibre-optics, these semirigid scopes are cheaper to purchase and easier to clean and sterilise. Their nominal diameter is fixed, therefore providing predictable ventilation throughout the PDT procedure, whereas the diameter of the flexible fibre-optics may change due to buckling or wrinkling of the outer sheath distally, especially in older scopes. In conclusion, the Bonfils scopes provide a useful and safe alternative to flexible fibreoptic bronchoscopy during percutaneous tracheostomy. Newer derivatives of the original scope may make it easier to use. They provide good optical views of the tracheostomy procedure from within the trachea, with the advantage of a robust metal cased scope, resistant to accidental needle damage. Acknowledgements We thank Karl Storz Endoscopy for their technical support and the provision of the Bonfils scope and the two modifications. We are grateful to colleagues for scoring the performance of the scopes and to the ICU staff for their co-operation. The authors declare no conflict of interest relating to the publication of this study. References 1 Beiderlinden M, Walz KM, Sander A, et al. Complications of bronchoscopically guided PDT. beyond the learning curve. Intensive Care Medicine 2002; 28: Hinerman R, Alvarez F, Keller CA. Outcome of bedside percutaneous tracheostomy with bronchoscopic guidance. Intensive Care Medicine 2000; 26: Sirak P. Percutaneous tracheostomy. Critical Care 1999; 3: Fernandez L, Norwood S, Roettger R, et al. Bedside percutaneous tracheostomy with bronchoscopic guidance in critically ill patients. Archives of Surgery 1996; 131: Barba CA, Angood PB, Kauder DR, et al. Bronchoscopic guidance makes percutaneous tracheostomy a safe, costeffective, and easy-to-teach procedure. Surgery 1995; 118: Winkler WB, Karnik R, Seelmann O, et al. Bedside percutaneous dilatational trachesotomy with endoscopic guidance: experience with 71 ICU patients. Intensive Care Medicine 1994; 20: Grigo AS, Hall NDP, Crerar-Gilbert AJ, et al. Rigid bronchoscopy-guided percutaneous tracheostomy. British Journal of Anaesthesia 2005; 95: Ferraro F, Capasso A, Troise E, et al. Assessment of ventilation during the performance of elective endoscopic-guided percutaneous tracheostomy. Chest 2004; 126: Marelli D, Paul A, Manolidis S, et al. Endoscopic guided percutaneous trachesotomy: early results of a consecutive trial. Journal of Trauma 1990; 30: Reilly PM, Sing RF, Giberson FA, et al. Hypercarbia during tracheostomy: a comparison of percutaneous endoscopic, percutaneous Doppler, and standard surgical tracheostomy. Intensive Care Medicine 1997; 23: Reilly PM, Anderson III, Sing RF, et al. Occult hypercarbia: an unrecognised phenomenon during percutaneous endoscopic tracheostomy. Chest 1995; 107: Bonfils P. Fibreoptic intubation. Intensivbehandlung 1983; 8: Journal compilation Ó 2006 The Association of Anaesthetists of Great Britain and Ireland 669

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