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1 MINERVA ANESTESIOLOGICA EDIZIONI MINERVA MEDICA This provisional PDF corresponds to the article as it appeared upon acceptance. A copyedited and fully formatted version will be made available soon. The final version may contain major or minor changes. Indirect videolaryngoscopy with C-MAC D-Blade and GlideScope: A randomized, controlled comparison in patients with suspected difficult airways G. Serocki, T. Neumann, E. Scharf, V. Dörges, E. Cavus Minerva Anestesiol October 02. [Epub ahead of print] Minerva Anestesiologica A Journal on Anesthesiology, Resuscitation, Analgesia and Intensive Care Official Journal of the Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care pissn eissn Article type : Original Article The online version of this article is located at Subscription: Information about subscribing to Minerva Medica journals is online at: Reprints and permissions: For information about reprints and permissions send an to: journals.dept@minervamedica.it - journals2.dept@minervamedica.it journals6.dept@minervamedica.it COPYRIGHT 2012 EDIZIONI MINERVA MEDICA

2 Indirect videolaryngoscopy with C-MAC D-Blade and GlideScope: A randomized, controlled comparison in patients with suspected difficult airways. G. Serocki 1, T. Neumann 2, E. Scharf 1, V. Dörges 3, E. Cavus 1 1 Consultant, Anaesthesiologist, 2 Resident, 3 Professor of Anaesthesiology All authors are staff members of the Department of Anaesthesiology and Intensive Care Medicine, University-Hospital Schleswig-Holstein UKSH, Campus Kiel, Chair: Prof. Dr. med. M. Steinfath, Schwanenweg 21, Kiel, Germany; phone: , fax: Address for correspondence: Dr. Götz Serocki, MD Department of Anaesthesiology and Intensive Care Medicine, University-Hospital Schleswig-Holstein UKSH, Campus Kiel, Schwanenweg 21, Kiel, Germany; phone: , fax: ; serocki@anaesthesie.uni-kiel.de Co-Authors Tobias Neumann, MD: Dr. Edwin Scharf, MD: PD Dr. Erol Cavus, MD: Prof. Dr. Volker Doerges, MD: t.neumann@anaesthesie.uni-kiel.de scharf@anaesthesie.uni-kiel.de cavus@anaesthesie.uni-kiel.de doerges@anaesthesie.uni-kiel.de

3 Abstract Background: Recently, indirect videolaryngoscopes have become increasingly important devices in difficult airway management. The aim of the present study was to investigate laryngoscopic view and intubation success using the new C-MAC D-Blade in comparison to the established GlideScope videolaryngoscope and conventional direct laryngoscopy in a randomized controlled trial. Methods: Ninety-six adult patients with expected difficult airways undergoing elective ear, nose and throat surgery (ENT) requiring general anaesthesia were investigated. Repeated laryngoscopy was performed using a conventional direct Macintosh laryngoscope (DL), C-MAC D-Blade (DB) and GlideScope (GS) in a randomized sequence before patients were intubated with the last device used. Results: Both videolaryngoscopes showed significantly better C/L (Cormack-Lehane) classes than DL. Insufficient laryngoscopic view, defined as C/L III, was experienced in 18 patients (19.2 %) with DL, in two patients with GS (2.1 %) and in none with DB (0%). Time to best achievable laryngoscopic view did not differ between devices. Intubation time was significantly longer with both videolaryngoscopes (Median [Range] DB: 18 [8-33] s, and GS: 19 [9-34] s) than with DL (11 [5-26] s). However, intubation success was 100 % for both DB and GS, whereas four patients could not be intubated using conventional direct laryngoscopy. Conclusions: Compared to direct Macintosh laryngoscopy, both C-MAC D-Blade and GlideScope comparably resulted in an improved view of the glottic opening with successful tracheal intubation in all patients. Key words laryngoscopy, airway management, endotracheal intubation, laryngoscopes, airway control

4 INTRODUCTION Endotracheal intubation is commonly performed under direct visualization using a conventional Macintosh laryngoscope. The majority of patients can successfully be intubated using this rather simple technique. Nonetheless, a straight line of sight may not be achievable in all patients with the limited direct view angle of approximately Insufficient laryngoscopic view remains a leading reason for difficult intubations, thus considerably contributing to anaesthesia related morbidity and mortality 1-3. In the recent Fourth National Audit Project for mayor complications of airway management in the UK, overall 39 % of the reported events were associated with difficult intubation, failed intubation, or can t intubate, can t ventilate scenarios 4. Over the last decade, videolaryngoscopy has successfully been introduced into routine as well as difficult airway management. The first instruments, featuring Macintosh-like blade forms, were essentially introduced to improve teaching 5, but proved to be helpful when dealing with difficult airways, too. Subsequently, several videolaryngoscopes with a special emphasis on the management of the difficult airway were developed. The GlideScope is an established videolaryngoscope featuring a highly angulated blade form, thus offering an obligate indirect glottic view. It has been investigated extensively by several authors 6-9 during clinical routine. In most cases, it enables laryngoscopic view superior to both conventional direct laryngoscopy and Macintosh videolaryngoscopy in patients with suspected difficult airways 6. The C-MAC videolaryngoscope by Karl Storz was introduced with conventional Macintosh blades in different sizes, appropriate for routine airway management or educational purposes 10. To further improve the potential in the management of the difficult airway, the C-MAC system has recently been complemented with an obligate indirect blade form, the highly angulated D-Blade 11. The purpose of the present randomized controlled trial was to compare the videolaryngoscopes C-MAC D- Blade and GlideScope GVL with conventional direct Macintosh laryngoscopy in patients with expected difficult airways undergoing elective ENT (ear, nose and throat) surgery. Primary end-points were laryngoscopic view, intubation time and success rate.

5 METHODS STUDY DESIGN AND PATIENTS Ninety-six patients scheduled for elective ENT surgery requiring endotracheal intubation according to institutional anaesthesiological management were enrolled in this study. Institutional review board approval and written informed consent were obtained from all patients. All patients included presented with at least one of the following predictors of a difficult airway: Mallampati 12 score 2, reduced mobility of the atlanto-occipital joint ( 15, acc. Bellhouse 13 ), mouth opening (< 4 cm acc. el-ganzouri 14 ) and thyromental distance (< 6 cm acc. Patil 15 ). Exclusion criteria were refusal of participation, patients age < 18 years and ASA-classification > 3, indication for rapid sequence induction, known difficult face mask ventilation and hypopharyngeal or laryngeal tumors with the risk of bleeding or swelling. The investigation was carried out by three board certified anaesthesists (G.S., E.C., E.S.) familiar with all laryngoscopes (> 50 intubations each). LARYNGOSCOPES Direct Laryngoscopy (DL) Direct laryngoscopy was perfomed with a conventional laryngoscope equipped with a battery handle and convertible Macintosh blades (Macintosh Classic, Heine Optotechnik GmbH, Herrsching, Germany) as routinely used in our department (Fig. 1). Macintosh blade size 3 was routinely used for female and male patients, blade 4 was used only for tall individuals. GlideScope (GS) The GlideScope video laryngoscope (Verathon Medical, Bothwell, USA), was the first obligate indirect video laryngoscope commercially available. With an upwards angulation of 60 the blade design differs significantly from Macintosh blades (Fig. 1). The camera pod is located at a marked inflection point from which the distal blade continues straight forward for another 58 mm. The instrument incorporates a CMOS (complementary metal oxide semiconductor) video chip and light-emitting diodes (LEDs) in a medical-grade plastic shell. It is provided in different sizes, Large was used in this study. The laryngoscope is connected to a 7"-LCD-colourmonitor by a cable, supplying power and transmitting video signals. After introduction of the GlideScope into the oral cavity, further advancement of the instrument along the midline towards the plica glosso-epiglottica has to be performed under indirect visual control via monitor. Due to the angulated blade form, the endotracheal tube has to be shaped similarly by the use of a semi-rigid stylet. The tube should be proceeded cautiously until the tip becomes visible on the monitor. After introduction into

6 the glottic opening, the tube should be shifted off the stylet held in position. No preparation routine is required to use the GlideScope. D-Blade for C-MAC videolaryngoscope (DB) The recently introduced D-Blade (Karl Storz GmbH, Tuttlingen, Germany) was essentially designed for the management of the difficult airway. It extends the assortment of different blade forms adaptive for the C-MAC system. The D-Blade shows a pronounced angulation of 40. Like all C-MAC blades, D-Blade incorporates a small CMOS camera chip with an embedded optical lens with an aperture angle of 80, located laterally in the distal third of the steel blade (Fig.1). In contrast to the GlideScope, the D-Blade s camera and light socket is located nearer (40 mm) to the blades tip, which is bended for another 20. A high-power LED serves as light source. The laryngoscopic view is displayed on a portable high-resolution LCD colour monitor. Single pictures or a video stream may be stored on a secure digital (SD-) card using the implemented secure digital slot. The D-Blade is inserted into the oral cavity in the midline and carefully advanced under monitor vision until the tip is positioned at the vallecula, thus enabling vision of the glottic opening. Due to the D-Blade s specific shape a direct laryngoscopic view, as it is possible with the original Macintosh blade forms 3 and 4 for C-MAC videolaryngoscope, is not intended and will actually be impossible in most patients. Therefore, intubation technique is similar to GlideScope and requires the use of a preshaped semi-rigid stylet. No preparation routine is required according to the manufacturer s instructions. STUDY PROTOCOL Standard cardiovascular monitoring devices including ECG (electrocardiogram), non invasive blood pressure, peripheral oxygen saturation and capnography (all S/5 Datex-Ohmeda, Helsinki, Finland) were attached. A firm pillow of appropiate height was used to raise the patients head into an optimized sniffing position. Patients were then preoxygenated via face mask for 3 minutes. General anaesthesia was induced intravenously with 2 mg kg -1 propofol and remifentanil at a rate of 0.3 µg kg -1 min -1 and maintained with 3-5 mg kg -1 h -1 propofol and µg kg -1 min -1 remifentanil, respectively. Before laryngoscopy, patients were paralyzed with 0.6 mg kg -1 rocuronium, and train-of-four stimulation of the ulnaric nerve was used to verify complete neuromuscular blockade (TOF count = 0). Repeated laryngoscopy was then performed in a randomized sequence by opening of a sealed envelope. Cormack-Lehane view (C/L) modified by Yentis and Lee 16 was identified by the investigators. If appropriate, additional external laryngeal manipulation (ELM) was applied to improve laryngoscopic view. For each laryngoscopy, time was measured starting from touching the laryngoscope until achievement of best glottic view. In between laryngoscopies, patients were ventilated by face mask to ensure adequate oxygenation.

7 Intubation was then attempted with the last device used, thus establishing three groups of n = 32 patients for each laryngoscope. The number of intubation attempts and the time needed from touching the endotracheal tube until cuff inflation (intubation time) were documented. Another intubation attempt was defined by complete retraction and reinsertion of the laryngoscope. After three unsuccessful intubation attempts the case was assessed as failed. Also, in case of completely insufficient laryngoscopic view (C/L IV) even with external laryngeal manipulation investigators were allowed to pass on repeated intubation attempts. If intubation was not possible, the airway was managed according to institutional guidelines for the management of the difficult airway. Time measurement did not include failed intubations. Bilateral lung auscultation and capnography verified successful intubation and ventilation. We used standard cuffed ET-Tubes with an inner diameter of 7.0 mm for female and 8.0 mm for male patients. All ET-Tubes were equipped with semi-rigid stylets. The use of GlideScope and C-MAC D-Blade requires a distinctively curved stylet resembling the blade form ( hockey-stick configuration ). For intubations with the conventional direct laryngoscope stylets were bent only moderately. In case of complications such as oxygen desaturation (< 90%) or severe cardiocirculary depression, the protocol was stopped immediately. STATISTICAL ANALYSIS: Statistical analysis was performed using GraphPad Prism software version 5.01 (GraphPad Software Incorp., CA, USA). Significance was tested using non-parametric tests. Friedman test with Dunn`s multiple Comparison Test was used for dependent samples with repeated measurements (laryngoscopic view and time) and Kruskal- Wallis test with Dunn`s multiple Comparison Test for independent samples (comparability of demographics and predictors between groups, intubation attempts and time). For all statistical tests, p < 0.05 was considered significant.

8 RESULTS In total, 96 patients were enrolled in this study. Due to severe problems with face mask ventilation leading to oxygen desaturation of < 90%, the study protocol had to be stopped in one patient (GlideScope group). No adverse effects such as severe oxygen desaturation, severe cardiocirculatory depression or any other adverse effects did occur in any other patient. Therefore, 95 data sets were further evaluated. Except for distribution between the sexes, there were no significant differences between groups regarding demographic data (Table 1) and predictors of a difficult airway (Table 2). There was a high incidence of insufficient glottic view (C/L grade III or IV) with conventional direct laryngoscopy. Even with additional external laryngeal manipulation (ELM) the vocal cords could not be seen (C/L III) in 18 patients (19 %) with the conventional Macintosh laryngoscope and in another 14 individuals (15%) only arytenoids or posterior portion of cords (C/L IIb) were visible (Fig. 2). In contrast, both video laryngoscopes enabled significant better visualisation of the glottic opening compared to direct laryngoscopy (Fig 2, p < 0.05). A C/L view IIb was seen in 92 patients (97 %) when using the GlideScope and in all 95 patients (100%) with the D-Blade (Fig. 2). Compared to the direct laryngoscopic view, the videolaryngoscopic view was improved by two C/L score grades in 34 (36 %) and of more than two grades in 20 (21%) patients with the D-Blade, and in 37 (39%) and 10 (11%) patients with the GlideScope, respectively. No change or worsening of the glottic view was seen in 11 (12%) and 3 (3%) patients with the D-Blade, and in 22 (23%) and one (1%) patient with the GlideScope, respectively. Mean time to best achievable laryngeal view was comparable between all devices. Time to tracheal intubation was significantly faster with conventional direct laryngoscopy than with both videolaryngoscopes (Table 3). Four patients could not successfully be intubated using direct laryngoscopy (success rate 87%). These patients were successfully managed with the D-Blade videolaryngoscope within the first attempt. In contrast, intubation success rate was 100% for both videolaryngoscopes. Three attempts for successful intubation were necessary in one patient with either the D-Blade and the GlideScope, respectively (Table 3).

9 DISCUSSION Videolaryngoscopy was originally introduced to facilitate teaching of novice users 17. The magnified display of the view obtained by the camera on an external monitor enables observance by operator as well as supervisor 5. The first videolaryngoscopes featured Mac-intosh or Miller blade forms, thus offering intubation conditions and technique comparable to conventional direct laryngoscopy 5,17. Therefore, Macintosh videolaryngoscopy may be learned intuitively by operators familiar with the classical technique. Additionally, videolaryngoscopic devices also revealed potential in difficult airway management. With videolaryngoscopy, the operator`s eye is virtually relocated deep into the hypopharynx enabling a lookaround-the-corner. Consequently, obligate indirect video-laryngoscopes with angulated blade forms, such as the GlideScope 18 and the McGrath videolaryngoscope 19, were introduced to improve laryngoscopic view compared to conven-tional direct laryngoscopy. The current study was designed to evaluate the performance of the new indirect videolaryngoscope C-MAC D- Blade in comparison with the GlideScope GVL, since the GlideScope is the most extensively evaluated indirect laryngoscope. It has been demonstrated by several authors that the GlideScope offers superior laryngoscopic views compared to conventional Macintosh laryngoscopes in manikins 20, unselected study groups 18 as well as in patients with simulated 21 or anticipated difficult airways 6,7. The incidence of positive predictors of a difficult airway as well as actually insufficient direct laryngoscopic view (C/L III 19 %) was higher than for unselected groups given in litera-ture 1,2. In the present study, an index was not calculated. However, the study was performed in the ENT Department, and the nature of anaesthesia in ENT surgery per se has a higher incidence of difficult airways that cannot be summed up by index numbers, such as bulk masses, dislocation or narrowing of the glottis. Compared to direct laryngoscopy, our data clearly demonstrate superior laryngoscopic views for both videolaryngoscopes, consistent with previous findings 6,7,9,11. As a trend, a better view was obtained with the C- MAC D-Blade than with the GlideScope. Apparently, the angulated blade forms of both instruments offer an effective and comparable look-around-the corner, thus enabling excellent glottic exposure even in those individuals, in which conventional direct laryngoscopy displays only parts of the glottic opening or even less. Our investigation also quantified the individual extent of glottic view improvement with direct laryngoscopy as reference: the D-Blade most commonly improved glottic view by two grades. Deterioration of glottic view occurred in three patients. Similarly, the GlideScope showed a pronounced ability to enhance glottic view,

10 corresponding to previous findings 8,18. Deterioration using the Glide-Scope also occurred in one patient with easy direct laryngoscopy (C/L I). Improvement of glottic view from C/L class III to class IIb has to be regarded clinically relevant, since it is likely to enhance intubation success and safety. Improvement of glottic view to a sufficient grade (C/L IIb) was obtained in most patients with GS and in all with use of the D-Blade. Therefore, both videolaryngoscopes may be helpful devices when difficult intubation is caused by insufficient laryngoscopic view. The introduction into the mouth and further advancement of both videolaryngoscopes often presented to be more delicate than with the conventional Macintosh laryngoscope, caused by the attached cables and the angulated blade form. However, these difficulties seemed to be compensated by rapid achievement of best glottic exposure with the videoassisted devices resulting in comparable laryngoscopy times for all three laryngopscopes. In contrast, intubation time with both videolaryngoscopes was longer than with direct laryngoscopy. Apparently, intubation under indirect visual control via monitor requires a complex hand-eye-coordination. Since the investigators were familiar with both video-laryngoscopes, there may be only minor potential for reduction of time required for intubation. However, a difference of only a few seconds may well be regarded as irrelevant, considering that intubation success in a reasonable time is more relevant for the patient s safety than the duration of the procedure itself. The difference between failed intubation with direct laryngoscopy compared to both videolaryngoscopes is not significant. This might have been different with a higher number of patients. Nevertheless, both videolaryngoscopes showed no failed cases at all. Intubation difficulties with both indirect videolaryngoscopes were not related to insufficient glottic exposure. This fact indicates that the improved glottic view with indirect video-laryngosopes does not guarantee straightforward intubation success, consistent with previous evaluations of the GlideScope 8,9,18. The specific angulated blade forms of both the C-MAC D-Blade and the GlideScope do not compress the tongue root as much as relatively linear blade forms like Macintosh or Miller. Moreover, they do not align oral, pharyngeal and laryngeal axes to the same degree as the latter. In consequence, the tube s way into the trachea must be angulated as well, so the use of a stylet is mandatory. Oropharyngeal space is restricted and the tube may get caught at the arytenoids or the ventral tracheal wall when proceeding in a relatively steep angle through the glottic opening. If endotracheal tube and tracheal axis do not align, it may be helpful to rotate the tube and approach not in the midline, but more from the lateral right side. A specific injury potential reported for the use of the GlideScope 23 may also apply to other indirect videolaryngoscopes, including the D-Blade. Therefore, indirect videolaryngoscopes may not be recommendable as first choice for routine intubation but for anticipated as well as unanticipated difficult airway management. For the latter, videolaryngoscopy apparently can be a very helpful technique if restricted laryngoscopic view is

11 the problem. It should be noted, that indirect videolaryngoscopy may not necessarily be beneficial in difficult intubation due to glottic or subglottic pathologies like tumors, abscesses or bleedings. Compared to the incidence of unsuccessful intubation given in other studies 3,4,24,25, intubation failure rate for direct laryngoscopy in our study presents rather high. This may be explained by the clinical setting in ENT surgery as well as by the study protocol excluding blind or bougie-guided techniques and, foremost, by the limitation of three intubation attempts. Routine use of videolaryngoscopy may not become standard in many institutions, because conventional direct laryngoscopy serves well in most cases at reasonable costs and hygienic preparation processes. In certain surgical disciplines like ENT (ear, nose and throat) or CMF (cranio-maxillofacial) surgery the incidence of difficult laryngoscopy and intubation is higher than the average 26, regularly requiring alternative intubation devices. For the anticipated or known difficult airway, flexible fibreoptic intubation under spontaneous breathing still remains the gold standard. In cases of unanticipated difficult laryngoscopy and intubation, fibreoptic intubation may be less helpful due to extended time required for equipment preparation and the handling procedure itself, as well as its vulnerability to secretion and bleeding. Therefore, it may be helpful to have a versatile airway management system for direct and indirect laryngoscopy with a Macintosh blade and, moreover, the possibility for an immediate change to another blade form with minimal time loss. This important characteristic distinguishes the D-Blade from other self-contained indirect videolaryngoscopes such as the GlideScope or the McGrath videolaryngoscope. LIMITATIONS In the present study, an index was not calculated. However, the study was performed in the ENT Department, and the nature of anaesthesia in ENT surgery per se has a higher incidence of difficult airways that cannot be summed up by index numbers, such as bulk masses, dislocation or narrowing of the glottis. The investigation was carried out by different anaesthetists, thus allowing for bias. However, all anaesthesists performing laryngoscopy never took part in the development of the laryngoscopes investigated. Volker Doerges, who was essentially involved in the developement of the D-Blade, did not perform laryngoscopy and intubation. Furthermore, the study was not blinded, a common problem in evaluating airway devices, thus exposing it to potential observer bias. However, this design has the advantage of comparability between the views obtained from one patient. Since at least videolaryngoscopic views could be witnessed by the nursing staff to control observer bias, main findings of this study have to be considered reliable. In conclusion, both videolaryngoscopes C-MAC D-Blade and GlideScope comparably enable excellent visualisation of the glottic opening resulting in high intubation success rates. Both videolaryngoscopes may

12 therefore be useful alternatives for the management of the difficult airway. Further testing in clinical settings is warranted to evaluate the D-Blade for difficult or failed conventional intubation. Key Messages: - Compared to direct laryngoscopy, both videolaryngoscopes C-MAC D-Blade and GlideScope provided superior laryngoscopic views. - The angulated blade forms of both videolaryngoscopes offer an effective and comparable look-around-the corner, thus enabling excellent glottic exposure even in those individuals, in which conventional direct laryngoscopy displays only parts of the glottic opening - Intubation failed in 4 patients after direct laryngoscopy but was successful in 100% patients with both videolaryngoscopes. - Even with trained operators, intubation time with both videolaryngoscopes was longer than with direct laryngoscopy. ACKNOWLEDGEMENTS: We are grateful to Karl Storz GmbH, Tuttlingen, Germany and Verathon Medical, Rennerod, Germany for supplying the videolaryngoscopes and we are much obliged to the involved nursing staff of our Department for their dedicated assistance. COMPETING INTERESTS Funding was restricted to institutional and departmental sources. The University Hospital Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, or any of its employees, recieve no compensation for this work. However, Volker Doerges is a member of the Karl Storz advisory board, was involved in the development of C-MAC D-Blade and receives grant support from Karl Storz, Tuttlingen, Germany, for studies related to airway management.

13 References 1. Williams K, Carli F, Cormack R. Unexpected, difficult laryngoscopy: a prospective survey in routine general surgery. Br J Anaesth. 1991;66: Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia. 1984;39: Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth. 1994;41: Cook TM, Woodall N, Harper J, Benger J. Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2: intensive care and emergency departments. Br J Anaesth. 2011; 106(5): Kaplan MB, Ward D, Hagberg CA, Berci G, Hagiike M. Seeing is believing: the importance of video laryngoscopy in teaching and in managing the difficult airway. Surg Endosc. 2006;20(Suppl.2): Serocki G, Bein B, Scholz J, Dorges V. Management of the predicted difficult airway: a comparison of conventional blade laryngoscopy with video-assisted blade laryngo-scopy and the GlideScope. Eur J Anaesthesiol. 2010;27: Stroumpoulis K, Pagoulatou A, Violari M, et al. Videolaryngoscopy in the management of the difficult airway: a comparison with the Macintosh blade. Eur J Anaesthesiol. 2009;26: Sun DA, Warriner CB, Parsons DG, Klein R, Umedaly HS, Moult M. The GlideScope Video Laryngoscope: randomized clinical trial in 200 patients. Br J Anaesth. 2005; 94: Griesdale DE, Liu D, McKinney J, Choi PT. Glidescope video-laryngoscoppy versus direct laryngoscopy for endotracheal intubation: a systematic review and meta-analysis. Can J Anesth 2012; 59: Cavus E, Thee C, Moeller T, Kieckhaefer J, Doerges V, Wagner K. A randomised, controlled crossover comparison of the C-MAC videolaryngoscope with direct laryngoscopy in 150 patients during routine induction of anaesthesia. BMC anesthesiol 2011;11: Cavus E, Neumann T, Doerges V, Moeller T, Scharf E, Wagner K et al. First clinical evaluation of the C-MAC D-Blade videolaryngoscope during routine and difficult intubation. Anesth Analg 2011;12: Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J. 1985;32: Bellhouse CP, Dore C. Criteria for estimating likelihood of difficulty of endotracheal intubation with the Macintosh laryngoscope. Anaesth Intensive Care. 1988;16:

14 14. el-ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich AD. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg. 1996;82: Patil V, Stehling, LC, Zaunder, HL. Predicting the difficulty of intubation utilizing an intubation guide. Anesthesiology. 1983;10: Yentis S, Lee D. Evaluation of an improved scoring system for the grading of direct laryngoscopy. Anaesthesia. 1998;53: Henthorn R, Red J, Szafranski J. Combining the fibreoptic bronchoscope with a laryngoscope blade aids teaching direct laryngoscopy. Anesth Analg. 1995;80: Cooper RM, Pacey JA, Bishop MJ, McCluskey SA. Early clinical experience with a new videolaryngoscope (GlideScope) in 728 patients. Can J Anaesth. 2005;52: Shippey B, Ray D, McKeown D. Use of the McGrath videolaryngoscope in the management of difficult and failed tracheal intubation. Br J Anaesth. 2008;100: Benjamin FJ, Boon D, French RA. An evaluation of the GlideScope, a new video laryngoscope for difficult airways: a manikin study. Eur J Anaesthesiol. 2006;23: Lim Y, Yeo SW. A comparison of the GlideScope with the Macintosh laryngoscope for tracheal intubation in patients with simulated difficult airway. Anaesth Intensive Care. 2005;33: Kaplan MB, Hagberg CA, Ward DS, Brambrink A, Chhibber AK, Heidegger T et al. Comparison of direct and video-assisted views of the larynx during routine intubation. J Clin Anesth. 2006;18: Cooper RM. Complications associated with the use of the GlideScope videolaryngo-scope. Can J Anaesth. 2007;54: Benumof JL. Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology. 1991;75: Samsoon G, Young J. Difficult tracheal intubation: a retrospective study. Anaesthesia. 1987;42: Arne J, Descoins P, Fusciardi J, Ingrand P, Ferrier B, Boudigues D, et al. Preoperative assessment for difficult intubation in general ENT surgery: predictive value of a clinical multivariate risk index. Br J Anaesth. 1998; 80:140-6.

15 LEGENDS OF FIGURES Figure 1: Laryngoscopes From left to right: a) Conventional laryngoscope with Macintosh blade size 4 b) GlideScope videolaryngoscope Large c) D-Blade for C-MAC videolaryngoscopic system Figure 2: Laryngoscopic views Table 1: Demographic data Table 2: Predictors for a potentially difficult airway Table 3: Times for laryngoscopy and intubation, numbers of intubation attempts and intubation success rates.

16 Figure 1 From left to right: a) Conventional laryngoscope with Macintosh blade size 4 b) GlideScope videolaryngoscope Large c) D-Blade for C-MAC videolaryngoscopic system

17 Figure 2: Laryngoscopic views C/L 1 C/L 2a C/L 2b C/L 3 C/L 4 DL DB GS Data are given in percentage, n = 95 C/L indicates Cormack and Lehane view, modified by Yentis and Lee p < 0.05 DB vs. DL; p < 0.05 GS vs. DL

18 Table 1: Demographic data Demographic data Direct Laryngoscope (n = 32) C-MAC D-Blade (n = 32) GlideScope (n = 32)* Entire collective (n =96) Height (cm) 171 ± ± ± ± 10 Weight (kg) 76 ± ± ± ± 16 Age (yr) 59 ± ± ± ± 16 Sex (f:m) 16:16 7:25 8:24 31:65 ASA-class I/II/III 2/19/11 3/21/8 0/21/11 5/61/30 Data are given as mean ± SD, or absolute numbers. * One patient had to be excluded from further investigation due to problems with face mask ventilation,

19 Table 2: Predictors for a potentially difficult airway Predictors Direct Laryngoscope (n = 32) C-MAC D-Blade (n = 32) GlideScope (n = 32)* Entire collective (n =96) Mallampati class (I / II / III / IV) 0/20/9/3 1/16/11/4 1/16/13/2 2/52/33/9 Mouth opening [cm]: 4,1 ± 0,8 4,0 ± 0,9 4,0 ± 0,7 4,0 ± 0,8 <4cm / 4cm 10/22 10/22 9/23 29/67 Thyromental distance [cm]: 8,0 ± 2,2 7,6 ± 1,4 7,4 ± 2,1 7,7 ± 1,9 <6cm / 6cm 1/31 2/30 4/28 7/89 Mobility of atlanto-occipital junction: < 15 / > 15 4/28 1/31 4/28 9/87 Number of patients with 2 predictors Data are given as mean ± SD, or absolute numbers. * One patient had to be excluded from further investigation due to problems with face mask ventilation,

20 Table 3: Times for laryngoscopy and intubation, numbers of intubation attempts and intubation success rates. Group Direct D-Blade-CMAC GlideScope Laryngoscopy Laryngoscopy (n =95) (n=95) (n =95) time (sec) 13,2 ± 6,3 [ ] 10,8 ± 4,3 [ ] 12,0 ± 5,8 [ ] Intubation (n =32) (n =32) (n =31) first attempt 27 (84) 27 (84) 29 (94) second attempt 1 (3) 4 (13) 1 (3) third attempt 0 1 (3) 1 (3) failed 4 (13) 0 0 time* (sec) 11.2 ± 5.6 [ ] 17.7 ± ± 14.0 [8.0 33] + [9,0 34,0] ++ # Data are given as mean ± SD [range] or in absolute number (percentage) * Intubation time measurements did not include cases of failed intubation + p < 0.05 vs. DL, ++ p < 0.05 vs DL, # n.s. vs. DB