GlideScope Macintosh

Transcription

1 Hong Kong Journal of Emergency Medicine Comparison of the GlideScope with the Macintosh laryngoscope in endotracheal intubation during uninterrupted mechanical chest compression: a randomised crossover manikin study GlideScope Macintosh FSH Yeung, RPK Lam, TW Wong, LW Chan Background: The GlideScope (GS) has been shown to improve the first-attempt success rate of endotracheal intubation during continuous mechanical chest compressions compared with the conventional Macintosh laryngoscope (ML) in inexperienced hands. Yet, its value for operators with experience of emergency airway management has remained uncertain. We set out to compare their performance in the hands of experienced operators in a manikin receiving continuous mechanical chest compressions delivered by LUCAS. Method: This was a randomised crossover study. Thirty-five emergency physicians and intensivists performed intubation using GS and ML in 3 different scenarios: (1) normal airway without chest compressions; (2) normal airway with uninterrupted mechanical chest compressions; and (3) normal airway with cervical spine (C-spine) immobilisation and uninterrupted mechanical chest compressions. The sequence of scenarios and devices used were randomised. The primary outcome was the first-attempt success rate of intubation. Other data including demographics, the time required for successful intubation, complications during intubation, the visual analog scale of perceived difficulty of intubation and the preference on devices in each scenario were also collected and analyzed. Results: In scenario 1, the first-attempt success rate with both laryngoscopes was 100%. In scenario 2, there was a higher first-attempt success rate with ML but it was not statistically significant (GS 97.14% vs ML 100%, p=1.00). In scenario 3, one participant failed to intubate in the first attempt with each of the laryngoscopes (GS 97.14% vs ML 97.14%, p=0.754). More dental compression was noted with GS but the difference was not statistically significant (GS 42.86% vs ML 22.86%, p=0.126). Overall, the median time for intubation with GS was significantly longer in all 3 scenarios (Scenario 1: GS 18.5s; interquartile range [IQR] s vs ML 11.2s, IQR s, p<0.001; Scenario 2: GS 18.7s, IQR s vs ML 13.4s, s, p<0.001; Scenario 3: GS 20.8s, IQR s vs ML 14.0s, IQR s, p<0.001). More participants preferred GS in scenario 3, while ML remained the device of choice in the other two scenarios. Conclusion: GS is not superior to ML in terms of the firstattempt success rate of intubation and it takes significantly longer to intubate for experienced operator. Yet more participants prefer its use when the C-spine motion is limited. Further studies are warranted to explore its role in trauma resuscitation. (Hong Kong j.emerg.med. 2016;23: ) Correspondence to: Yeung Sze Hoi, Frankie, MBBS, MRCS (A&E) Pamela Youde Nethersole Eastern Hospital, Department of Accident and Emergency, 3 Lok Man Road, Chai Wan, Hong Kong kieyeung@gmail.com Lam Pui Kin, Rex, FHKAM(Emergency Medicine), FHKCEM, Dip Clin Tox (HKCEM & HKPIC) Wong Tai Wai, MBBS, FRCSEd, FHKAM(Emergency Medicine) Chan Lap Wa, MRCP(UK), FHKCEM, FHKAM(Emergency Medicine)

2 160 Hong Kong j. emerg. med. Vol. 23(3) May 2016 GlideScope GS Macintosh ML LUCASR 3 GS ML ML GS97.14 ML 100 p= GS97.14 ML p=0.754 GS GS ML p= GS 1 GS 18.5s [IQR] s ML 11.2s IQR s p<0.001; 2 GS 18.7s IQR s vs ML 13.4s s p<0.001; 3 GS 20.8s IQR s vs ML 14.0s IQR s p< GS ML GS ML GS Keywords: Comparative study, equipment design, human, immobilization, time factor Introduction An effective and continuous chest compression is fundamental in cardiopulmonary resuscitation (CPR) of cardiac arrest patients. The 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care emphasized the importance of minimal interruption of chest compression during CPR until return of spontaneous circulation (ROSC) or termination of resuscitative efforts. 1 For endotracheal intubation, chest compressions should only be interrupted for the intubating provider to visualise the vocal cords and insert the tube, which should ideally take less than 10 seconds. 2 Theoretically, in experienced hands, it would be even better if the process of endotracheal intubation does not require any interruption of chest compressions at all. However, securing an advanced airway during uninterrupted chest compressions can be a challenge even to experienced emergency physicians and intensivists. Conventional direct laryngoscopic intubation using the Macintosh laryngoscope (ML) requires the alignment of the oral, pharyngeal and tracheal axes, which can be difficult to achieve during uninterrupted mechanical chest compressions because of the rapid relative movement of the glottis and the chest wall. In a manikin study by Gatward et al, it was found that chest compression delayed endotracheal tube placement using ML, and would require interruption of chest compressions for longer than 10 seconds. 3 On the other hand, the GlideScope (Saturn Biomedical System Inc, Burnaby, British Columbria, Canada) (GS) does not require the alignment of the oral-pharyngeal-tracheal axes. GS offers a better glottic view when compared with ML 4 and it has been proven to be useful in managing both simulated and real difficult airways, especially in the hands of inexperienced rescuers. 5,6 So far, studies on intubation during uninterrupted chest compressions have been rather limited, especially in the setting of mechanical chest compressions. Mechanical CPR using the Lund University Cardiopulmonary Assist System (LUCAS ) has become popular in local emergency departments and ICUs over the past few years. In view of that, we set out to conduct a randomised cross-over study to compare the performance of GS and ML in experienced hands in a manikin receiving continuous mechanical chest compressions delivered by LUCAS.

3 Yeung et al./intubation during uninterrupted CPR 161 Method This study was approved by the Hong Kong East Cluster Ethics Committee of the Hospital Authority. Medical officers from the Department of Accident and Emergency and the Department of Intensive Care of Pamela Youde Nethersole Eastern Hospital, who are regularly involved in CPR, were invited and recruited to our study. The subjects were informed of the details of the study and written consent for voluntary participation was obtained prior to recruitment. All participants were required to complete a questionnaire upon entry to the study, which collected demographic data, such as their specialties, posts, clinical experience, training status and the estimated number of emergency intubation per year. Participants could withdraw from the study at any time. Since GS remained relatively new to many emergency physicians and intensivists, a 30-minute one-to-one training session was provided to each participant. Each training session included a video demonstration of the proper use of the device (which spanned 3 minutes and 40 seconds in length), verbal instructions on the correct technique and hands-on practice. All participants were allowed to practise intubation with GS on the study manikin without limitation of the number of attempts. A participant was considered competent only if he or she could perform at least 5 successful endotracheal intubations with GS under the supervision of the investigators. Because of the steep learning curve of GS, 7,8 the authors believed such a training session was sufficient in familiarising the participants with its use. Each participant was then asked to perform endotracheal intubation on the study manikin with a normal airway (Laerdal Airway Management Trainer, Laerdal Medical AS, Stavanger, Norway) using ML and GS in 3 different scenarios: (1) normal airway without chest compressions; (2) normal airway with uninterrupted mechanical chest compressions; and (3) normal airway with cervical spine (C-spine) immobilisation and uninterrupted mechanical chest compressions. The order of the total 6 intubations performed by each participant was randomised in order to minimise the effect of learning. Each participant was asked to draw numbers from an opaque envelope to determine the sequence of intubations. Participants were not allowed to watch each other during the procedure to minimise the learning effect. The size 3 ML blade and the standard blade of GS were used in the scenarios. Cuffed endotracheal tubes with an internal diameter of 7.5 mm and malleable stylets were used for all intubations. For each intubation, all airway devices were lubricated in accordance with the manufacturers' instructions. All required equipment was placed next to the manikin's head. A nurse assistant was available in each scenario. The manikin was placed on a standard hospital stretcher with the head and neck in neutral position. Uninterrupted mechanical chest compressions were delivered using the gas-driven LUCAS with consistent frequency and depth of compressions. The setup of LUCAS was done by an emergency medicine specialist. C-spine immobilisation was performed by applying rigid neck collar, spinal board, sand bags and head straps to the manikin. Each participant was given a maximum of 60 seconds for each attempt. He or she was required to place the endotracheal tube and remove the stylet. Cuff Inflation, connection to a self-inflating bag and ventilation of the lungs of the manikin were done by the nurse assistant. There was no need to tie the tracheal tube in place. The use of external laryngeal manipulation to optimise the glottis view, such as cricoid pressure, was allowed as requested by the participant and was recorded. The time required to intubate was measured from the moment when the participant picked up the laryngoscopes to the moment when the stylet was completely removed from the endotracheal tube. The intubation attempt was considered successful if visible chest rise was seen on ventilation. Esophageal intubation or failed manual ventilation within 60 seconds was counted as a failed attempt. Each intubation attempt was timed by a third person consistently, who was not involved in data collection and analysis. The whole intubation process was videotaped and the time required for each intubation attempt was confirmed by reviewing the recorded video. For participants who required multiple attempts

4 162 Hong Kong j. emerg. med. Vol. 23(3) May 2016 in a given scenario, the total time needed to intubate was the sum of the time of each individual attempt. The primary outcome measure was the first-attempt success rate of intubation. Other outcome measures included the number of attempts required, the total time required for successful intubation in each scenario, and the occurrence of complications such as dental compression (signified by "clicking" sound produced by the manikin's teeth) and esophageal intubation. The perceived difficulty of intubation with each of the laryngoscopes was assessed by asking each participant to rate on a visual analog scale (VAS) from 0 mm (very easy) to 100 mm (very difficult) immediately after each scenario. Their preference of devices in each scenario was also assessed. All data were collected using a standardised data collection form. Since there was a lack of previous studies which could provide direct relevant figures for sample size calculation in the same experimental setting, we had difficulty in estimating the effect size. As a result, only a convenient sample of 35 doctors was recruited in our study. Categorical variables, such as the first-attempt success rate of intubation and the preference of devices were compared using the chi-square test or Fisher's Exact test, whenever appropriate. The Mann Whitney U test was used for continuous variables, such as the time required for successful intubation and the VAS of perceived difficulty, as both were not normally distributed. All statistical analysis was performed using the Statistical Package for Social Science (SPSS) version A p value less than 0.05 was considered as statistically significant. Results Thirty-five medical officers, including 27 (77.1%) emergency physicians and 8 (22.9%) intensivists, participated in the study. The mean age of the subjects was 34.9 years old (range 25 to 48 years old). The mean clinically experience was 10.3 years (range from 1 to 23 years) and more than half of them reported having performed more than 10 emergency intubations per year. The demographic characteristics of the subjects were summarised in Table 1. Scenario 1: Intubation without chest compressions All participants could intubate successfully without the need of external manipulation in the first attempt with either device (Table 2). The median time required for intubation was significantly longer with GS (GS 18.5s, IQR s vs ML 11.2s, IQR s, Figure 1) and more dental compression was noted though the difference was not significant statistically (Table 3). The median VAS of difficulty for both methods showed no significant difference, though there was a higher rating for GS (Table 4). Most participants preferred ML in this scenario (GS 2/35 vs ML 33/35). Table 1. Demographic characteristics of the study participants Gender Male 24 (69%) Female 11 (31%) Specialty AED 27 (77%) ICU 8 (23%) Qualification Trainee 15 (43%) Fellow 20 (57%) Intubation per year (17%) (20%) (26%) >20 13 (37%) Abbreviations: AED - Department of Accident and Emergency; ICU - Intensive Care Unit Table 2. Comparison of the first-attempt success rate of intubation in different scenarios Success rate of 1st Macintosh GlideScope P value attempt intubation Scenario 1 100% 100% N/A (35/35) (35/35) Scenario 2 100% 97.14% 1.00* (35/35) (34/35) Scenario % 97.14% 0.754* (34/35) (34/35) Footnotes: *Fisher's Exact test

5 Yeung et al./intubation during uninterrupted CPR 163 Scenario 2: Intubation with uninterrupted chest compressions One participant failed to intubate in the first attempt with GS while all succeeded with ML, but the difference in the first-attempt success rate was not statistically significant (Table 2). Two participants required external manipulation during intubation with ML while no manipulation was needed with GS. The median time required for intubation using either device was longer when compared with scenario 1 and it took significantly longer time to intubate with GS (GS 18.7s, IQR s, vs ML 13.4s, IQR s, Figure 1). Different from the first scenario, there were more dental compressions with ML but the difference was not statistically significant (Table 3). The median VAS of difficulty was again higher for GS, but the difference appeared to be smaller than in scenario 1 and was not statistically significant (Table 4). More participants still preferred ML but an increase in preference over GS was noted compared with scenario 1 (GS 11/35 vs ML 24/35). Scenario 3: Intubation with uninterrupted chest compression and C-spine immobilisation One participant failed to intubate in the first attempt with each device and the first attempt success rate was 97.14% for both laryngoscopes (Table 2). One participant required manipulation during intubation with ML while no manipulation was needed with GS, though the difference was not statistically significant. It took even longer to intubate with both devices in this scenario and the median time was significantly Footnotes: The data are given a median and interquantile range, with the bars representing the 10th and 90th centile. * indicates statistically significant difference. represents the outliers. MCL: Macintosch laryngoscope; GS: GlideScope. Figure 1. Box plot representing the time required for intubation with each device in each scenario.

6 164 Hong Kong j. emerg. med. Vol. 23(3) May 2016 longer with GS (GS 20.8s, IQR s, vs ML 14.0s, IQR s, Figure 1). More dental compression was also noted with the use of GS, though the difference was not statistically significant (Table 3). One esophageal intubation was noted with the use of ML. The VAS of difficulty was higher for ML but the difference was not statistically significant (Table 4). More participants preferred GS in this scenario (GS 22/35 vs ML 13/35). Discussion Designed to offer a better glottic view without the need to align the oral, pharyngeal and tracheal axes, GS has a theoretical advantage over the conventional ML in achieving a higher first-attempt success rate and a shorter time of intubation during uninterrupted chest compressions, especially in the difficult situation of C-spine immobilisation. Many manikin studies comparing GS with ML and various other videolaryngoscopes have demonstrated the advantage of GS in simulated difficult airway. 6,9-14 Yet contradictory findings are not uncommon in the Table 3. The rate of dental compression in different scenarios Complication rate Macintosh GlideScope P value Scenario % (4/35) 17.14% (6/35) 0.734* Scenario % (6/35) 11.43% (4/35) 0.734* Scenario % (8/35) 42.86%(15/35) 0.126** Footnotes: *Fisher's Exact test, **chi-square test Table 4. Comparison of the median visual analog scale (VAS) of perceived difficulty of intubation in different scenarios Mean difficulty Macintosh GlideScope P value by VAS Scenario 1 11 mm 18 mm 0.068* (1-22 mm) (7-28 mm) Scenario 2 25 mm 29 mm 0.365* (13-45 mm) (23-41 mm) Scenario 3 48 mm 42 mm 0.995* (21-69 mm) (24-64 mm) Footnotes: Values are presented in median (interquartile range). *Mann Whitney U test literature A detailed review of prior studies shows that GS appeared to perform better in operators with limited experience of intubation, such as medical students, inexperienced doctors and paramedics. 6,12-14 Such an advantage of GS was not consistently observed when experienced anesthetists or emergency physicians were recruited in the studies Furthermore, most studies did not involve chest compressions. The evidence in the setting of uninterrupted mechanical CPR has remained limited. Up till now, only a handful of published studies have been conducted in such a setting. The study by Shin et al showed that GS was more effective than ML in both normal and difficult airway, 20 but the study by Kim et al showed no difference. 21 The former study involved junior inexperienced interns while the latter recruited emergency doctors with experience of more than 50 intubations; both employed manual chest compressions delivered by a basic life support provider. In the setting of mechanical chest compressions delivered by LUCAS, Xanthos et al showed a significant higher cumulative success rate with GS but the study only involved inexperienced doctors. 22 It is not known whether these findings can be generalised to the emergency settings where doctors with experience in intubation are involved. In our study, no significant difference was found between GS and ML in terms of the first-attempt success rate of intubation in all three scenarios. These findings are contrary to those reported by Xanthos et al 22 but can be explained by the difference in the participants' experience in airway management. In their study, those with extensive experience in airway management were excluded and the recruited participants entered randomisation after performed only one successful intubation with each of the two laryngoscopes. The first attempt success rate with ML during continuous chest compressions was exceedingly low (44.4%), resulting in a noticeable difference in the cumulative success rate. Such a difference was not observed in our study when the intubations were performed by doctors with certain clinical experience in emergency airway management. In fact, our findings are more consistent with those reported in prior studies involving more experienced operators 21 and are

7 Yeung et al./intubation during uninterrupted CPR 165 supported by human studies, though the latter did not involve chest compressions. 5 Our study also showed that the use of GS resulted in a significantly longer median time of intubation in all three scenarios. It is obvious that more steps and physical motions are involved when GS is used. The operator needs to look into the mouth to insert the blade, then to the screen to advance the blade, and then into the mouth again to put in the endotracheal tube, then back to the screen to advance the tube past the vocal cords. The difficulty with tube manipulation under indirect vision probably accounts for the major proportion of the longer intubation time with GS. 23 The relative lack of experience in GS among the participants might also contribute to that. With more training and experience with GS, the time of intubation required may decrease. In scenario 3 where the C-spine was immobilised, GS is supposed to have the greatest advantage over ML because its design provides better a glottic view with less uplifting force and theoretically less neck movement. 24,25 This might explain the absence of esophageal intubation with GS while one esophageal intubation was noted with ML in this scenario. However, such merit was offset by the unacceptable high rate of dental compression (up to 42.86% of intubations) with GS, though the difference did not reach statistical significance. The more bulky design of the GS blade to accommodate the video camera and the optic fiber, together with the mouth opening further limited by the rigid neck collar, probably resulted in such a high dental compression rate. It is, however, interesting to note that there was a trend of preference shift from the ML to GS from scenario 1 to scenario 3. The more difficult the scenario was, the higher the preference over GS, even in a group of doctors whose prior experience in GS was rather limited. In scenario 3 where the intubation was the most difficult, the VAS on difficulty was higher for ML, though not statistically significant. Clearly more participants preferred GS despite the longer time required for intubation. The exact reason of these contradictory findings is not known. We believe that the perceived difficulty and the participants' preference on devices may not be solely dependent on the time required to intubate and the success rate, it may also depend on other factors such as the lifting force required and the operator posture during intubation. With GS, the operator can perform intubation in a standing position without the need of bending down and the lifting force is less when compared with ML. The participants might value these characteristics when they come to make their choice on the laryngoscopes. Some may argue that the Hawthorne effect might have caused bias in assessing the participants' preference as they might have modified their choice in favour of GS, having the knowledge that it was the key subject of our study. We tried to minimise that by allowing the participants to complete the questionnaire independently and the result was not known to the investigators until data entry and analysis. There was no "peer pressure" whatsoever and no secondary gain by stating preference on GS. Moreover, many participants came from another department (ICU) and there was simply no reason for them to please the investigators by altering their preference deliberately. We acknowledge that the Hawthorne effect could not be totally excluded in our study but its role in these contradictory findings has remained uncertain. The participants should also be asked about the reasons why they prefer one device over the other when assessing their preference in future studies. This study had several significant limitations. First, this was a manikin study. Although commonly used and accepted in previous studies to simulate effect on real patients, manikin itself cannot totally reproduce the laryngoscopic conditions, such as vocal cord movement, of the real patients under continuous chest compressions. It is well-recognised that the times to perform airway intervention are generally shorter in manikins than in real patients, especially in manikins with a normal airway. This may explain the high firstattempt success rate even during continuous mechanical CPR in our study. Yet the detrimental effect of CPR on intubation could still be reflected by a longer time required to intubate and a higher VAS of perceived difficulty across the scenarios. Given the practical and ethical hurdles of recruiting real patients in our locality, a manikin study was the only feasible design to allow comparison of the laryngoscopes in a

8 166 Hong Kong j. emerg. med. Vol. 23(3) May 2016 randomised protocol. Although we used the best available manikin model which has been validated and adopted in many studies in resuscitation, 26 it is not known whether the results could be extrapolated to real patients. Second, the condition simulated in scenario 3 represented a rare critical condition that not every emergency physician or intensivist would agree to intubate during continuous CPR or some may even argue on whether resuscitation should be carried out at all. While such decision remains a matter of individual judgement and is highly case-dependent, its rarity and high risk nature that had prompted us to identify effective means of intubation preemptively if one is to intubate the patient without interrupting CPR. Third, a rigid neck collar, instead of manual in-line immobilisation, was used for C-spine immobilisation during intubation. It was difficult to maintain C-spine immobilisation manually during continuous mechanical CPR using LUCAS. The use of rigid neck collar, together with the spinal board, sand bags and head straps, limited the neck movement better. Their use only increased the difficulty of intubation by limiting mouth opening as well, which might also explain the higher dental compression rate of GS in that scenario. Forth, the GlideScope-specific rigid stylet was not available in our department and the standard malleable stylet was used instead in the study. Previous studies have shown that both stylets are equally effective for GS use 27,28 and the results of our study should not be affected by the choice on the stylet. Fifth, GS had remained new to many participants. Despite its steep learning curve, it is not known with more experience, whether a higher success rate or a shorter time for intubation could be achieved. Finally, our study only focused on outcome measures such as the first-attempt success rate and the time required for intubation. Other theoretical advantages of GS, such as a potentially lower infective risk as there is no need for the operator to look directly into the patient's glottis during intubation, were not addressed. Further studies may be required to investigate the other theoretical advantages. Conclusion Based on the findings of our study, the previously demonstrated advantage of the GS over ML during uninterrupted mechanical CPR is not seen in experienced hands. It takes significantly longer to intubate in all three simulated scenarios. Yet more participants prefer its use when C-spine motion is limited. It may have a role in intubating patients with C-spine immobilisation undergoing mechanical CPR but further studies are warranted to explore its role in trauma resuscitation. Acknowledgements We sincerely thank Dr Yan, Wing Wa, the Chief-ofservice of the Department of Intensive Care, PYNEH, and our ICU colleagues for their support to the study. We also gratefully thank Ms Choi, Wing In and Mr Wong, Man Yin, the nursing staffs of the Department of Accident and Emergency, PYNEH, as our nursing assistants during the study. Competing interests All the equipment used was purchased by the Department of Accident and Emergency of Pamela Youde Nethersole Eastern Hospital long before the study. The investigators had received no sponsorship from the manufacturers in conducting the study. References 1. Field JM, Hazinski MF, Sayre MR, Chameides Leon, Schexnayder SM, Hemphill R, et al. Part 1: executive summary: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S Neumar RW, Otto CW, Link MS, Kronick SL, Shuster M, Callaway CW, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S Gatward JJ, Thomas MJ, Nolan JP, Cook TM. Effect of chest compressions on the time taken to insert airway devices in a manikin. Br J Anaesth 2008;100(3): Cooper RM, Pacey JA, Bishop MJ, McCluskey SA. Early clinical experience with a new videolaryngoscope (GlideScope) in 728 patients. Can J Anaesth 2005;52 (2):191-8.

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