374 Short report

In a difficult access scenario, supraglottic airway devices improve success and time to ventilation Wolfgang A. Wetscha, Andreas Schneidera, Robert Schiera, Oliver Speltena, Martin Hellmichb and Jochen Hinkelbeina The success of tracheal intubation (TI) is unacceptably low in unconventional positions. Supraglottic airway devices (SAD) have become an important alternative. An airway manikin was placed in a car, simulating an entrapped motor vehicle accident victim. The rescuer only had access through the driver’s door. Participants were (n = 25) anaesthesiologists with experience in prehospital emergency medicine. They attempted to secure the airway by TI or an SAD (Ambu AuraOnce, iGel, laryngeal tube) in a random sequence. Performance was compared using the Wilcoxon signed-rank test. P values less than 0.05 were considered statistically significant. Fastest effective ventilation was achieved with iGel (11.5 ± 6.9 s, P < 0.001), followed by a laryngeal mask (15.1 ± 5.6 s, P < 0.001) and a laryngeal tube (17.6 ± 5.3 s, P < 0.001); TI was the slowest (42.8 ± 23.9 s, comparator). iGel (P < 0.001) and laryngeal mask (P = 0.01) also significantly outperformed the

laryngeal tube. First ventilation was achieved significantly faster with SADs compared with TI. Success rates were also higher when using SADs. European Journal of Emergency Medicine 22:374–376 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

Introduction

The aim of this study was to test whether the use of SAD facilitates ventilation faster than emergency TI in entrapped patients when performed by experienced anaesthesiologists.

Airway management is crucial in many emergency situations. Patients with insufficient breathing efforts, inadequate or insufficient ventilation or reduced level of consciousness, for example, after a severe trauma or traumatic brain injury, require initiation of mechanical ventilation on site. Tracheal intubation (TI) is considered the gold standard for securing the airway. However, several trials have shown that intubation success is unacceptably low when performed by inexperienced personnel [1]. Therefore, supraglottic airway devices (SAD) are often recommended as alternatives for airway management [2]. In the out-of-hospital setting, environmental or situational conditions may complicate airway management. One particular difficulty is gaining access to entrapped patients after car accidents. If this patient requires emergency intubation, the situation is vastly different from TI in a controlled setting. Different approaches to TI have been described such as ‘ice-pick’ position, during which intubation is attempted face-to-face [3]. However, as most physicians are not used to and trained on such an approach, intubation success will be lower and attempts will require more time than in standard positions [4]. In a similar setting, it could be shown that the use of video laryngoscopes had no advantage over direct laryngoscopy in entrapped patients [4]. We hypothesized that both issues might be overcome by the use of SAD. 0969-9546 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

European Journal of Emergency Medicine 2015, 22:374–376 Keywords: emergency medicine, intubation, laryngeal mask, laryngeal tube, supraglottic airway a Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Cologne and bInstitute of Medical Statistics, Informatics and Epidemiology, University of Cologne, Cologne, Germany

Correspondence to Wolfgang A. Wetsch, MD, Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Cologne, Kerpener Str. 62, 50937 Cologne, Germany Tel: + 49 221 478 6283; fax: + 49 221 478 1488233; e-mail: [email protected] Received 5 July 2014 Accepted 4 November 2014

Methods Participants

Following ethical approval (Ethics Committee, University of Cologne; Prof. Lehmacher, Approval 10-182) and written informed consent, 25 anaesthesiologists (mean age, 35.2 ± 7.3 years; anaesthesia experience 9.1 ± 7.3 years) volunteered to participate. All were staff from our department, and were certified and active as EMS physicians, with a varying number of EMS shifts. Setting

A traffic accident with confinement of the driver was simulated with a manikin with advanced airway management possibilities (Ambu Airway Man; Ambu, Bad Nauheim, Germany) on the driver’s seat of a sports car (Mini Cooper S; BMW, Munich, Germany). Confinement was simulated by moving the driver’s seat all the way forward and in an upright position. Modifications to this scenario by moving the manikin and/or the seat were not allowed. Access to the manikin was only permitted through the opened driver’s door. All participants were instructed in the proper use of the devices: DOI: 10.1097/MEJ.0000000000000230

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Supraglottic airway devices Wetsch et al. 375

Participants were prompted to secure the airway of the manikin as quickly as possible; the four devices were used subsequently. To guard against bias because of training, each participant applied the devices in an individual random sequence generated by shuffling opaque envelopes. Data collection and statistical analysis

As the primary endpoint of this study, we measured the time needed from first handling of the airway device until successful ventilation; the latter was detected by a mechanical monitoring instrument, which is an integral part of the manikin. Secondary endpoints were the time until complete insertion of the airway device and the time until inflation of the cuff (if present). Furthermore, participants were asked to report the grade of the best glottic view that they were able to achieve during direct laryngoscopy using the Cormack/ Lehane classification. The reported value was recorded. Time was measured with a stopwatch. SPSS (IBM Corp., Armonk, New York, USA) and Stata (StataCorp, College Station, Texas, USA; user-written program Effcon) software was used for statistical analysis of the data. A sample size of 25 participants is sufficient to detect a medium (0.6) to large (0.8) effect size (standardized difference) in the primary endpoint ‘time to first ventilation’ (α = 0.05, β = 0.80, paired t-test). The Wilcoxon signedrank test for paired observations was used to compare the performance of the different devices. P values less than 0.05 were considered statistically significant. Moreover, the Bonferroni–Holm procedure was applied to guard against type I error inflation.

Fig. 1

150 Time to effective ventilation (s)

(1) Macintosh laryngoscope (Heine, Herrsching, Germany) and ID 7.5 mm tracheal tube with a malleable stylet; (2) Ambu AuraOnce laryngeal mask (Ambu, Bad Nauheim, Germany); (3) Laryngeal tube (VBM, Sulz, Germany); and (4) iGel laryngeal mask (Intersurgical, St Augustin, Germany).

Reference

∗∗∗

∗∗∗

∗∗∗

100

50

0 Macintosh

Laryngeal Laryngeal mask tube Device

iGel

Time (s) until first effective ventilation could be achieved. Results are expressed as median, first/third quartile (boxes), minimum/maximum except outliers (whiskers). White dots show the performance of participants. Differences between groups were analysed using the Wilcoxon signed-rank test (***P < 0.001).

In terms of the secondary endpoints, insertion of the airway device also took the shortest time with the iGel laryngeal mask, followed by the Ambu laryngeal mask, laryngeal tube and tracheal tube. The block of the devices’ cuff was successfully achieved fastest with the Ambu laryngeal mask, followed by laryngeal tube and tracheal tube (the iGel does not need to be blocked and hence has no inflatable cuff). During TI, the best possible glottic view, expressed as the Cormack/Lehane score, was distributed as 1 (n = 5), 2 (n = 19) and 3 (n = 1).

Discussion Results Effective ventilation was achieved fastest with the use of the iGel, followed by a laryngeal mask and a laryngeal tube (Fig. 1). iGel (mean ± SD 11.5 ± 6.9 s; P < 0.001), laryngeal mask (15.1 ± 5.6 s; P < 0.001) and laryngeal tube (17.6 ± 5.3 s; P < 0.001) facilitated the first effective ventilation significantly faster than TI (42.8 ± 23.9 s), resulting in an effect size of 1.4 (95% confidence interval 0.9–2.0) between iGel and TI. iGel (P < 0.001) and laryngeal mask (P = 0.01) also significantly outperformed the laryngeal tube, with iGel facilitating ventilation faster (P = 0.004) than the laryngeal mask. All these comparisons remained significant when corrected for multiple testing (Bonferroni–Holm procedure). TI required more than twice the time of the insertion of a SAD. All times are presented in Table 1.

All participants could successfully ventilate the manikin with each of the different devices. However, ventilation was achieved significantly faster with the use of SAD. Time is a crucial factor in emergency airway management. Administration of 100% oxygen may lead to an increase in the arterial oxygen partial pressure (PaO2) from 80 to 400 mmHg in patients undergoing elective procedures in anaesthesia – however, the same preoxygenation procedure may only lead to an increase in the PaO2 from 67 to 104 mmHg in critically ill emergency patients [5]. This may lead to a critical decrease in oxygen saturation during TI. The use of SAD might help to minimize this risk. The risk of aspiration must be outweighed with the duration until oxygenation of the patient is possible.

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European Journal of Emergency Medicine 2015, Vol 22 No 5

Table 1 Time needed until complete insertion of the device, until inflation of the cuff (if applicable) and until the first effective ventilation with the corresponding devices Time until complete insertion (s) Macintosh Laryngeal mask Laryngeal tube iGel

26.0 5.8 6.0 5.4

Time until inflation of the cuff (s)

(16.7–30.8) (4.5–7.5) (4.3–8.5) (3.8–6.5)

31.3 (19.9–44.0) 9.8 (7.1–11.3) 10.8 (8.7–13.4) NA

Time until first ventilation (s) 37.9 13.6 17.3 9.7

(27.2–48.7) (10.3–17.6) (13.6–20.0) (8.0–11.6)

Results are expressed as median (25th–75th percentile).

Conclusion

Success rate

It has been shown that the rate of failed TI may be as high as 31% when performed by nonanaesthesiologists in the out-of-hospital setting [6]. Even when performed by experienced physicians, it could be shown that the rate of unrecognized tracheal tube misplacement was as high as 17.4%, with the rate of oesophageal intubations at 6.7% [7]. In particular, unrecognized oesophageal intubation of the paralysed patient is life-threatening. However, the use of SAD has been shown to have high success rates, even when used by less experienced or less trained personnel [8]. Several studies have shown that SAD can be handled easily by most caregivers even without previous experience in airway management in different emergency situations [9]. SADs provide reliable and effective ventilation and they protect against aspiration to a certain degree [10]. However, it has to be considered that ventilation might not always be achieved with SAD. Risk factors for ventilation failure include obesity, male sex or positioning other than a supine one. Earlier studies from our group showed that the use of video laryngoscopes did not help to facilitate TI faster, nor did it help to improve the success rate of TI in the same setting [4].

Limitations

This study was carried out with a standardized airway manikin. Insertion of SAD may be more difficult in patients. Blood, saliva, vomitus, etc. may complicate the use of the devices. However, the same is true for TI. Furthermore, the collective of our participants was quite experienced in airway management. Results might vary when devices are used by less experienced personnel.

We conclude that TI of entrapped car accident victims is feasible for experienced anaesthesiologists using a standard Macintosh laryngoscope, but leads to a remarkable delay until first ventilation. Therefore, SAD should be considered as a first-line alternative or they must at least be stockpiled as a second-line airway in cases of failed intubation.

Acknowledgements Conflicts of interest

J.H. has received travel expenses from Ambu GmbH, Germany, during the last 5 years. For the remaining authors there are no conflicts of interest.

References 1

Katz SH, Falk JL. Misplaced endotracheal tubes by paramedics in an urban emergency medical services system. Ann Emerg Med 2001; 37:32–37. 2 Truhlar A, Ferson DZ. Use of the laryngeal mask airway supreme in prehospital difficult airway management. Resuscitation 2008; 78:107–108. 3 Hilker T, Genzwuerker HV. Inverse intubation: an important alternative for intubation in the streets. Prehosp Emerg Care 1999; 3:74–76. 4 Wetsch WA, Carlitscheck M, Spelten O, Teschendorf P, Hellmich M, Genzwürker HV, Hinkelbein J. Success rates and endotracheal tube insertion times of experienced emergency physicians using five video laryngoscopes: a randomised trial in a simulated trapped car accident victim. Eur J Anaesthesiol 2011; 28:849–858. 5 Mort TC. Preoxygenation in critically ill patients requiring emergency tracheal intubation. Crit Care Med 2005; 33:2672–2675. 6 Cobas MA, De la Peña MA, Manning R, Candiotti K, Varon AJ. Prehospital intubations and mortality: a level 1 trauma center perspective. Anesth Analg 2009; 109:489–493. 7 Timmermann A, Russo SG, Eich C, Roessler M, Braun U, Rosenblatt WH, Quintel M. The out-of-hospital esophageal and endobronchial intubations performed by emergency physicians. Anesth Analg 2007; 104:619–623. 8 Bosch J, de Nooij J, de Visser M, Cannegieter SC, Terpstra NJ, Heringhaus C, Burggraaf J. Prehospital use in emergency patients of a laryngeal mask airway by ambulance paramedics is a safe and effective alternative for endotracheal intubation. Emerg Med J 2014; 31:750–753. 9 Grier G, Bredmose P, Davies G, Lockey D. Introduction and use of the ProSeal laryngeal mask airway as a rescue device in a pre-hospital trauma anaesthesia algorithm. Resuscitation 2009; 80:138–141. 10 Bercker S, Schmidbauer W, Volk T, Bogusch G, Bubser HP, Hensel M, Kerner T. A comparison of seal in seven supraglottic airway devices using a cadaver model of elevated esophageal pressure. Anesth Analg 2008; 106:445–448, table of contents.

Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.

In a difficult access scenario, supraglottic airway devices improve success and time to ventilation.

The success of tracheal intubation (TI) is unacceptably low in unconventional positions. Supraglottic airway devices (SAD) have become an important al...
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