The Pentax Airway Scope (AWS; Hoya, Tokyo, Japan) is a videolaryngoscope reported to provide an indirect view of the airway. Studies indicate that the AWS is useful, not only for difficult airway management but also for emergent tracheal intubation with chest compressions in simulations.1 The McGrath MAC (McGrath; Aircraft Medical Ltd, Edinburgh, UK) is a device that has been developed with a high-resolution video camera, providing direct and indirect views of the glottis and reportedly useful in several difficult airways.2 Although the AWS and McGrath are both considered convenient tools for difficult or emergency airway management, no comparison of these two devices has been made during resuscitation.
The present study aimed to determine which of the two devices would improve intubation in simulations with chest compressions. We compared the performance of the AWS versus the McGrath with respect to tracheal intubation by anaesthesiologists during chest compressions in a manikin simulation.
This study was approved by the institutional review board of Osaka Medical College (No. 1321, approved on 6 January 2014; Chairperson: Ryuichi Saura), and written consent was obtained from each participant. Twenty-five anaesthesiologists with more than 2 years of clinical experience were recruited.
The SimMan3G (Laerdal, Sentrum, Stavenger, Norway) manikin was used to perform intubation and chest compressions. Either a size 4 blade of the McGrath or a standard Intlock blade of the AWS was used. Participants performed tracheal intubation using McGrath with both direct and indirect laryngoscopy. Tracheal tubes with an internal diameter of 7.5 mm were used. Chest compressions were demonstrated by the same Advanced Life Support instructor at a depth of about 5 cm and a rate of 100 compressions per minute in accordance with current guidelines.
Each participant was instructed to insert the tracheal tube, attach a bag valve mask and attempt to ventilate the lungs of the manikin. Intubation started when the participant picked up the AWS or McGrath and ended at the point of manual bag valve mask ventilation after tube insertion. Success or failure of tracheal intubation and intubation times were recorded for both tracheal and oesophageal intubations.
Results were compared using two-way repeated measures analysis of variance for intubation time, and Fisher's exact test for the success rate. Data are presented as mean ± standard deviations. A P value of less than 0.05 was considered statistically significant. The study was designed as a randomised cross-over trial to minimise the learning-curve effect resulting in a total of four interventions per participant (24 patterns) by a random number table. Results of a 10-doctor preliminary study showed that the time required to ventilate the lungs after successful insertion of the AWS was approximately 10 ± 3 s. To detect a 33% difference, we estimated that 18 participants would be adequate for two independent groups, whereby α = 0.05 and β = 0.2.
Selected participants had 4.9 ± 2.3 years of clinical experience in anaesthesia training. All participants had enough clinical experience using either the AWS or McGrath.
With the McGrath, no participant failed to achieve intubation without chest compressions, and one failed with compressions, which was not significantly different. With the AWS, all intubations were successful regardless of chest compressions. There were no significant differences in success rate between McGrath and AWS regardless of chest compression.
With the McGrath, tracheal intubation took significantly longer during chest compressions (13.1 ± 2.6 s) than without compressions (8.9 ± 1.4 s; P < 0.05). In contrast, chest compressions increased intubation time slightly, but not significantly, with the AWS (during compressions, 9.2 ± 1.1 s; without compressions, 8.7 ± 1.5 s). Intubation time without chest compressions did not significantly differ between the McGrath and AWS. The time required for intubation was significantly shorter during chest compressions with the AWS than with the McGrath (P < 0.05).
A previous study of anaesthesiologists unfamiliar with these laryngoscopes showed AWS superiority to McGrath for tracheal intubation.3 The present study in anaesthesiologists familiar with AWS and McGrath showed no significant difference for intubation performance without chest compression. Furthermore, a previous review about several viedolaryngoscope performances revealed that tracheal intubation time is generally shorter with AWS than with McGrath.4 In this study, the intubation time did not differ significantly between AWS and McGrath without chest compression. One probable reason is that the participants had enough clinical experience with these two devices.
During chest compression, the intubation time with the McGrath was significantly lengthened. In contrast, intubation time did not significantly increase with the AWS, and all anaesthesiologists were successful in intubating with this device during chest compressions. One probable reason for difficulties experienced with the McGrath is that the glottis, but not the tube, moved during chest compressions, and the relative positions of the glottis and tube were thus unstable. With the AWS, the tube and glottis move simultaneously and their relative positions remain the same, leading to easy and well tolerated tracheal intubation. Furthermore, a tracheal tube can be easily inserted through its built-in conduit.
This study has limitations worth noting. First, the simulations do not account for factors such as blood, vomit or sputum in the oropharynx. Second, use of these devices may be less than ideal in patients with severely restricted mouth opening.
We conclude that in adult simulations managed by anaesthesiologists, the AWS performed better than the McGrath for tracheal intubation with chest compressions.
Acknowledgements relating to this article
Assistance with the letter: none.
Financial support and sponsorship: financial support was provided by our institution.
Conflicts of interest: none.
1. Komasawa N, Ueki R, Itani M, et al. Validation of Pentax-AWS Airwayscope utility for intubation device during cardiopulmonary resuscitation on the ground. J Anesth
2. Taylor AM, Peck M, Launcelott S, et al. The McGrath( Series 5 videolaryngoscope vs the Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated difficult airway. Anaesthesia
3. Sharma DJ, Weightman WM, Travis A. Comparison of the Pentax Airway Scope and McGrath Videolaryngoscope with the Macintosh laryngoscope in tracheal intubation by anaesthetists unfamiliar with videolaryngoscopes: a manikin study. Anaesth Intensive Care
4. Niforopoulou P, Pantazopoulos I, Demestiha T, et al. Video laryngoscopes in the adult airway management: a topical review of the literature. Acta Anaesthesiol Scand