[Outdoor performance of different videolaryngoscopes on a glacier: a manikin study]

Little information about the performance of videolaryngoscopes outdoors is available. We aimed to test the hypothesis that a Macintosh direct laryngoscope would perform less well than videolaryngoscopes under difficult environmental conditions (high-altitude glacier, sun-reflecting snow).

After local research ethics committee approval, this randomized controlled trial enrolled 20 physicians who intubated manikins with limited cervical extension mouth opening under 5 conditions: 1) in hospitals (indoors), 2) indoors at a high altitude, 3) outdoors on a glacier in sunlight without sunglasses, 4) outdoors on a glacier with sunglasses, and 5) outdoors on a glacier with the physician and manikin covered with a blanket. The following devices were compared to the Macintosh laryngoscope, McGrath, Airtraq-SP, GlideScope, KingVision, C-MAC-D-Blade, AP Advance Difficult Airway Blade and Bonfils. The main outcome was first-attempt intubation success; secondary outcomes were intubation time, visibility on the screen, and view of the glottis.

The best intubation success rates were observed indoors asnd on the glacier under a blanket. The Macintosh performed better than the videolaryngoscopes under bright sunlight. We observed significant differences in the performance of devices with built-in screens under varying conditions. Wearing sunglasses improved performance with some but not all devices. Intubation times differed significantly between devices, regardless of the environmental condition (P<0.01). Screen visibility differed significantly between conditions and devices.

Successful intubation with videolaryngoscopes is less likely under bright sunlight conditions. The Macintosh laryngoscope performs better than videolaryngoscopes. Covering the heads of both the physician and the patient with a dark blanket sufficiently overcomes the detrimental effects of sunlight during intubation.