Brief summary:
A clinical study of USASK AIRWAY - An Improved Oral Airway for Bag-mask Ventilation
A clinical study of MA AIRWAY - An Improved Oral Airway for Bag-mask Ventilation We report a study with University Research Ethics Board approval of a new oral airway device, the McKay Airway (MA), designed for easy maintenance of jaw-thrust (see illustration) for first responders who may perform bag-mask venti-lation (BMV) infrequently, and who often do not perform it well. Null hypothesis: naïve learners' time to achieve exhaled tidal volume (VE) >300ml will be no dif-ferent using MA than using a Guedel oropharyngeal airway (OPA) on anesthetized patients. Design was a repeated-measures unblinded controlled trial with blinded randomization of the order of airway use, comparing MA versus OPA conducted from July until December 2019. Anesthesiologists' decision to intervene and comments were recorded. Consenting learners included medical students, resi-dents from specialties other than anesthesiology, operating room staff, or naïve learners in technical courses scheduled in the operating rooms to be taught airway management. Patients were consenting adults booked for elective surgery under general anesthesia (GA). Excepted patients were those with loose incisors, tem-poromandibular joint disorders, reflux, those who did not wish to participate, and those whom the attending anesthesiologist felt put them at any added risk by par-ticipating. For patients with missing teeth, we padded the MA surface with 1cm thick stick-on sponge (Reston™ Self-Adhering Foam Pads; 3M, Maplewood MN USA). Patients were under the direct care of the consenting staff anesthesiologist for that OR. They were recruited in Pre-Admission Clinic, the hospital wards, Same-Day and Day-Surgery units, and in the OR holding area.
The experimental procedure included normal preoxygenation, induction of anesthesia, and BMV by the attending anesthesiologist as needed to assure high oxygen saturation prior to opening an opaque numbered envelope to randomly choose which airway to use first. We mimicked a self-inflating BMV device with the anesthetic machine by setting the Adjustable Pressure Limiting (APL) valve to >30cm water pressure and using the oxygen flush to ensure that the reservoir bag was filled between breath attempts. With the randomized airway in place, learners applied the mask with their left hand, squeezing the bag with their right approxi-mately every 3s. We timed from the first bag squeeze until VE exceeded 300ml, then repeated the experiment with the other airway. We approached 56 patients, recruited 34 female and 20 male, and obtained data for 51. One obese patient had severe succinylcholine fasciculations with rapid profound desaturation and the an-esthesiologist took over immediately, and for two the anesthesiologist misunder-stood the experiment. Time measurements were analysed with Wilcoxon's Signed Rank test, incidences with Fisher's Exact test or Chi Square. MA allowed faster adequate ventilation than OPA: Hodges-Lehmann median difference: 6s \[95% CI 5 to 6.3s\]; quartiles: OPA 9.5 to 37s; MA 7 to 16s range: OPA 5 to 78s; MA 2 to 49s; p = 0.02. When used first, the MA was faster than the OPA 30% of times compared to 11% when OPA was used first (p = 0.04), suggesting that MA may be easier to learn. Comments: 16 preferred the MA, 2 the OPA, and 15 had no preference (p = 0.02 compared to equal preferences). Further studies are warrant-ed.