Safer oxygenation through flexible optical scopes during airway management: an in vitro study

PURPOSE: Oxygen insufflation through the working channel of flexible optical scopes improves oxygenation and visibility during tracheal intubation but potentially causes barotrauma when not pressure-restricted. Pressure limited to 30-40 cm H2O improves safety. We sought to conduct an in vitro study to develop a setup that delivers oxygen at desired pressures while maintaining sufficient flows to achieve the documented benefits.

METHODS: In the present in vitro study, we constructed a setup with equipment readily available in anesthesia locations, allowing regulation of the pressure at which oxygen is delivered at the distal end of the flexible optical scope. Pressure was regulated via the adjustable pressure-limiting valve and measured by immersion in water. We identified which combinations of set flow from the anesthesia machine and set pressure resulted in distal pressures of 10, 15, 30, and 40 cm H2O, respectively. We measured the resulting flows.

RESULTS: In flexible scopes with a channel diameter ≥ 2 mm, we obtained clinically relevant flows > 3 L·min-1 at pressure of 30-40 cm H2O.

CONCLUSIONS: Oxygen insufflation through a flexible optical scope at a targeted distal pressure is possible with ubiquitous anesthesia equipment. Scopes with a suction-/working-channel diameter ≥ 2 mm delivered clinically relevant flows > 3 L·min-1 at a pressure of 30-40 cm H2O. Thinner scopes delivered lower flows. These findings will guide future studies and the implementation of this setup in clinical practice.