Exploring the use of full-face masks for ventilation in dive rescue

Early oxygenation is essential in a non-breathing scuba accident victim, but the need to exclude water has thus far prevented underwater ventilation, causing significant delay. The full-face mask (FFM) is a potential solution, but its safety and feasibility in this context has not been established. This is a preliminary study into the utility of FFMs for underwater ventilation.

The tidal volume and peak inspiratory pressure delivered by the OTS Guardian and Neptune III FFMs were measured using a RespiTrainer Advance Airway Management Trainer and an open circuit scuba system. Ventilations were tested with varying lengths of purge valve depression and degrees of tightness of the FFM. A tidal volume of 350-560 mL was considered ideal. Thresholds considered to be high risk were 700 mL for volutrauma and peak inspiratory pressure > 3.4 kPa for barotrauma.

In all trials, the delivered pressure remained well below the 3.4 kPa threshold. The delivered volume was consistently less than 700 mL in at least one trial condition per FFM, although this required the fastest possible release of the Guardian purge valve without maximal mask tightening. The Neptune remained below 700 ml regardless of technique but required a one second purge valve depression to deliver sufficient volume (> 350 mL).

Recommendations need to be tailored to specific masks styles or brands. However, this form of ventilation could be feasible. Our findings are most directly applicable to ventilation at the surface. Further testing of these and other FFMs in simulation at depth will be necessary to evaluate the masks' use for ventilation. These results merit further investigation.