The effects of continuous positive airway pressure (CPAP) on the metabolic cost and work of breathing at rest, and during exercise, in healthy individuals wearing a gas mask

Ventilation may limit exercise. Wearing a gas mask may further compromise ventilation by increasing airway resistance. Continuous positive airway pressure (CPAP) improves ventilation by reducing airway resistance. The purpose of this study is to investigate the effects of a gas mask with and without CPAP on pattern, metabolic cost, and work of breathing (WOB) during resting and exercise conditions. We hypothesize that in healthy individuals, a gas mask will increase the metabolic cost of breathing and that the addition of CPAP to a gas mask will negate (reduce) said increases to the metabolic cost of breathing. Ten healthy males completed three testing regimes while wearing (i) a low resistance mask, or a NATO gas mask, (ii) without and (iii) with an attached portable CPAP device. Isocapnia was maintained in non‐exercise hyperventilation regimes. Respiratory, cardiovascular and metabolic parameters were measured. While wearing a gas mask during three levels of progressive aerobic exercise, the mean±SD VO2 was 0.93±0.13, 1.42±0.16 and 1.82±0.2 L/min. When the portable CPAP device was applied, the VO2 was reduced to 0.64±0.27, 1.11±0.27 and 1.46±0.42 L/min for the exercise condition (p<0.001 for all). The addition of CPAP to a gas mask reduces the metabolic cost of breathing during exercise conditions in healthy individuals. Funding provided by Thornhill Research Inc.