The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The effects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 +/- 0.22% O-2; SUB21) and hyperoxic (40.18 +/- 0.73% O-2; SUB40) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB21, hyperoxia significantly reduced minute ventilation ((V) over dot(E)), mask pressure (P-mask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB40. The reductions in both (V) over dot(E) and P-mask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 +/- 8.1% lower during SUB40 when compared to SUB21, another finding that has significant practical implications for occupational safety.