Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake ((V) over dot O-2max): two with 20.95+/- 0.28% O-2 and the third (GXT(40)) while breathing hyperoxia (40.64 +/- 1.29% O-2). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (POmax) in the second trial (GXT(21)). Compared to GXT(21), hyperoxia significantly increased (V) over dot O-2max and POmax by 10.0 +/- 3.8% and 10.2 +/- 7.1%, respectively. This was likely due to an increase in O-2 delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in (V) over dot O-2max with hyperoxia was similar to the increase in carbon dioxide production ( 9.3 +/- 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited (V) over dot O-2max in GXT21, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT40, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.