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 (Vdot;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 (PO max ) in the second trial (GXT 21 ). Compared to GXT 21 , hyperoxia significantly increased Vdot;O 2max and PO max 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 Vdot;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 Vdot;O 2max in GXT 21 , pulmonary ventilation and SCBA mask pressure were significantly lower during GXT 40 , suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.