Effects of Elevated Core Temperature and Normoxic 30% Nitrous Oxide on Control of Human Breathing during Short Duration, High Intensity Exercise

It is unresolved how pulmonary ventilation (VE) is influenced by normoxic 30% nitrous oxide (N2O) breathing and hyperthermia during supramaximal intensity exercise. It was hypothesized that normoxic N2O will suppress and hyperthermia will increase exercise ventilation, timing and ventilatory drive during supramaximal intensity exercise. Seven college-aged males volunteered for 4 separate 30 s Wingate cycle ergometer tests. The studies included a 2 x 2 design with factors of Thermal State (normothermia or hyperthermia) and Gas Type (Air or normoxic 30% N2O). A significant interaction (F=8.4, p=0.03) between these 2 factors for VE was explained by a VE from 85 ± 27 L/min (p=0.06) during normothermia with N2O to a VE of 104 ± 23 L/min in hyperthermia with N2O. There were no main effects or interactions for Thermal State and Gas Type for timing components and ventilatory drive. In conclusion, an interaction of Thermal State and Gas Type on VE was explained by its suppression during normothermia relative to its rate in hyperthermia, both during normoxic N2O breathing during supramaximal intensity exercise.