Effect of oxygen inhalation on the respiration function during exercise under conditions of added resistance to respiration

Experiments were performed to investigate the effect of added resistance to inspiratory, expiratory and inspiratory-expiratory respiration on lung ventilation and pACO2 during exercise when breathing air or oxygen. Increase of resistance to respiration, particularly inspiratory-expiratory; reduced the work-induced growth of ventilation which caused pACO2 to increase. Oxygen inhalation aggravated those shifts significantly. The adverse effect of hyperoxia on the respiration function when exercise was combined with added resistance to respiration seems to be associated with inhibition of the respiration center produced by the lack of hyperoxid stimulation.