Electrical activity of the human respiratory muscles during the action of various humoral influences on the respiratory center

The electrical activity of human inspiratory and expiratory muscles was studied in hypoxia, hyperoxia, and hypercapnia during added resistance to respiration. The results obtained confirmed that in man the inspiratory and expiratory zones are reciprocally related. This condition was distinctly demonstrated during changes of the arterial blood oxygen and carbon dioxide tensions. In hypoxic hypoxia and hypercapnia electrical activity of the inspiratory muscles was enhanced, and that of the expiratory muscles reduced. The reverse effect was obtained during the inhalation of pure oxygen.