Comparison of ventilatory responses to sustained reduction in arterial oxygen tension vs. content in awake ponies

to sustained reduction in arterial oxygen tension vs content in awake ponies. J. Appl. Physiol. 76(5): 2147-2153, 1994.-To gain insight into central and peripheral contributions to changes in breathing during hypoxia, we compared effects on breathing of reducing inspired PO, (hypoxic hypoxia) with re-ducing arterial 0, content (Ca,J through elevation of carboxy-hemoglobin (COHb) (CO hypoxia). Twelve awake ponies were studied during 1 h of breathing room air followed by 6 h when COHb was increased to 25 % and CaoZ was decreased by 17%. When COHb was increased, arterial PCO, (Pa,oJ increased gradually to 1.3 Torr above (P < 0.05) control level between 30 and 45 min of CO exposure. Pulmonary ventilation (VE) de-creased (P = 0.09)-1 liter the first 30 min of CO exposure. After-45 min, Pa,, Torr below (P < 0.05