Analysis of ventilatory response to CO2 during hypoxia in dogs.

Abstract

The response of the respiratory apparatus to CO2 during acute oxygen want was investigated in anesthetized dogs. The ratio of elevated ventilation to unit increase of PaCOCO2 in hypoxia to that in normoxia (SR) was taken as a measure of interaction between hypoxia and hypercapnia. Furthermore, the separate effect on ventilation by PaCOCO2 (DeltaAVR/DeltaPco2) and [H+] (DeltaAVR/DeltaH) during hypoxic hypercapnia was evaluated. a) SR increased in the presence of mild anoxia (80–50 mm Hg of PaOO2), then decreased in severe anoxia (less than 50 mm Hg of PaOO2). b) DeltaAVR/DeltaPco2 showed a higher value than the normoxia level in mild hypoxia (80–55 mm Hg of PaOO2), then progressively decreased with a further development of anoxia. c) DeltaAVR/DeltaH started increasing at about 70 mm Hg of PaOO2, then increased as the PaOO2 decreased, and reached about four times the normal at 30–40 mm Hg of PaOO2. The marked difference between isolated Pco2 and [H+] effect on ventilation in severe hypoxia suggested different areas and actions in the respiratory system of both chemical agents. separate effect of [H+] and Pco2 on ventilation Submitted on September 3, 1964