Journal of Applied Physiology, Vol 65, Issue 2 788-796, Copyright © 1988 by American Physiological Society
Ventilatory response to CO2 and O2 near eupnea in awake dogs
W. W. Hwang, S. M. Yamashiro, D. Sedlock and F. S. Grodins
Department of Biomedical Engineering, University of Southern California, Los Angeles 90089-1451.
The problem faced in determining the ventilatory response to CO2 near
eupnea has been the difficulty of unloading metabolically produced CO2 from
the subject in the steady state. Previous methods using extracorporeal
circuits to unload CO2 are technically difficult and provide a limited
number of experimental states per experiment. Using the method of
high-frequency ventilation to unload CO2, we were able to obtain a large
number of determinations in the same subject under conditions of hypoxia,
normoxia, and hyperoxia. Data collected in five awake dogs show that the
ventilatory response to CO2 is linear down to apnea during normoxic
conditions but exhibits nonlinear behavior dependent on the level of
arterial O2 tension. During hyperoxic conditions, the response was concave
curvilinear, with a statistically significant decrease in slope near apnea.
In contrast, mild hypoxia led to a convex curvilinear response with an
increased slope near apnea.
