Effect of the curvature of the O2 equilibrium curve on alveolar O2 uptake: theory.
The effect of the curvature of the O2 equilibrium curve (OEC), in the range between mixed venous and alveolar PO2, on alveolar O2 uptake was quantitatively investigated in a simple homogeneous lung model. The O2 uptake achieved with a linear OEC (Mlin) was subtracted from the O2 uptake (M) attained with the physiologically curved, sigmoid OEC, and the relative difference was considered as the 'curvature effect', CE [= (M - Mlin)/M], indicating, if positive, the enhancement of O2 uptake by the non-linearity of the OEC. Calculations show CE to be close to nil (less than 1%) in normal lungs during rest both in normoxia and in hypoxia. CE is more important in heavy exercise both in normoxia (CE less than 19%) or slight hypoxia (CE less than 15%). In deep hypoxia, CE is negligible again even during exercise. Thus, the simplified approach to the analysis of alveolar O2 uptake using a linear OEC, in the mixed venous-to-alveolar PO2 range, constitutes in most cases a valid approximation.
Kobayashi
H
H
Institut für Physiologie, Ruhr-Universität Bochum, F.R.G.
Piiper
J
J
Scheid
P
P
D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000378:metabolism*
D010100:Oxygen