EFFECT OF VARIATIONS IN BLOOD HYDROGEN-ION CONCENTRATION ON PULMONARY GAS-EXCHANGE OF ARTIFICIALLY VENTILATED DOGS

The effect of variation of blood hydrogen ion concentration on arterial and mixed venous PO2,ideal alveolar-arterial O2 pressure difference (PAiO2-PaO2),venous admixture (Qs/Qt), arterio-alveolar CO2 pressure difference (a-A)DCO2,physiological dead space to tidal volume ratio (VD/VT),cardiac output (Qt) and mean pulmonary arterial pressure ( {Mathematical expression}) has been studied. Arterial and mixed venous PO2increased and (PAiO2-PaO2)decreased with increasing blood hydrogen ion concentration. No change in (Qs/Qt), (a-A)-DCO2, VD/VT, Qt and {Mathematical expression} was observed. The effect of hydrogen ion concentration on arterial and mixed venous PO2and on (PAiO2-PaO2)is mainly due to a shift of the blood oxyhemoglobin dissociation curve (ODC), i.e. due to the Bohr effect. The upper part of the ODC is more flat in alkalosis (shift to the left) than in acidosis (shift to the right). Therefore the same end-capillary to arterial O2 content difference results in a greater (PAiO2-PaO2)in alkalosis than in acidosis. Any factor influencing the slope of the upper part of the ODC is expected to affect the arterial PO2and the (PAiO2-PaO2)by this mechanism. Similarly any factor shifting the steep part of the ODC is expected to affect the PO2of the mixed venous blood. © 1979 Springer-Verlag.