ACID-BASE STATUS AFFECTS GAS-EXCHANGE IN CANINE OLEIC-ACID PULMONARY-EDEMA

The effects of acidosis and alkalosis on pulmonary gas exchange were studied in 32 pentobarbital sodium-anesthetized intact dogs after induction of oleic acid (0.06 ml/kg) pulmonary edema. Gas exchange was assessed at constant ventilation and constant cardiac output, by venous admixture calculations and by intrapulmonary shunt measurements using the sulfur hexafluoride (SF6) method. Metabolic acidosis (pH 7.20) and alkalosis (pH 7.60) were induced with HCl and Carbicarb (isomolar Na2CO3 and NaHCO3), respectively. Hypercapnia was induced by adding inspiratory CO2, whereas pH was allowed to change (respiratory acidosis, pH 7.20) or maintained constant (isolated hypercapnia). Mean intrapulmonary shunt and pulmonary arterial minus wedge pressure difference, respectively, changed from 44 to 33% (P < 0.05) and from 9 to 10 mmHg (P > 0.05) in metabolic acidosis, from 44 to 62% (P < 0.001) and from 12 to 8 mmHg (P < 0.01) in metabolic alkalosis, from 40 to 42% (P > 0.05) and from 13 to 16 mmHg (P < 0.05) in respiratory acidosis, from 42 to 52% (P < 0.05) and from 8 to 12 mmHg (P < 0.01) in isolated hypercapnia. These results indicate that acidosis, alkalosis, and hypercapnia markedly influence pulmonary gas exchange and/or pulmonary hemodynamics in dogs with oleic acid pulmonary edema.