Effects of increased pulmonary vascular tone on gas exchange in canine oleic acid pulmonary edema

Abstract

Pulmonary gas exchange was investigated before and after an increase in pulmonary vascular tone induced by administration of acetylsalicylic acid (ASA), indomethacin, or almitrine in 32 pentobarbital-anesthetized and ventilated (fraction of inspired O2 0.4) dogs with oleic acid lung injury. Pulmonary vascular tone was evaluated by five-point pulmonary arterial pressure (PAP)/cardiac index (Q) plots and intrapulmonary shunt was measured using a SF6 infusion. PAP/Q plots were rectilinear in all experimental conditions. In control dogs (n = 8), oleic acid (0.09 ml/kg iv) increased PAP over the range of Q studied (1-5 l.min-1.m-2). At the same Q, arterial PO2 fell from 186 +/- 11 to 65 +/- 8 (SE) Torr and intrapulmonary shunt rose from 5 +/- 1 to 50 +/- 6% 90 min after oleic acid injection. These changes remained stable during the generation of two consecutive PAP/Q plots. ASA (1 g iv, n = 8), indomethacin (2 mg/kg iv, n = 8), and almitrine (8 micrograms.kg-1.min-1 iv, n = 8) produced a further increase in PAP at each level of Q. ASA and indomethacin, respectively, increased arterial PO2 from 61 +/- 4 to 70 +/- 3 Torr (P less than 0.05) and from 70 +/- 6 to 86 +/- 6 Torr (P less than 0.05) and decreased intrapulmonary shunt from 61 +/- 5 to 44 +/- 4% (P less than 0.05) and from 44 +/- 5 to 29 +/- 4% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)