Minimal increases in pulmonary wedge pressure associated with improved PaO2s in dogs

To determine the relationship between minimal increases in pulmonary wedge pressure (PWP), arterial PO2s, single breath diffusing capacity (DLCO), and lung perfusion pattern (as determined by semiupright lung scans), we elevated PWP by 61.8+/-4.1% from baseline values of 5.5+/-0.4 mm Hg. At the end of 30 min PaO2 increased by 13.2+/-1.4% (p less than 0.001) from baseline values of 81.7+/-3.1 mm Hg; DLCO decreased by 15.5+/-1.2% (p less than 0.01) to 0.98+/-0.10 ml/min/mm Hg/kg. Lung perfusion changes in the right lung apical zone increased by 28.0+/-4.2% (p less than 0.001) and decreased in the basal zone by 6.2+/-0.8% (NS). In the left lung the apical perfusion increased by 14.9+/-1.1% (p less than 0.01) and basal perfusion decreased by 8.6/+-1.4% (NS). We conclude that minimal elevation of PWP in dogs leads to improvement in PaO2s through alterations in the lungs perfusion pattern.