EFFECT OF OLEIC ACID-INDUCED PULMONARY-EDEMA ON PULMONARY AND CHEST WALL MECHANICS IN DOGS

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Abstract
Experimentally induced acute pulmonary edema causes changes in the pressure-(gas) volume characteristics of the lungs and the chest wall. These changes consist of a decreased functional residual capacity and an increased recoil pressure for lungs and chest wall at any given gas volume. With increased accumulation of liquid in the lungs, the gas becomes a relatively smaller component of intrathoracic lung volume. Rib cage magnetometer signals were used as an index of chest plus lung volume, compared to lung gas volume measured by He dilution, in relation to transpulmonary and transthoracic pressures before and after induction of acute pulmonary edema by infusion of oleic acid in 7 dogs. After infusion of oleic acid, functional residual capacity (normalized for body weight) decreased from a mean .+-. SD of 32.9 .+-. 5.5-16.8 .+-. 3.0 ml/kg (P < 0.001), and transpulmonary and transthoracic pressures were greater at any given volume above functional residual capacity, but rib cage magnetometer signals at functional residual capacity increased (P < 0.05), and rib cage magnetometer signals at any given transpulmonary and transthoracic pressures and of the descending limbs of the pressure-volume were unchanged. Although compliance of the lung measured between functional residual capacity and functional residual capacity + 600 ml decreased from a mean .+-. SD of 14.7 .+-. 2.5-9.4 + 2.2 ml/kg .cntdot. cm H2O (P < 0.0001) after infusion of oleic acid, compliance measured during deflation at higher lung volumes did not change, and chest wall characteristics did not change, as shown by unchanged transpulmonary pressure at any given rib cage magnetometer signal. Pressure-volume characteristics of the chest wall and the lungs are not altered, above the range of airway closure, with acute oleic acid-induced pulmonary edema.