Effect of oleic acid injury on lung-heart interaction during ventricular filling

Part of ventricular filling pressure is expended in deforming the lungs and oleic acid lung injury, which reduces lung compliance, might be expected to change the magnitude of this effect. Left ventricular pressure-volume curves from 13 treated and 13 uninjured dogs were compared. Curves were obtained by inflating a balloon in the flaccid left ventricle of the freshly dead dog. The extracardiac compliance component was determined by subtracting ventricular pressures observed when lungs were collapsed from those observed during inflation to levels duplicating both airway pressure and lung volume of uninjured dogs. We found that the respiratory system compliance opposing ventricular filling is much less than is predicted from the compliance opposing tidal ventilation. This suggests that cardiac filling imposes a local shape change rather than a general lung volume change. Injury only slightly decreased cardiac filling compliance although it markedly reduced lung inflating compliance. These results are consistent with citations showing that edema increases lung compliance by altering surface properties and airway closure with little change in tissue deformability. Thus, while edema may alter cardiac performance by changing pleural pressure, it has little influence on the pulmonary component of diastolic compliance.