Lung volume and pleural pressure effects on ventricular function

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Abstract
To investigate the changes in ventricular function that occur during continuous positive-pressure ventilation, effects of separate increases in lung volume, pleural pressure and right ventricular afterload were studied in 15 dogs. Isovolume increases of pleural pressure caused changes in right and left ventricular hemodynamics indistinguishable from those induced by preload reduction. Lung distension with the chest open to atmosphere caused right and left atrial intracavitary pressures to rise as cardiac output fell, suggesting altered function of both ventricles. Raising right ventricular afterload by pulmonary artery constriction did not reprodu the hemodynamic changes observed during increases of lung volume. The apparent alteration of ventricular function that occurs during continuous positive-pressure ventilation may be produced by the associated increase in lung volume. Apparently, a right ventricular afterload-ventricular interdependence effect is not the responsible mechanism.