Cardiac effects of increased lung volume and decreased pleural pressure in man.

The cardiac effects of increased lung volume and/or decreased intrathoracic pressure were assessed by radionuclide angiography in normal male subjects. Increased lung volume alone produced no change in left ventricular (LV) or right ventricular (RV) end-diastolic size. Decreasing intrathoracic pressure to -30 Torr with a Mueller maneuver led to increases in LV end-diastolic and end-systolic volumes, and to increases in RV diastolic area. LV ejection fraction did not change significantly but RV ejection fraction decreased with the Mueller maneuver. Increases in transmural central venous pressure were also noted with the Mueller maneuver. The effects of combining increased lung volume with the Mueller maneuver were similar to those with the Mueller maneuver alone. These effects are consistent with the hypothesis that producing large negative pleural pressures acts to impede left ventricular outflow (i.e., afterloading) and raises the possibility of similar changes during acute attacks of bronchospasm.