Effect of systemic venous hypertension on pulmonary function and lung water.

We studied the effects of systemic venous hypertension (SVH) of 25 cmH2O, with and without fluid overload (100 ml.kg-1.h-1 x 4 h), on the lung water content and pulmonary function of anesthetized dogs. SVH was produced by inflating a balloon in the right atrium. Pulmonary extravascular water (PEW) was measured by gravimetric techniques taking the water content of trapped blood into consideration. Subdivisions of lung volume, pulmonary resistance, dynamic compliance, and the single-breath nitrogen washout curve were performed in a body plethysmograph. Vascular pressures, serum oncotic pressure, and arterial blood gases were also measured. Systemic venous hypertension alone produced no change in lung water content (control PEW = 3.46 +/- 0.16; SVH PEW = 3.44 +/- 0.18 g H2O/g dry tissue, mean +/- SD) or alterations in pulmonary function. Fluid overload alone produced an insignificant increase in PEW (4.24 +/- 0.72 g H2O/g dry tissue) and decreases in vital capacity and functional residual capacity. SVH in combination with fluid overload resulted in a significant increase in lung water (4.78 +/- 1.03 g H2O/g dry tissue) and decreases in functional residual capacity, vital capacity, dynamic compliance, and arterial blood oxygen tension as well as increased pulmonary resistance. We conclude that SVH favors the formation of pulmonary edema under conditions of increased pulmonary transcapillary fluid exchange and may particularly augment airway edema.