The pulmonary circulation in essential systemic hypertension.

Seventy-one men, ages 16 to 59 years, were referred for systemic hypertension, which was without detectable cause and with limited organ damage (World Health Organization stages I to II). They performed a graded exercise test on the bicycle ergometer in the sitting position. Mean brachial intraarterial pressure, mean pulmonary artery and wedge pressures and cardiac output (Fick method) were measured. At rest mean brachial artery pressure ranged from 72 to 168 mm Hg. Mean pulmonary wedge pressure was significantly (p less than 0.05) related to mean brachial artery pressure at rest, at submaximal work (50 watts) and at the end of exercise (161 +/- 42 [standard deviation] watts). In each subject pulmonary vascular resistance was calculated as the slope of the relation between the pressure gradient across the pulmonary circulation and cardiac output from data at rest, at 50 watts and at the end of exercise; mean critical closing pressure was calculated as the intercept of this relation. Pulmonary vascular resistance averaged 0.63 +/- 0.37 mm Hg/liter/min and was significantly related to age (r = 0.28, p less than 0.05) but not to rest brachial artery pressure (r = 0.14) or pulmonary wedge pressure (r = 0.09, difference not significant for both). The mean critical closing pressure averaged 6.1 +/- 4.0 mm Hg and was not related to brachial artery pressure (r = -0.08) or to age (r = -0.18, difference not significant for both). It is concluded that there is neither a primary nor a secondary effect of systemic hypertension on the pulmonary vasculature in patients with World Health Organization stages I to II essential hypertension.