STUDIES OF PULMONARY HYPERTENSION I. PULMONARY CIRCULATORY DYNAMICS IN PATIENTS WITH PULMONARY EMPHYSEMA AT REST 1

Abstract

18 patients with pulmonary emphysema at rest were studied. The degree of pulmonary hypertension varied directly with the severity of emphysema, hypercapnia and anoxia. "Pulmonary capillary" pressure was normal in all cases. The pulmonary artery-"pulmonary capillary" pressure gradient exceeded normal in 11 patients and correlated significantly with pulmonary artery pressure and with the severity of hypercapnia. Total pulmonary resistance and pulmonary arteriolar resistance exceeded normal in all instances of pulmonary hypertension but correlated well only with the degree of CO2 retention. Cardiac output and index were variable. Cardiac index correlated negatively with the total pulmonary resistance. The O2 saturation of arterial blood varied inversely with mean pulmonary artery pressure but did not parallel the other determinants. The O2 tension of arterial blood did not vary predictably with any of the determinants. The CO2 tension of arterial blood correlated closely with mean pulmonary artery pressure, total pulmonary resistance and pulmonary arteriolar resistance, but not with the "pulmonary capillary" pressure. The ratio of residual volume to total capacity varied directly with mean pulmonary artery pressure and total pulmonary resistance. Certain mechanisms in the pathogenesis of pulmonary hypertension are discussed in detail. The role of anoxia is confirmed and attention is directed to the probable importance of CO2 retention in elevating pulmonary artery pressure and increasing pulmonary vascular resistance.