Assessment of Impaired Pulmonary Circulation : Effects of Gravity on Regional Pulmonary Arterial Blood Flow in Various Cardiac and Pulmonary Diseases Studied by External Radioisotope Scanning

Studies on influence of gravity between the supine and the upright distributions of regional pulmonary arterial flow indicated that cardiac and pulmonary diseases were divided into three groups according to impaired pulmonary circulation. In severe cases with pulmonary vascular d, isorders showing marked pulmonary hypertension and probably indicating the organic changes in pulmonary vessels, both gravitational change and change ratio were extremely decreased ; these cases were called "perfect form of impaired pulmonary circulation". There were the cases with decreased gravitational change but normal gravitational change ratio; these cases which may have elevated intravascular pressure but keep some distensibilities of vessels were called "imperfect form". There were of course the cases with the same gravitational change and change ratio as those of normal subjects ' these cases with normal hemodynamics were called "normal form". Further study on upper to lower ratio, correlating with pulmonary venous pressure, was able to divide perfect form into two groups. This suggested that postcapillary pulmonary hypertension might be differentiated from precapillary hypertension.