THE EFFECT OF UNILATERAL SPONTANEOUS PNEUMOTHORAX ON THE CIRCULATION IN MAN

Abstract

Studies of the circulation were made in 4 otherwise normal patients with spontaneous, unilateral pneumothorax. Studies were made at various stages of collapse and after complete expansion of the lung. Measurements of the body surface, O2 consumption, basal metabolic rate, arteriovenous O2 difference, cardiac output per min. and per beat, the heart rate, cardiac area, arterial blood pressure, cardiac work, circulation time, venous pressure, vital capacity, right and left lung area, and pneumothorax area were made. Cardiac output measurements were made by the acetylene method, 3 samples of gas being taken. Electrocardiograms were recorded and x-rays of the chest were taken at 2 m. All studies were carried out in the morning with the patient in a basal state. In 1 patient, estimations of the O2 content of the blood were made. The cardiac output was reduced in the presence of unilateral pneumothorax of small or moderate size, although it was sometimes unchanged or even increased. Patients exhibiting more extensive pneumothorax showed reduction in cardiac output which might be large or small. When the data for all cases were pooled, a rough linear correlation appeared between both cardiac output per min. and per beat, and % collapse of the lung, since the greatest collapse was associated with the greatest decrease in cardiac output. One patient was studied when there was only 14% collapse of one lung. The cardiac output was found to be increased in the presence of this small pneumothorax. The basal metabolic rate was on the low side of normal in all patients and 2 of them showed an appreciable lowering of the basal metabolic rate as the lung expanded. The arm to tongue circulation time and the venous pressure showed no consistent variation. The danger of inducing pneumothorax in subjects already suffering from lesions associated with a reduced cardiac output was pointed out.