Observations on the haemodynamics of pulmonary and lobar atelectasis.

It is well recognized that air-absorption collapse of a iobe of a lung or a whole lung does not necessarily cause arterial anoxia. In the course of our investigation of the role of the anastomoses between the bronchial and pulmonary arteries described by Braus (1934), von Hayek (1940), Verloop (1948), Liebow, Hales, and Lindskog (1949), and Marchand, Gilroy, and Wilson (1950) in disease, we have confirmed this finding, and have made observations on the oxygen saturation of blood from the pulmonary arteries and veins during surgical resection of collapsed lobes. ARTERIAL OXYGEN SATURATION IN PULMONARY ATELECTASIS The eight patients investigated showed clinical and radiological evidence of complete absorption collapse of either a lung or a lobe of a lung. The duration of the history of respiratory disease varied from three weeks to five years. Samples of femoral arterial and venous blood were examined for oxygen unsaturation by the Haldane method as described by Douglas and Priestley (1937). The oxygen capacity of the blood was determined by haemoglobinometry. Stammers (1933) investigated the normal arterial oxygen saturation in Johannesburg (altitude 5,750 ft.) by the Van Slyke gas analysis method and found it to range from 92.6% to 97%. Sixteen clinically normal African negro subjects were used to test the accuracy of the Haldane method against Stammers's findings, and the arterial oxygen saturation in them was found to average 94.6%, ranging from 89% to 97%. Becklake (personal communication, 1950) investigated 10 normal negroes, using the Van Slyke gas analysis method and saturating the blood with oxygen to determine its oxygen capacity. She obtained values ranging from 91.0% to 93.5%, the average being 92.14%. In our eight patients, the arterial oxygen saturation ranged from 90% to 92%, and,can therefore be regarded as lying within the limits of normal. In none of our patients was there clinical evidence of cardiac involvement. In three, catheterization of the principal pulmonary arteries and the heart chambers showed pressures to be within normal limits.