The use of Bohr integral isopleths in the study of arterial oxygen saturation in chronic pulmonary tuberculosis.

Abstract

Data are presented from a group of 8 patients with respiratory insufficiency due to pulmonary tuberculosis. An improved method, using Bohr integral isopleths, was used for assessing the diffusing capacity of the differently ventilated and perfused lung spaces. Arterial oxygen unsaturation, when it occurred while the patient was breathing air, was due to inadequate oxygenation of blood in the slow space that washes out nitrogen slowly when oxygen is breathed. This in turn was due to either a low diffusing capacity, a low ventilation-perfusion ratio, or a combination of both in this space. The fast space of the lung did not contribute to arterial oxygen unsaturation in any of these patients. The alveolar-arterial oxygen tension gradients while the patient was breathing air were large, and were almost entirely due to disturbance of function in the slow space and not to shunting of blood.