Rate of fall of O₂ tension in a lobe of dog lung after bronchial occlusion

¹ Department of Medicine, Postgraduate Medical School, Hammersmith Hospital, London, England

The oxygen tension in a lobe of the dog's lung following occlusion of the bronchus was measured with a mass spectrometer. The bronchus was rapidly blocked by inflating a small latex balloon just proximal to the tip of the mass spectrometer sampling tube sited in the bronchus. Cannulas in the branch of the pulmonary artery allowed the blood flow to the lobe to be continuously monitored on a rotameter, and direct measurements of flow were made by collection of timed samples. The rate of fall of O₂ tension following occlusion was approximately linear initially, and the rate correlated well with the direct measurement of perfusion when the animal was in a steady state. Preliminary trials suggest that the method can be used to compare lobar or segmental perfusion in different parts of the lung in man at bronchoscopy.