Effect of bronchial and arterial constriction on alveolar gas concentrations in a lobe of the dog's lung

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

Gas concentration tracings were obtained with a mass spectrometer by sampling in the left lower lobe bronchus of open-chested dogs ventilated by a plethysmograph. Partial bronchial obstruction and/or arterial obstruction could be produced by tightening clamps on the bronchus and the branch of the pulmonary artery supplying the lobe. Characteristic patterns of oxygen, carbon dioxide and argon concentration (following a single inspiration of an argon-air mixture) were found with partial bronchial obstruction, arterial obstruction and a combination of both. The patterns were explained by alterations in the ventilation-perfusion ratio and in the phase of ventilation of the obstructed lobe. By relating the tracing taken during mixed obstruction to the pressure cycle of the plethysmograph, some mechanical properties of the obstructed lobe were derived.