Bronchospirometry. IV. Ambient-air and oxygen-recording bronchospirometry

Previous work on ambient air spirometry was reviewed, and its application to bronchospirometry was discussed. Three systems for ambient air breathing and continuous recording of respiratory excursions were described. The first permits constant room air breathing and recording of respiratory excursions, the second makes possible instantaneous switching to conventional oxygen rebreathing spirometry without interruption of recording, while the third allows for analysis of expired air after spirometry. A bronchospirometer was described which contains twin drum-balloon systems for room air and conventional oxygen recording spirometry, as well as visible, low-resistance, respiratory valves and ventilographs for integration of differential ventilation. Three normal volunteers were examined by ambient air bronchospirometry followed by conventional oxygen breathing. The relative oxygen uptake for the two lungs remained unchanged. Twelve patients with moderate unilateral pulmonary functional impairment due to bronchogenic carcinoma, hemothorax, tuberculosis, and surgical collapse or resection were studied. There was no difference of relative oxygen uptake of the involved lung on changing from room air to oxygen breathing. A third group of seven patients had severe unilateral pulmonary insufficiency due to far-advanced tuberculosis, hemofibrothorax, empyema, bronchogenic carcinoma with distal atelectasis, or congenital absence of one branch of the pulmonary artery. The mean oxygen uptake of the affected side was 3 per cent of the total on room air breathing and 12 per cent of the total on oxygen breathing. It was concluded that conventional oxygen bronchospirometry gives an incorrect impression of the functional participation of greatly damaged lungs but does not significantly alter results of bronchospirometry in normal volunteers and patients with but slight unilateral pulmonary involvement. The greater participation in oxygen uptake by the diseased lung on breathing an oxygen-enriched atmosphere was ascribed to an elevation of the oxygen tension in poorly ventilated alveoli sufficient to overcome the barrier of diseased alveolar membranes, and, in addition, pulmonary vasodilatation permitting a larger blood flow.