STUDIES ON INTRAPULMONARY MIXTURE OF GASES. IV. THE SIGNIFICANCE OF THE PULMONARY EMPTYING RATE AND A SIMPLIFIED OPEN CIRCUIT MEASUREMENT OF RESIDUAL AIR

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Abstract
The N conc. of a sample of alveolar air taken at the end of a period of pure O2 breathing provides an index of pulmonary emptying which is useful as a measure of effectiveness of ventilation. This procedure detects delayed pulmonary emptying, particularly in cases of pulmonary fibrosis and emphysema. Patients with such conditions have alveolar N concs., after 7 mins. of O2 breathing, above 2.5%; normal subjects and patients with chronic heart disease have values below 2.5%. A revised method for open circuit detn. of residual air, with simultaneous measurement of pulmonary emptying, is described; and 158 detns. by this method are presented and analyzed.