The Nitrogen Clearance of the Lungs

Abstract

N elimination from the lungs during 02 breathing was followed in 5.0 normal subjects and in 150 patients with pulmonary disease. An alveolar N concentration of 2.5% was reached by the normal subjects in 5.5 minutes or less. The total ventilation used from the start of breathing 02 until this effect was obtained, the N washout volume, averaged 24 1, with 45 1 as the upper normal limit. The N washout volume increased with increasing age. In 50 emphysematous subjects the mean value for the N washout volume was 60 1; in 50 patients with chronic bronchitis without emphysema, 32.5 1; and in 50 silicotic subjects, 30.9 1. A rather crude correlation was found between N washout volume and functional residual capacity. The pulmonary emptying rate of Cournand et al may be more sensitive for discriminating normal from pathological air distribution if the alveolar N concentration is measured after a certain ventilation (e.g. 45 1) rather than after a certain time (e.g. 7 minutes) as originally proposed.