“Alveolar plateau” of the single breath nitrogen elimination curve in normal subjects

The single breath N 2 elimination test, as standardized by Comroe and Fowler, has been used in normal subjects. The N 2 difference, i.e. the difference in N 2 concentration between Ve = 1250 and Ve = 750 ml, showed a tendency to increase with increasing volumes of inspired O 2 and with increasing inspiratory flow rates. It decreased with increasing breath-holding time and was not consistently influenced by expiratory flow rate. The findings are compared with those of Fowler and of Shephard on normal subjects; different results were obtained, largely depending on different analytical procedures. These factors must be considered when evaluating results in patients. Submitted on July 21, 1958