Chemiluminescent measurements of nitric oxide pulmonary diffusing capacity and alveolar production in humans

Measurements of nitric oxide (NO) pulmonary diffusing capacity (DL(NO)) multiplied by alveolar NO partial pressure (PA(NO)) provide values for alveolar NO production (VA(NO)). We evaluated applying a rapidly responding chemiluminescent NO analyzer to measure DL(NO) during a single, constant exhalation (Dex(NO)) or by rebreathing (Drb(NO)). With the use of an initial inspiration of 5-10 parts/million of NO with a correction for the measured NO back pressure, Dex(NO) in nine healthy subjects equaled 125 +/- 29 (SD) ml x min(-1) x mmHg(-1) and Drb(NO) equaled 122 +/- 26 ml x min(-1) x mmHg(-1). These values were 4.7 +/- 0.6 and 4.6 +/- 0.6 times greater, respectively, than the subject's single-breath carbon monoxide diffusing capacity (Dsb(CO)). Coefficients of variation were similar to previously reported breath-holding, single-breath measurements of Dsb(CO). PA(NO) measured in seven of the subjects equaled 1.8 +/- 0.7 mmHg x 10(-6) and resulted in VA(NO) of 0.21 +/- 0.06 microl/min using Dex(NO) and 0.20 +/- 0.6 microl/min with Drb(NO). Dex(NO) remained constant at end-expiratory oxygen tensions varied from 42 to 682 Torr. Decreases in lung volume resulted in falls of Dex(NO) and Drb(NO) similar to the reported effect of volume changes on Dsb(CO). These data show that rapidly responding chemiluminescent NO analyzers provide reproducible measurements of DL(NO) using single exhalations or rebreathing suitable for measuring VA(NO).