Chemiluminescent measurements of nitric oxide pulmonary diffusing capacityand alveolar production in humans

Measurements of nitric oxide (NO) pulmonary diffusing capacity (DLNO) multi plied by alveolar NO partial pressure (PA(NO)) provide values for alveolar NO production ((V) over dotA(NO)). We evaluated applying a rapidly respondi ng chemiluminescent NO analyzer to measure DLNO during a single, constant e xhalation (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 measure d NO back pressure, DexNO in nine healthy subjects equaled 125 +/- 29 (SD) ml.min(-1).mmHg(-1) and Drb(NO) equaled 122 +/- 26 ml.min(-1).mmHg(-1). The se values were 4.7 +/- 0.6 and 4.6 +/- 0.6 times greater, respectively, tha n the subject's single-breath carbon monoxide diffusing capacity (Dsb(CO)). Coefficients of variation were similar to previously reported breath-holdi ng, single-breath measurements of DsbCO. PANO measured in seven of the subj ects equaled 1.8 +/- 0.7 mmHg x 10(-6) and resulted in (V) over dot A(NO) o f 0.21 +/- 0.06 mul/min using Dex(NO) and 0.20 +/- 0.6 mul/min with Drb(NO) . Dex(NO) remained constant at end-expiratory oxygen tensions varied from 4 2 to 682 Torr. Decreases in lung volume resulted in falls of Dex(NO) and Dr b(NO) similar to the reported effect of volume changes on Dsb(CO). These da ta show that rapidly responding chemiluminescent NO analyzers provide repro ducible measurements of DLNO using single exhalations or rebreathing suitab le for measuring (V) over dot A(NO).