MEASUREMENT OF EXHALED NITRIC-OXIDE IN HEALTHY-SUBJECTS

BACKGROUND: Endogenously synthesized nitric oxide (NO) is present in e xhaled air and its analysis could be used as a tool to monitor inflamm atory airway diseases. The objective of the present study was to devel op the methodology for the measurement of exhaled NO and to obtain ref erence values in a group of healthy subjects. SUBJECTS AND METHOD: Exh aled NO was measured in 40 healthy subjects and 22 asthmatic patients using a single breath manoeuvre and a chemiluminescence analyzer. Comp arisons of exhaled NO while breathing both, room air and medical air, were performed in 20 subjects. In seven asthmatic patients we evaluate d the effect of an inhibitor of NO-synthesis (L-NAME). RESULTS: Mean ( SD) exhaled NO in healthy subjects was 18 (13) parts per billion (ppb) . Intraindividual variability was 6.5 (6.5%). The concentration of exh aled NO could be overestimated when environmental NO was high (> 80 pp b). Smokers showed lower levels than nonsmokers (10 [7] vs 22 [13] ppb , respectively; p < 0.005), whereas asthmatic patients showed higher e xhaled NO levels (62 [31] ppb; p < 0.001). In these patients nebulizat ion of L-NAME induced a progressive fall in exhaled NO (maximal decrea se, -68 [15%]; p < 0.01). CONCLUSIONS: The measurement of NO concentra tion in exhaled air is reproducible, not influenced by the usual level s of environmental NO, and sensible enough to detect changes induced b y the administration of a specific inhibitor. Exhaled NO concentration decreases in smokers and increases in asthmatics.