Nitric oxide (NO) in expired air at rest and during exercise

Abstract

Nitric oxide (NO) was analysed in expired air from 27 healthy human subjects. At rest the NO concentration was 10.5 +/- 0.9 ng 1-1 (mean +/- SEM) corresponding to 8.6 +/- 0.7 parts per billion (ppb). The expired NO concentration did not change when the subjects were switched from breathing NO-free tank gas to room air which contained 7.7 ng l-1 NO. Repeated measurements of expired NO with an interval of 1 day showed a mean variation of 2.2 +/- 0.7 ng l-1 NO. The NO concentration in the first portion in the expired tidal volume (44%) was insignificantly higher than in the latter expired portion, 6.9 +/- 1.9 vs. 5.1 +/- 1.0 ng l-1 (n = 5). During moderately heavy exercise on an ergometer bicycle (90 W for women, n = 4, 150 W for men, n = 4) the expired concentration of NO decreased, however because of increased minute ventilation, the expired amount of NO almost doubled (from 111 +/- 12 to 209 +/- 30 ng min-1). The source of the expired NO is not clear and both the airways and the pulmonary circulation may contribute.

Nitric oxide and exercise in the horse.

“…Exercise increased VNO in man (Persson et al 1993;Bauer et al 1994;Trolin et al 1994) and in the horses in the present study. Persson et al (1993) Bauer et al 1994).…”

“…In sheep, inhaled NO does not appear to affect pulmonary vascular tone, although NW-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NOS, induced vasoconstriction and an increase in PAP both at rest and during exercise (Kane et al 1994;Koizumi, Gupta, Bannerjee & Newman, 1994). Several studies have reported an increase in the production rate of NO (VO) in exhaled air during exercise (Persson, Wiklund & Gustafsson, 1993;Bauer, Wald, Doran & Soda, 1994;Iwamoto, Pendergast, Suzuki & Krasney, 1994;Trolin, Anden & Hedenstierna, 1994). Exhaled NO is formed by many different cell types but the exact contribution of each to the exhaled concentration is uncertain.…”

Reduced production of nitric oxide during haemodialysis

“…13 Nevertheless, the level of NO during exhalation differs in various pathophysiologic conditions; for examples, it is increased in patients with asthma, 23,24 bronchiectasis, 25 systemic lupus erythematosus, 26 and liver cirrhosis. 27,28 NO levels were also found to increase with exercise, 29,30 during the mid menstrual cycle in women, 31 and during pregnancy. 32 Conversely, NO was reduced with ethanol ingestion.…”

Nitric oxide in exhaled air

“…The much larger NO excretion in the upper compared to the lower airways is even more clearly apparent if one compares the actual amounts of NO released into different parts of the airways per time unit. Total NO release in the entire normal lower airways as measured in exhaled air of adults is less than 5 nmol·min -1 at rest [13,27]. This is less than the excretion from the paranasal sinuses [13].…”