Mg. Persson et al., ENDOGENOUS NITRIC-OXIDE IN SINGLE EXHALATIONS AND THE CHANGE DURING EXERCISE, The American review of respiratory disease, 148(5), 1993, pp. 1210-1214
The concentrations of endogenous nitric oxide (NO) and CO2 were measur
ed in exhaled air from healthy humans. During a single exhalation, NO
concentrations peaked when the CO2 level reached its plateau. However,
whereas CO2 levels remained at a plateau throughout the exhalation, N
O concentrations declined after having peaked. After breathholding (5
to 60 s) NO peaked at a higher level than du ring normal breathing. Ni
tric oxide concentrations in exhaled air decreased during physical exe
rcise (50 to 100 W). However, taking the increased ventilatory minute
volume into account, excretion of NO markedly increased during exercis
e. The data are compatible with the hypothesis that the NO detected in
exhaled air is formed preferentially in the terminal and respiratory
bronchioles, and they suggest increased production of NO into exhaled
air during exercise and during hyperventilation at rest.