Exhaled nitric oxide level during and after heavy exercise in athletes with exercise-induced hypoxaemia

Endogenous nitric oxide (NO) is an important mediator of vasodilatation, bronchodilatation and lung inflammation. We hypothesised that the exhaled NO level may be modified in some endurance-trained athletes during and after intense exercise. Nine athletes with exercise-induced hypoxaemia (EIH), 12 athletes without EIH and 10 untrained subjects exercised for 15 min at 90% maximal oxygen consumption ((V) over dot O(2)max). Exhaled NO was measured during exercise, and after 1 h and 22 h of recovery. Exhaled NO concentration (C-NO) decreased significantly during exercise in all subjects and returned to basal values after 1 h of recovery with no further modification. Exhaled NO output ((V) over dot (NO)) rose significantly during exercise, rapidly dropped down following exercise and was similar to resting values after 1 h and 22 h of recovery. The results also showed that CNO and (V) over dot (NO) were significantly lower in the athletes with EIH in comparison with the untrained subjects ((V) over dot (NO) was 5.32 +/- 0.77 nmol/min versus 3.61 +/- 0.72 nmol/min at rest, 18.52 +/- 1.50 nmol/min versus 15.00 +/- 2.06 nmol/min during heavy exercise, and 5.52 +/- 1.04 nmol/min versus 3.79 +/- 0.76 nmol/min after 22 h recovery, in untrained subjects and EIH athletes, respectively). These findings do not confirm the hypothesis of pulmonary inflammation associated with EIH. However, potential NO epithelial down-regulation may occur and contribute to the development of gas exchange abnormality in some endurance-trained athletes.