Differences in nitric oxide airway diffusion after maximum oxygen uptake test in asthmatic and nonasthmatic elite junior cross-country skiers

Abstract

Asthma is common in cross-country skiers and is often treated with β₂-agonists and inhaled corticosteroids (ICS). Exhaled nitric oxide (NO) is often used to guide ICS treatment in asthma. This study investigated the change in pulmonary NO dynamics before and after a maximum oxygen uptake (V'_{O2 max}) test. An extended NO analysis was performed among Swedish elite junior cross-country skiers (n=25), with and without declared asthma, before and after a V'_{O2 max} test using roller skis. Asthma was declared by six boys and two girls among whom five occasionally used ICSs. There were no differences in baseline NO parameters between those with and without declared asthma. The median (interquartile range) diffusion capacity over airway wall (D _awNO) was 21 (17-25) mL·s^-1, which is much increased for this age group. After the V'_{O2 max} test, there were statistically significant differences from the baseline fraction of exhaled NO (F _ENO50 ), NO flux from airways, D _awNO and alveolar NO values; but not in the NO content in airway wall (C _awNO) for all subjects together as one group. However, in the asthma group, differences were only seen in F _ENO50 and C _awNO. Interestingly, a majority of the subjects had an increase in the D _awNO. An increase in D _awNO has been found with allergic asthma together with elevated C _awNO. The skiers did not have elevated C _awNO, which indicates an absence of inflammation in the airway wall. Modelling of lung NO production clearly shows that the asthma among our skiers is distinct from the allergic asthma in nonathletes.