Exhaled nitric oxide after high‐intensity exercise at 2800 m altitude

Summary Background Nitric oxide ( NO ) concentration in exhaled gas is a marker of some inflammatory processes in the lung, and endogenous NO plays a role in the physiological responses to exercise and altitude. The aim of this study was to compare changes in exhaled NO concentration 5–60 mins after high‐intensity exercise at 2800 m and at 180 m altitude. Methods Twenty trained healthy volunteers (12 men), aged 19–28 years, were included in this open, crossover study. Subjects performed two exercise tests at different altitudes, 2800 m and 180 m, in a randomized order. The fraction of NO in exhaled gas ( FE NO ) was measured 5 mins before and 5–60 mins after 8 mins of running on a treadmill at a heart rate ( HR ) of 90% of peak HR . Peak HR was assessed during a pretest at 180 m. Ambient temperature was 20·1°C ( SD  = 1·2) and relative humidity 40·2% ( SD  = 3·2). FE NO measurements were corrected for altitude gas density effects and converted to partial pressure of NO ( PE NOcorr ). Results PE NOcorr was reduced from 1·47 (1·21, 1·73) millipascal (mPa) at baseline to 1·11 (0·87, 1·34) mP a 5 mins after exercise at 2800 m and from 1·54 (1·24, 1·84) to 1·04 (0·87, 1·22) mP a 5 mins after exercise at 180 m. There was no difference in PE NOcorr between exercise at 2800 m and 180 m, and PE NOcorr was normalized within 20 mins. Conclusions Exercise at 2800 m induces a similar acute reduction in exhaled nitric oxide concentration as compared with 180 m in healthy subjects.