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

Abstract

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. 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)). PE(NOcorr) was reduced from 1.47 (1.21, 1.73) millipascal (mPa) at baseline to 1.11 (0.87, 1.34) mPa 5 mins after exercise at 2800 m and from 1.54 (1.24, 1.84) to 1.04 (0.87, 1.22) mPa 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. Exercise at 2800 m induces a similar acute reduction in exhaled nitric oxide concentration as compared with 180 m in healthy subjects.