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

Abstract

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 (FENO) 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). FENO measurements were corrected for altitude gas density effects and converted to partial pressure of NO (PENOcorr).

Results: PENOcorr 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 PENOcorr between exercise at 2800 m and 180 m, and PENOcorr was normalized within 20 mins.