Evaluation of Acute Exogenous Hypoxia Impact on the Fraction of Exhaled Nitric Oxide in Healthy Males.

INTRODUCTION Exogenous hypoxia increases ventilation and contracts the pulmonary vessels. Whether those factors change the values of nitric oxide in exhaled air has not yet been evaluated. OBJECTIVE To examine the effect of exogenous normobaric hypoxia on the values of the fraction of nitric oxide in exhaled breath (FeNO). Subjects аnd Methods: Twenty healthy non-smoker males at mean age of 25.4 (SD = 3.7) were tested. The basal FeNO values were compared with those at 7 min. and 15 min. after introducing into the hypoxic environment (hypoxic tent), imitating atmospheric air with oxygen concentration corresponding to 3200 m above sea level. Exhaled breath temperature was measured at baseline and at 10-12 min. of the hypoxic exposition. Heart rate and oxygen saturation were registered by pulse-oximetry. RESULTS All the subjects had FeNO values in the reference range. The mean baseline value was 14.0 ± 3.2 ppb, and in hypoxic conditions - 15.5 ± 3.8 ppb (7 min.) and 15.3 ± 3.6 ppb (15 min.), respectively, as the elevation is statistically significant (p = 0.011 and p = 0.008). The values of exhaled breath temperature were 33.79 ± 1.55°С and 33.87 ± 1.83°С (p = 0.70) at baseline and in hypoxic conditions, respectively. Baseline oxygen saturation in all subjects was higher than that, measured in hypoxia (96.93 ± 1.29% vs. 94.27 ± 2.53%; p < 0.001). CONCLUSIONS Exogenous hypoxia leads to an increase of FeNO values, but does not affect the exhaled breath temperature.