Effects of acute hypoxic provocation on the autonomic nervous system in 'healthy' young smokers, measured by heart rate variability.

AIM: The aim of this study was to compare the activity of the autonomic nervous system (ANS) using heart rate variability (HRV) in 'healthy' young smokers and non-smokers before, during and after exogenous hypoxic provocation. METHODS: Twenty-one healthy non-smoking males aged 28.0 ± 7.4 years (mean ± SD) and 14 'healthy' smoking males aged 28.1 ± 4.3 years with 9.2 ± 5.6 pack-years were subjected to one-hour hypoxic exposure (FiO2 = 12.3 ± 1.5%) via a hypoxicator. HRV data was derived via Kubios HRV, Finland software by analysing the pre-hypoxic, hypoxic and post-hypoxic periods. RESULTS: Standard deviation of the intervals between normal beats (SDNN) was higher in the non-smokers in the pre-hypoxic period (62.0 ± 32.1 vs 40.3 ± 16.2 ms, p = 0.013) but not in the hypoxic period (75.7 ± 34.8 vs 57.9 ± 18.3 ms, p = 0.167). When comparing intra-group HRV changes, shifting from hypoxic to normoxic conditions, there was an increase in the mean square root of successive R-R interval differences (RMSSD) (65.9 ± 40.2 vs 75.1 ± 45.9 ms, p = 0.011), but these changes were observed in only the group of non-smokers. CONCLUSIONS: Smoking probably impairs autonomic regulation in healthy young males and may lead to decreased HRV, even before subjective clinical signs and symptoms appear.

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°Ð¡ and 33.87 ± 1.83°Ð¡ (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.