Influence Of Acetazolamide On The Physiological And Perceptual Responses To Steady-state Exercise At Altitude

Abstract

Acetazolamide (AZ) is a common prophylactic for acute mountain sickness (AMS), particularly during rapid ascent to moderate or high altitudes. However, its diuretic effect could have a negative impact on physiological responses during steady-state exercise; these potential influences are poorly understood. PURPOSE: To evaluate the impact of AZ on heart rate (HR), rate of perceived exertion (RPE), and oxygen saturation (SaO2) during steady-state treadmill walking after ~24 hours exposure to hypobaric hypoxia equivalent to 3500 m altitude. METHODS: After completing three sea level familiarization trials, six men (Age: 22.2 ± 3.2 yr; Weight: 77.5 ± 11.5 kg; Height: 176.2 ± 7.1 cm; SL VO2peak: 50.8 ± 6.5 ml·kg-1·min-1) completed two 30 hr altitude exposures (AZ and placebo, single-blind randomized crossover design) in a hypobaric chamber equivalent to ~3500 m. After ~24 hr of exposure, volunteers completed exercise testing consisting of 15 min of steady-state treadmill exercise at 40-45% sea level VO2peak. HR & SaO2 were recorded at baseline and at minutes 5, 10, and 15 of exercise. RPE was recorded at baseline and at minute 15 of exercise. RESULTS: There were no significant differences between AZ and placebo for post-exercise HR (AZ: 141 ± 11 bpm [mean ± SD] vs. Placebo: 145 ± 12 bpm; p > 0.05) or RPE (AZ: 9.5 (6-13) [median (range)] vs. Placebo: 9.0 (7-14); p > 0.05). SaO2 was significantly higher in the AZ trial (AZ: 86 ± 3% vs. Placebo: 81 ± 4%, p < 0.01). Furthermore, the extent (delta) of desaturation from pre- to post- steady-state exercise was less in the AZ trial compared to the placebo trial (AZ: -5 ± 3% vs. Placebo: -7 ± 1%; p < 0.05). CONCLUSIONS: Our results suggest that AZ does not negatively impact physiological and perceptual responses during steady-state exercise. Indeed, AZ may be beneficial by helping to maintain oxygen saturation during steady-state exercise in hypobaric hypoxia. Funded by USAMRMC; author views not official US Army or DOD policy.