Effect Of Acetazolamide Versus Heat Acclimation On Oxygen Saturation During Sleep At Altitude

Abstract

Reduced oxygen at high altitude can alter breathing at night which can disrupt sleep. Acetazolamide (AZ) has been shown to augment breathing and oxygen saturation (SpO2) during sleep. However, it is unclear whether heat acclimation (HA), which has been suggested to have beneficial effects in hypoxia, may provide benefits similar to AZ. PURPOSE: To determine if there is a difference in average SpO2 (avgO2), time below 88% SpO2 (TBL88), and average pulse rate (PR) between treatments with AZ verses HA. METHODS: Seventeen unacclimatized healthy men (age: 22 ± 4 years; mass: 75 ± 12 kg; height: 172 ± 8 cm; body fat: 22 ± 6%) participated in at least one of two (N = 6 completed both) 30-hour altitude studies: Study 1) AZ (250 mg twice/day for three days) vs placebo or Study 2) pre-HA altitude exposure, followed by an 8-day exercise-HA protocol (treadmill walking: 120 min, 3.1 mph 2% grade, 40°C, 40% RH), and then a post-HA altitude exposure. Both studies were identical in regards to altitude (3,500 m), ascent rate, exposure time, and sleep assessment. For analysis, PL and pre-HA acted as the control conditions (CON) and AZ and post-HA as the experimental conditions (EXP). AvgO2, TBL88, and average PR were recorded during sleep via wrist pulse oximeter. A linear mixed model with subjects as a random effect was used to compare treatments (AZ and HA), and conditions (CON and EXP) with total sleep time as a covariate for TBL88. RESULTS: There was a significant interaction between the condition and treatment-type for avgO2 (p < .001) and TBL88 (p < .001) during sleep, but no interaction was found for average PR (p = .49). Pairwise comparisons were performed for the former two variables within each study treatment. AvgO2 was greater in the AZ treatment (difference = 5.7%; 95% C.I. [4.2, 7.2]), and a non-significant increase in avgO2 was found post-HA (difference = 0.9%; 95% C.I. [-0.3, 2.2]). Additionally, TBL88 was reduced in the AZ treatment (difference = -207.7 min; 95% C.I. [-283.2, -132.2]), while there was a non-significant increase in TBL88 post-HA. PR was higher in CON (72 bpm) than EXP (69 bpm). CONCLUSION: Our data confirms AZ increases SpO2 during sleep at altitude, however, we were unable to observe a similar improvement in oxygen saturation after HA. Supported by USAMRDC; author views not official US Army or DoD policy.