Acetazolamide effect on high altitude periodic breathing during sleep. The HIGHCARE Alps project

Abstract

Purpose: Periodic breathing (PB) is frequently reported at night at high altitude. We have previously shown that this respiratory pattern is less frequent in female subjects. Little is known about gender differences on the acetazolamide effect on this phenomenon. Aim of our randomized, double blind study was to explore whether acetazolamide may influence PB during sleep in males and females subjects under acute exposure to high altitude hypoxia. Methods: All subjects (43 healthy subjects, 22 male) participating in the HIGH altitude Cardiovascular Research Alps project were randomized to acetazolamide (250 mg x2/die) (ACZ) or placebo (PL). During the expedition we performed nocturnal cardiorespiratory polysomnography during the second night at Capanna Margherita Hut 4554 m above SL). Results: During night at 4554 m apnea-hypopnea index (AHI) was 40.87+ 27.83 events/h in male PL, 3.77+ 3.8 events/h in male ACZ, 7.33+3.99 events/h in female PL and 2.92+ 3.52 events/h in female ACZ. The mean SaO2 during the night is significantly higher both in males than in females with ACZ as compared with PL groups (p<0.001). Additionally min SaO2 is significantly higher in females ACZ vs females and males PL; conversely min SaO2 is significantly higher in males ACZ vs females PL (p<0.05), but no statistically significant difference is observed between min SaO2 in males ACZ and males PL (see Table). View this table: Conclusions: We previously showed that at high altitude PB at night affects more frequently males than females. The present data confirm AHI differences between males and females. Moreover the present study suggests that ACZ significantly reduces AHI in males increasing also the mean SaO2 during the night, but not the min SaO2. In females subjects ACZ reduces AHI without statistically significance, but increases significantly both the mean and min SaO2.In conclusion, our data suggest that the determinants of periodic breathing at high altitude are complex and not only linked to hypoxia, but also to the CO2 level and in particular to the gender related central and peripheral chemosensitivity.