Respiratory Stimulants and Sleep Periodic Breathing at High Altitude

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Abstract
We studied the effects of almitrine, acetazolamide, and placebo on the hypoxic ventilatory response (HVR), sleep periodic breathing, and arterial oxygen saturation (SaO2) in 4 healthy climbers. In a laboratory on Denali (Mt. McKinley) at 4,400 m (PB = 440 mm Hg), we used a double-blind, randomized, three-way crossover design. The HVR was measured during the waking state. Periodic breathing and SAO2% were measured during 3-h sleep studies. Almitrine and acetazolamide both increased SaO2% during sleep, although almitrine increased periodic breathing, whereas acetazolamide decreased periodic breathing. The HVR was doubled with almitrine (p < 0.05), but unchanged with acetazolamide. The HVR was positively related to periodic breathing (p < 0.05). We conclude that periodic breathing during sleep at high altitude is related to the hypoxic ventilatory response, and that acetazolamide is a superior agent to almitrine for ameliorating periodic breathing.