LAUSR

Many popular tourist destinations are at high-altitude. Visitors commonly report poor sleep quality during the first few nights after arriving, but some do not resolve over time and daytime symptoms may develop that require medical attention. A previously healthy 76-year-old American man presented with progressive fatigue and frequent nocturnal awakenings to a clinic in Bogota, Columbia (altitude 2640 meters), where he had been living for eighteen months during the COVID-19 pandemic lockdown due to limited ability to travel. An arterial blood gas on room air revealed hypocapnia with a partial pressure of CO2 of 25 mmHg. A polysomnography (PSG) performed in Bogota demonstrated an apnea-hypopnea index (AHI) of 98 events/hour consisting of predominately central as well as obstructive respiratory disturbances (Figure 1). After a titration study, he was placed on treatment with continuous positive airway pressure (CPAP) at 10 cmH2O along with oxygen 1 L/min, but he had difficulty acclimating to treatment. The patient presented to our institution two months after returning to the USA with significantly improved symptoms despite remaining off CPAP. Repeat PSG revealed a substantial reduction in the AHI at 15 events/hour consisting of only central respiratory disturbances in the supine position during transitional N1/N2 sleep (Figure 2). Positional therapy was recommended. A repeat home sleep study performed three months later to reassess disease severity during non-supine sleep showed resolution of respiratory disturbances (Figure 3). High-altitude periodic breathing is a common phenomenon, characterized by alternating periods of absent respiratory efforts with periods of hyperventilation without another etiology (1, 2). It occurs due to the interaction of hypocapnia and increased loop-gain (2). Central sleep apnea (CSA) is considered a disorder only when associated with symptoms, not simply due to an elevated central apnea index (3). The more rapid ascent and the higher the altitude, the greater risk of developing periodic breathing. Descending to a lower altitude will often resolve apnea after few days but the phenomenon can persist for up to months (2, 4) as our patient. CSA develops commonly upon ascent to high altitude. When feasible, symptomatic patients should be encouraged to descend to a lower altitude.