Nocturnal periodic breathing and arterial oxygen desaturation in acute mountain sickness

Abstract

The objective of this case-control study was to investigate the relationship between periodic breathing (PB) and acute mountain sickness (AMS). Nine volunteers, healthy lowlanders between the age of 20 and 36 years stayed at a simulated altitude of 3700 m (485 Torr) for 24 h in a hypobaric chamber. A sleep study was carried out for more than 6 h. Arterial oxygen saturation (SaO 2 ) was monitored by finger oximetry on all subjects. PB was determined by a polysomnography (EEG, EOG, thoracic movement) in six subjects and was indirectly measured by studying the cyclic change of SaO 2 in three other subjects. The severity of AMS was assessed with the Environmental Symptoms Questionnaire. All subjects showed lower SaO 2 during sleep than when awake (65.0 ± 6.4% versus 72.6 ± 6.4%, p < 0.01), and symptoms of AMS were more intense the next morning. PB was observed in eight of the nine subjects; however, the time spent in PB (%PB) ranged from 0% to 57.8%. There was a positive correlation between %PB and stage 1 sleep, suggesting an important role of PB in poor sleep quality at high altitude. Percent PB, however, was not significantly correlated with the degree of sleep desaturation, the severity of AMS, and ventilatory responses to hypoxia and hypercapnia. These results suggest that PB may not be a critical factor for sleep desaturation and in the development of AMS for high-altitude newcomers.