Altitude-induced central sleep apnea does not affect mean sleep oxygen saturation in young healthy males

At high altitudes, periodic breathing (PB) can occur during sleep in healthy individuals. PB is characterized by a cyclical ventilatory pattern that alternates between central sleep apnea and brief episodes of hyperventilation. The aim of this study was to evaluate the effect of periodic breathing on sleep blood oxygen saturation ([Formula: see text]). Thirty-six healthy male subjects (median [IQR] age: 26 [24-28] yr old, median [IQR] body mass index: 22.7 [21.1-23.8] kg/m²) underwent a polysomnography at a simulated altitude of 3,500 m ([Formula: see text]: 13%). Correlations were sought between the apnea-hypopnea index (AHI), oxygen desaturation index (ODI), percentage of sleep time spent in PB (PB), and mean [Formula: see text] throughout the entire sleep period by calculating the Spearman's rank correlation test. We identified 20 participants who had experienced at least 3 min of periodic breathing adjacent to at least 3 min of regular breathing (RB). We compared the mean [Formula: see text] between the two respiratory patterns using Wilcoxon signed-rank test. At simulated altitude, the subjects spent a median [IQR] of 43.9 [12.5-79.1]% of sleep time in PB. The median [IQR] AHI was 77.3 [31.4-127.5]/h, and the median [IQR] ODI was 82.6 [52.6-134.0]/h. Median awake and asleep [Formula: see text] were 75.4 [72.0-77.2]% and 68.5 [66.4-72.5]%, respectively. We found no within-subject difference in mean [Formula: see text] between RB and PB periods (median [IQR] RB vs. PB: 67.2% [63.8%-74.8%] vs. 67.5% [64.5%-73.9%]; P = 0.43). No significant correlation was found between the mean sleep [Formula: see text] and AHI (n = 36, rs = -0.19, P = 0.26), ODI (n = 36, rs = -0.23, P = 0.18) or PB (n = 36, rs = -0.07, P = 0.67). Awake [Formula: see text] was correlated with mean [Formula: see text] during sleep (n = 36, rs = 0.55, P = 0.001). Periodic breathing per se does not have a detrimental effect on mean [Formula: see text] in young healthy males. Correlation between awake [Formula: see text] and sleep [Formula: see text] suggests that sleep [Formula: see text] at high altitude is primarily determined by baseline oxygen saturation rather than the respiratory pattern developed during sleep.NEW & NOTEWORTHY Periodic breathing, which occurs during sleep at altitude, causes an oscillation between central apneas and periods of hyperventilation. The overall impact of this breathing pattern on blood oxygen saturation ([Formula: see text]) remains a topic of debate. We compared the mean [Formula: see text] between periods of periodic breathing and periods of regular breathing for the same individual. The results suggest that periodic breathing does not affect mean sleep [Formula: see text].