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

At high-altitude, 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 SpO2. 36 healthy males subjects (median-age:26[24-28]years old, median BMI:22.7[21.1-23.8]Kg/m2) underwent a polysomnography at a simulated altitude of 3,500 meters(FiO2:13%). Correlations were sought between the Apnea-Hypopnea Index(AHI), Oxygen Desaturation Index(ODI), percentage of total sleep time spent in PB, and mean SpO2 throughout the entire sleep period by calculating the Spearman's rank correlation test. We identified 20 participants who had experienced at least 3 minutes of PB adjacent to at least 3 minutes of regular breathing(RB). We compared the mean SpO2 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 in PB and the median-AHI was 77.3[31.4-127.5]/h. Median awake and asleep SpO2 were 75.4[24-28]% and 68.5[66.4-72.5]% respectively. We found no within subject difference in SpO2 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 SpO2 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 SpO2 was correlated with mean SpO2 during sleep(n=36,rs=0.55;p=0.001). PB per se does not have a detrimental effect on mean SpO2 in young healthy males. Correlation between awake and sleep SpO2, suggests that sleep SpO2 at high-altitude is primarily determined by baseline oxygen saturation rather than the respiratory pattern developed during sleep.