Abstract de conférence
Résumé : Future space missions may expose astronauts to hypobaric hypoxic conditions akin to high altitudes,intensifying existing concerns over astronauts’ sleep disturbances. The Concordia station in Antarctica,situated at an equivalent altitude of 3800 meters, offers an ideal setting for such investigations. Previous research in Concordia showed a high incidence of periodic breathing and central apnea. Whilepolysomnography is the standard for diagnosing sleep apnea, it may disturb normal sleep, it is expensive, and requires expertise. Recent studies have explored alternative diagnostic methods, including heartrate variability (HRV) during breathing cycles, showing promise in identifying sleep apnea, especiallyin cases of moderate to severe obstructive sleep apnea where lower respiratory HRV is observed duringdaytime. This study aims to assess the applicability of HRV in investigating sleep disturbances inducedby hypobaric hypoxia.Our study involved 9 male crew members assigned to a 12-month mission at the Concordia station.Electrocardiography data (500 Hz) was collected three months before the mission and in the 10th month onsite. Participants followed a breathing protocol consisting of 10 cycles of 10-second breathing. HRVwas measured as ∆HR, the difference between maximum and minimum heart rates within a respiratorycycle.We examined the changes in ∆HR between baseline and the 10th month at Concordia, and againstboth sea-level participants and obstructive sleep apnea patients. Wilcoxon signed rank test was usedfor paired comparisons and Mann-Whitney test for unpaired comparisons, with a significance level ofp = 0.05.Although not significant (p = 0.07), 8 out of 9 subjects experienced a decrease in ∆HR after tenmonths at Concordia from (14.85[12.70; 21.75] bpm) to (12.47[10.10; 18.61] bpm). The sole participantexhibiting an increase in ∆HR also underwent substantial weight loss (12 kg), potentially influencing theresults. Interestingly, even after 10 months in high altitude, participants’ ∆HR remained higher thanthat of sleep apnea patients study (8.30[4.79; 10.84] bpm, p = 0.018) but similar to that of a control groupat a sea-level Antarctic station (16.54[11.86; 22.31] bpm, p = 0.275).Patients with obstructive sleep apnea have significantly lower ∆HR than subjects exposed to prolongedhigh-altitude with a high incidence of central apnea. We hypothesize that ∆HR is influenced by sleepdisorders possibly due to an increase in sympathovagal balance. However, future studies should assessthe correlations between ∆HR and other factors.

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