Respiratory acclimatization and psychomotor performance after rapid ascent and during 3 weeks at 3100 m. A prospective cohort study in healthy

Background The acclimatization to high altitudes over several weeks is not extensively studied. Repeated physiological assessments were performed in healthy lowlanders staying at 3100m for 3 weeks. We hypothesized that over the course of 3 weeks, the arterial oxygen saturation (SpO2) improves and has favorable effects on psychomotor vigilance, postural control, and sleep.

16 healthy volunteers (23-33y) underwent sleep studies during 1 night in Bishkek (760m), and during nights 1, 8 and 22 at Too-Ashu (3100m), Kyrgyzstan. The day after, reaction time (psychomotor vigilance test reaction time test, PVT) and postural control (center of gravity path length on balance board [COPL]) were assessed.

Compared to 760m, mean nocturnal SpO2 dropped in the first night at 3100m from mean±SD 94.8±1.9% to 86.3±2.9% and recovered partially to 89.8±1.5% after 3 weeks (P<0.05 both comparisons to 760m). Corresponding median (quartiles) oxygen desaturation indices were 1.0/h(0.3;2.2), 6.5/h(4.5;12.1) and 6.4/h(4.2;11.1) time in bed (P<0.05 both comparisons to 760m). Median (quartiles) reaction times were 226ms(212;231), 236ms(210;259) and 228ms(212;246), P=NS, all comparisons. COPL worsened from 25.1±4.1cm to 27.1±4.1cm (P<0.05) and 26.4±3.7cm (P=NS compared to 760m).

In healthy lowlanders staying at 3100m, nocturnal SpO2 increased over 3 weeks after an initial drop but did not reach 760m baseline values. Postural control was impaired in the first week of acute exposure to high altitude despite improvements in hypoxemia. Altitude exposure had no effect on reaction time. Thus, acute and prolonged exposure to hypobaric hypoxia has differential effects on oxygenation, control of breathing, postural control and reaction time. Competing Interest Statement The authors have declared no competing interest. Clinical Trial NCT02451020 Funding Statement The study was supported by the Swiss National Science Foundation (172980) and Lunge Zurich. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics Committee of the National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan gave ethical approval for this work (01-8/405). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All data produced in the present study are available upon reasonable request to the authors.