title: SpO2and Heart Rate During a Real Hike at Altitude Are Significantly Different than at Its Simulation in Normobaric Hypoxia.
abstract: Rationale:Exposures to simulated altitude (normobaric hypoxia, NH) are frequently used in preparation for mountaineering activities at real altitude (hypobaric hypoxia, HH). However, physiological responses to exercise in NH and HH may differ. Unfortunately clinically useful information on such differences is largely lacking. This study therefore compared exercise responses between a simulated hike on a treadmill in NH and a similar field hike in HH.Methods:Six subjects (four men) participated in two trials, one in a NH chamber and a second in HH at an altitude of 4,205 m on the mountain Mauna Kea. Subjects hiked in each setting for 7 h including breaks. In NH, hiking was simulated by walking on a treadmill. To achieve maximal similarity between hikes, subjects used the same nutrition, clothes, and gear weight. Measurements of peripheral oxygen saturation (SpO2), heart rate (HR) and barometrical pressure (PB)/inspired oxygen fraction (FiO2) were taken every 15 min. Acute mountain sickness (AMS) symptoms were assessed using the Lake-Louise-Score at altitudes of 2,800, 3,500, and 4,200 m.Results:Mean SpO2values of 85.8% in NH were significantly higher compared to those of 80.2% in HH (p= 0.027). Mean HR values of 103 bpm in NH were significantly lower than those of 121 bpm in HH (p= 0.029). AMS scores did not differ significantly between the two conditions.Conclusion:Physiological responses to exercise recorded in NH are different from those provoked by HH. These findings are of clinical importance for subjects using simulated altitude to prepare for activity at real altitude.Trial registration:Registration at DRKS. (Approval No. 359/12, Trial No. DRKS00005241).
authors.affiliation: Department of Sport Science, University InnsbruckInnsbruck, Austria; Department for Hypoxia Research, Hermann Buhl Institute for Hypoxia and Sleep Medicine ResearchBad Aibling, Germany; Division Sports Medicine and Rehabilitation, Department of Medicine, University UlmUlm, Germany.
authors.forename: Nikolaus C
authors.initials: NC
authors.lastname: Netzer
authors.affiliation: Department for Hypoxia Research, Hermann Buhl Institute for Hypoxia and Sleep Medicine Research Bad Aibling, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Rausch
authors.affiliation: Department of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA.
authors.forename: Arn H
authors.initials: AH
authors.lastname: Eliasson
authors.affiliation: Department of Sport Science, University Innsbruck Innsbruck, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.affiliation: Department of Sport Science, University Innsbruck Innsbruck, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Friess
authors.affiliation: Department of Sport Science, University Innsbruck Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
authors.affiliation: Department for Hypoxia Research, Hermann Buhl Institute for Hypoxia and Sleep Medicine Research Bad Aibling, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Pramsohler
keywords: altitude; heart rate; hypobaric hypoxia; normobaric hypoxia; oxygen saturation