1. Acute mountain sickness is not repeatable across two 12-hour normobaric hypoxia exposures.
- Author
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MacInnis MJ, Koch S, MacLeod KE, Carter EA, Jain R, Koehle MS, and Rupert JL
- Subjects
- Acclimatization, Adolescent, Blood Pressure, Case-Control Studies, Female, Heart Rate, Humans, Male, Nitric Oxide metabolism, Oxygen metabolism, Young Adult, Altitude Sickness physiopathology, Hypoxia physiopathology
- Abstract
Objective: The purposes of this experiment were to determine the repeatability of acute mountain sickness (AMS), AMS symptoms, and physiological responses across 2 identical hypoxic exposures., Methods: Subjects (n = 25) spent 3 nights at simulated altitude in a normobaric hypoxia chamber: twice at a partial pressure of inspired oxygen (PIO2) of 90mmHg (4000 m equivalent; "hypoxia") and once at a PIO2 of 132 mmHg (1000 m equivalent; "sham") with 14 or more days between exposures. The following variables were measured at hours 0 and 12 of each exposure: AMS severity (ie, Lake Louise score [LLS]), AMS incidence (LLS ≥3), heart rate, oxygen saturation, blood pressure, and the fraction of exhaled nitric oxide. Oxygen saturation and heart rate were also measured while subjects slept., Results: The incidence of AMS was not statistically different between the 2 exposures (84% vs 56%, P > .05), but the severity of AMS (ie, LLS) was significantly lower on the second hypoxic exposure (mean [SD], 3.1 [1.8]) relative to the first hypoxic exposure (4.8 [2.3]; P < .001). Headache was the only AMS symptom to have a significantly greater severity on both hypoxic exposures (relative to the sham exposure, P < .05). Physiological variables were moderately to strongly repeatable (intraclass correlation range 0.39 to 0.86) but were not associated with AMS susceptibility (P > .05)., Conclusions: The LLS was not repeatable across 2 identical hypoxic exposures. Increased familiarity with the environment (not acclimation) could explain the reduced AMS severity on the second hypoxic exposure. Headache was the most reliable AMS symptom., (Copyright © 2014 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2014
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