title: Efficacy of residence at moderate versus low altitude on reducing acute mountain sickness in men following rapid ascent to 4300 m.
abstract: To determine if residence at moderate (~2000 m) compared to low (<50 m) altitude reduces acute mountain sickness (AMS) in men during subsequent rapid ascent to a higher altitude. Nine moderate-altitude residents (MAR) and 18 sea-level residents (SLR) completed the Environmental Symptoms Questionnaire (ESQ) at their respective baseline residence and again at 12, 24, 48, and 72 h at 4300 m to assess the severity and prevalence of AMS. AMS cerebral factor score (AMS-C) was calculated from the ESQ at each time point. AMS was judged to be present if AMS-C was ≥0.7. Resting end-tidal CO2 (PETco2) and arterial oxygen saturation (Sao2) were assessed prior to and at 24, 48, and 72 h at 4300 m. Resting venous blood samples were collected prior to and at 72 h at 4300 m to estimate plasma volume (PV) changes. MAR compared to SLR: 1) AMS severity at 4300 was lower (p<0.05) at 12 h (0.50±0.69 vs. 1.48±1.28), 24 h (0.15±0.19 vs. 1.39±1.19), 48 h (0.10±0.18 vs. 1.37±1.49) and 72 h (0.08±0.12 vs. 0.69±0.70); 2) AMS prevalence at 4300 was lower (p<0.05) at 12 h (22% vs. 72%), 24 h (0% vs. 56%), 48 h (0% vs. 56%), and 72 h (0% vs. 45%); 3) resting Sao2 (%) was lower (p<0.05) at baseline (95±1 vs. 99±1) but higher (p<0.05) at 4300 at 24 h (86±2 vs. 81±5), 48 h (88±3 vs. 83±6), and 72 h (88±2 vs. 83±5); and 4) PV (%) did not differ at 72 h at 4300 m in the MAR (4.5±6.7) but was reduced for the SLR (-8.1±10.4). These results suggest that ventilatory and hematological acclimatization acquired while living at moderate altitude, as indicated by a higher resting Sao2 and no reduction in PV during exposure to a higher altitude, is associated with greatly reduced AMS after rapid ascent to high altitude.
authors.affiliation: Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA. janet.staab@us.army.mil
authors.forename: Janet E
authors.initials: JE
authors.lastname: Staab
authors.forename: Beth A
authors.initials: BA
authors.lastname: Beidleman
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Muza
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fulco
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rock
authors.forename: Allen
authors.initials: A
authors.lastname: Cymerman
mesh_terms: D000064:Acclimatization; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000503:physiopathology* / Q000517:prevention & control*; D002245:Carbon Dioxide; D045853:Exhalation; D006339:Heart Rate; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010953:Plasma Volume; D012111:Residence Characteristics; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen