Efficacy of Residence at Moderate Versus Low Altitude on Reducing Acute Mountain Sickness in Men Following Rapid Ascent to 4300 m

Abstract

Abstract

Staab, Janet E., Beth A. Beidleman, Stephen R. Muza, Charles S. Fulco, Paul B. Rock, and Allen Cymerman. Efficacy of residence at moderate versus low altitude on reducing acute mountain sickness in men following rapid ascent to 4300 m. High Alt Med Biol 14:13–18, 2013.—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 (P_ETco₂) 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.