Two Days of Staging at Moderate Altitude Reduces Acute Mountain Sickness Upon Further Ascent to 4300 m in Unacclimatized Lowlanders

Abstract

Four or more days of staging at moderate altitude reduces acute mountain sickness (AMS) in unacclimatized lowlanders during subsequent ascent to high altitude. The impact of two days of staging at moderate altitude on reducing AMS is unknown. Two independent groups of unacclimatized men were staged at either 2500 m (n=12, 23±3 yr, 80±6 kg, mean±SD) or 3000 m (n=7, 23±2 yr, 79±6 kg) for 2 days prior to ascent to 4300 m and were compared to a control group that directly ascended to 4300 m (n=7, 21±3 yr, 76±4 kg). Following 22 h of exposure to 4300 m, AMS was measured using the Environmental Symptoms Questionnaire and AMS‐C score and arterial oxygen saturation (SaO2) was measured using pulse oximetry. AMS prevalence and severity at 4300 m were lower (P<0.05) in the 2500 m group (42% and 0.59±0.38) and 3000 m group (29% and 0.51±0.39) compared to the control group (73% and 1.21±0.48). AMS prevalence and severity at 4300 m was not different (P>;0.05) between the two staged groups. SaO2 was higher (P<0.05) in the 2500 m group (82±4%) and 3000 m group (84±4%) at 4300 m compared to the control group (79±3%) but was not different (P>;0.05) between the two staged groups. These results demonstrate that two days of staging at either 2500 m or 3000 m is effective for reducing AMS and increasing SaO2 during subsequent exposure to 4300 m. Funding: USAMRMC. Authors’ views; not official U.S. Army or DoD policy.