Effect of Six Days of Staging on Physiologic Adjustments and Acute Mountain Sickness During Ascent to 4300 Meters

This study determined the effectiveness of 6 days (d) of staging at 2200m on physiologic adjustments and acute mountain sickness (AMS) during rapid, high-risk ascent to 4300m. Eleven sea-level (SL) resident men (means +SD; 21+3 yr; 78+13 kg) completed resting measures of end-tidal CO2 (Petco2), arterial oxygen saturation (Sao2), heart rate (HR), and mean arterial pressure (MAP) at SL and within 1 h of exposure to 4300m in a hypobaric chamber prior to 6 d of staging at 2200m (preSTG) and on the summit of Pikes Peak following 6 d of staging at 2200m (postSTG). Immediately following resting ventilation measures, all performed submaximal exercise (~55% of altitude-specific maximal oxygen uptake) for ~2 h on a bicycle ergometer to induce higher levels of AMS. AMS-C, calculated from the Environmental Symptoms Questionnaire, was measured following 4 h and 8 h of exposure at preSTG and postSTG, and the mean was calculated. Resting Petco2 (mmHg) was unchanged from SL (39.8+2.6) to preSTG (39.3+3.0), but decreased ( p<0.05) from preSTG to postSTG (32.8+2.6). Resting Sao2 (%) decreased ( p<0.05) from SL (97+2) to preSTG (80+4) and increased ( p<0.05) from preSTG to postSTG (83+3). Resting HR (bpm) and MAP (mmHg) did not change in any of the test conditions. The incidence and severity of AMS-C decreased ( p<0.05) from preSTG (9130%; 1.050.56) to postSTG (4553%; 0.590.43), respectively. These results suggest that modest physiologic adjustments induced by staging for 6 d at 2200m reduced the incidence and severity of AMS during rapid, high-risk ascent to 4300 m.