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.

The Effect of Adding CO2 to Hypoxic Inspired Gas on Cerebral Blood Flow Velocity and Breathing during Incremental Exercise

“…We deem it unlikely that differences in experimental setup are sufficient to account for these discrepant findings between the three studies. An alternative explanation is the potential influence of (partial) altitude acclimatization [30] . Subudhi et al, [15] examined the effect of CO 2 clamping on competitive cyclists living and training at 1,650 m, therefore already acclimatized to exercise at moderate altitude.…”

Predicted Hematologic and Plasma Volume Responses Following Rapid Ascent to Progressive Altitudes

“…A recent meta-analysis also found that the extent of the erythropoietic response to altitude is dependent on the initial red cell volume [8] with attenuated increases in individuals with high initial red cell volumes. In a similarmanner, other studies reported that moderate-altitude residents starting with a 6%-13%higher [Hb] than sea-level residents demonstrate an attenuated increase in [Hb] as a result of exposure to a higher altitude[27,45]. The rough correction factors only consider one initial starting level of [Hb] and Hct for both men and women.…”

Vorbereitung für Trekking und Höhenbergsteigen

“…Bedeutsame Akklimatisationseffekte und wesentlich bessere Verträglichkeit eines Höhenanstiegs werden durch Voraufenthalte in Höhenlagen um etwa 2000 m berichtet [6], aber auch Aufenthalte in simulierter Höhe (Höhenräume in Tallage) können unter bestimmten Voraussetzungen zu Akklimatisationszwecken genutzt werden.…”

“…Neben den erwähnten Akklimatisationsempfehlungen vor Ort, kann auch die "Vorakklimatisation" vor der Durchführung von bergsportlichen Aktivitäten in größeren Höhen eine besondere Rolle spielen [4,6]. Literatur…”