Acute mountain sickness: predictors of climbers’ performance at high altitudes

Objective: To determine the relationship between climber variables (lactic acid levels,

blood pressure, heart rate, respiratory frequency, and peripheral oxygen saturation

[SaO2] and their physical performance and development of acute mountain sickness

(AMS) on the Llullaillaco volcano (6739 m) in Argentina.

Material and methods: As 8 climbers ascended the mountain, we measured lactic acid

and other clinical variables, including SaO2. We also assessed visual acuity (Pelli-Robson

chart), AMS (Lake Louise scoring). SaO2 and heart rate were assessed at rest and on a 6-

minute walk test.

Results: Lactic acid levels of 2 mmol/L or more at 5000 m predicted worsening of a

climber’s condition at higher altitudes, progression to AMS, and declining performance

(positive predictive value, 66.7%; negative predictive value, 100%; precision, 87.5%).

Values on performance of the 6-minute walk test at 5000 m showed that a change of 20

beats/min in heart rate and a 10% change in SaO2 predicted worsening condition at

higher altitudes (specificity, 100%). Likewise, a Lake Louise score of 4 or more at 5000 m

also predicted worsening climber condition and AMS.

Conclusions: Clinical variables and laboratory findings for mountain climbers in base

camps can predict their performance at higher altitudes. A lactic acid level of 2 mmol/L

or more, a change in SaO2 of more than 10% after the walk test and a Lake Louise score

of 4 or more predicted worsening of clinical signs.