[Exercise and the detection of severe acute mountain sickness]

Acute mountain sickness (AMS) is a group of non-specific symptoms, seen in subjects that ascend from low to high altitude too quickly, without allowing sufficient time to acclimatize. Usually it is self-limiting, but the severe forms (pulmonary and cerebral edema) can be fatal. Exaggerated hypoxemia at rest is related to later development of AMS but its predictive value is limited. Since exercise at altitude induces greater hypoxemia and symptoms, we postulated the predictive value of a simple exercise test to prognosticate severe AMS. We studied the predictive value of the oxygen saturation during rest and sub-maximum exercise at 2.700 m and 4.300 m in 63 subjects that intended the ascent to Mount Aconcagua (6.962 m). We considered exercise oxygen desaturation to a drop of 5% respect to the resting value. Lake-Louise Score was used to quantify the presence of severe AMS. Six subjects developed severe AMS (9.5%) and required evacuation. Resting oxygen saturation at 2.700 m was not significant to classify subjects that then developed severe AMS. The association of oxygen desaturation during exercise at 2.700 m plus inappropriate resting oxygen saturation at 4.300 m was significant to classify the subjects that then developed severe AMS with a positive predictive value of 80% and a negative predictive value of 97%. Our results are relevant for mountaineering and suggest the use of a simple exercise test in the prediction of severe AMS.