Using simple exercise tests in the field to assess susceptibility to Acute Mountain Sickness; the Chester Step Test may be a useful predictor

Introduction We undertook an observational study with eight volunteer participants which aimed to identify whether simple cardio-respiratory measurements, before and after different forms of exercise testing, could offer a reliable means of predicting Acute Mountain Sickness (AMS). Three tests were used, all of which were easily performed in the mountain environment. Methods During an expedition to Mt Elbrus (5642m), in the Caucasus region of Russia, daily cardiorespiratory observations were made on eight subjects after exercise testing, and compared with Lake Louise Self-Assessment Questionnaire (LLSAQ) scores. Results At all altitudes, the Chester Step Test (CST) demonstrated differences in the time taken to reach 80% of the calculated maximum heart rate between participants due to variance in levels of aerobic fitness. At 3800m, there was a significant difference (t = 3.06, p = 0.02) between those who reached 80% of their maximum heart rate rapidly, and those who did not. This difference was associated with symptoms of severe AMS; the group who developed more severe symptoms were able to exercise for longer than the group who demonstrated mild AMS (Mann-Whitney U score: p = 0.004). Conclusions Despite small numbers, these results suggest that there is a difference between mountaineers who develop severe AMS and those who are less severely affected, upon testing of their aerobic capacity. This may reflect adaptation of the cardiovascular system, and further investigation is warranted.