High altitude syndromes at intermediate altitudes: a pilot study in the Australian Alps

Our hypothesis is that symptoms of high altitude syndromes are detectable even at intermediate altitudes, as commonly encountered under Australian conditions (<2500 m above sea level). High altitude medicine has long recognised several syndromes associated with rapid ascent to altitudes above 2500 m, including high altitude pulmonary oedema (HAPE), high altitude cerebral oedema (HACE) and high altitude flatus expulsion (HAFE). Symptoms of high altitude syndromes are of growing concern because of the global trend toward increasing numbers of tourists and workers exposed to both rapid ascent and sustained physical activity at high altitude. However, in Australia, high altitude medicine has almost no profile because of our relatively low altitudes by international standards. Three factors lead us to believe that altitude sickness in Australia deserves more serious consideration: Australia is subject to rapid growth in alpine recreational industries; altitude sickness is highly variable between individuals, and some people do experience symptoms already at 1500 m; and there is potential for an occupational health and safety issue amongst workers. To test this hypothesis we examined the relationship between any high altitude symptoms and a rapid ascent to an intermediate altitude (1800 m) by undertaking an intervention study in a cohort of eight medical clinic staff, conducted during July of the 2012 (Southern Hemisphere) ski season, using self-reporting questionnaires, at Mansfield (316 m above sea level) and at the Ski Resort of Mt Buller (1800 m), Victoria, Australia. The intervention consisted of ascent by car from Mansfield to Mt Buller (approx. 40 min drive). Participants completed a self-reporting questionnaire including demographic data and information on frequency of normal homeostatic processes (fluid intake and output, food intake and output, symptoms including thirst and headaches, and frequency of passing wind or urine). Data were recorded in hourly periods extending over 18 h before and 18 h after ascent. We found that the frequency of flatus production more than doubled following ascent, with a post-ascent frequency of approximately 14 expulsions per person over the 18 h recording period (Rate Ratio 2.31, CI 1.33-3.99, p=0.003). The frequency and severity of headaches also increased following ascent. These results support the hypothesis that high altitude symptoms can be significant issues even at the relatively lower altitudes encountered in Australian alpine regions. Increased awareness amongst clinicians of this possibility could contribute to a reduction in the disease burden from high altitude syndromes at intermediate altitudes.