Purpose: Acute mountain sickness (AMS) is a neurological disorder that may be unpredictably experienced by subjects ascending at a high altitude. The aim of the present study was to develop a predictive index, measured at an intermediate altitude, to predict the onset of AMS at a higher altitude.
Methods: In the first part, 47 subjects were investigated and blood withdrawals were performed before ascent, at an intermediate altitude (3440 m), and after acute and chronic exposition to high altitude (Mount Everest Base Camp, 5400 m (MEBC1 and MEBC2)). Parameters independently associated to the Lake Louise scoring (LLS) system, including the self-reported and the clinical sections, and coefficients estimated from the model obtained through stepwise regression analysis were used to create a predictive index. The possibility of the index, measured after an overnight stay at intermediate altitude (Gnifetti hut, 3647 m), to predict AMS (defined as headache and LLS ≥ 4) at final altitude (Capanna Margherita, 4559 m), was then investigated in a prospective study performed on 44 subjects in the Italian Alps.
Results: During the expedition to MEBC, oxygen saturation, hematocrit, day of expedition, and maximum velocity of clot formation were selected as independently associated with LLS and were included in the predictive index. In the Italian Alps, subjects with a predictive index value ≥ 5.92 at an intermediate altitude had an odds ratio of 8.1 (95% confidence limits = 1.7-38.6, sensitivity = 85%, specificity = 59%) for developing AMS within 48 h of reaching high altitude.
Conclusion: In conclusion, a predictive index combining clinical and hematological parameters measured at an intermediate step on the way to the top may provide information on impending AMS.
1Department of Medical and Surgical Critical Care, University of Florence, ITALY; 2Fondazione Don Carlo Gnocchi, Centro di S. Maria degli Ulivi, Florence, ITALY; 3Department of Cardiology, Ospedale S. Luca, Istituto Auxologico Italiano, Milan, ITALY; 4Department of Clinical Medicine and Prevention, University of Milan-Bicocca, Milan, ITALY; 5Centro Cardiologico Monzino IRCCS, Department of Cardiology, University of Milan, ITALY; and 6Department of Statistics G. Parenti, University of Florence, Florence, ITALY
Address for correspondence: Pietro Amedeo Modesti, M.D., Ph.D., Clinica Medica Generale e Cardiologia, University of Florence, Viale Morgagni 85, 50134 Florence, Italy; E-mail: firstname.lastname@example.org.
Submitted for publication December 2010.
Accepted for publication March 2011.