Multiple frequency bioelectrical impedance analysis to assess body fluid composition changes with altitude

Abstract

In this study, the body fluid composition changes due to exposure to high altitude isassessed by multifrequency and multisite bioimpedance analysis. For this purpose a portableBioimpedance Analyzer that is capable of measuring the resistance and the reactance of thetissues and body parts at five different frequencies is designed. To assess the effects ofaltitude, the instrument is used in performing multifrequency bioimpedance analysis on 10subjects who participated in the third week of Kac;kar 94 Expedition. Kac;kar 94 ExpeditionofBogaziC;i University Skin and Scuba Club (BUS AS) lasted for three weeks on Mt. Kac;kar(3412m.). The data are collected before, during and after the expedition and discussed toinvestigate the effects of altitude on body fluid composition changes.Based on the empirical formulas of previous studies, the Fat Free Mass is observedto decrease with high altitude due to the dehydration during the trip, the heavy activitiescausing depletion of fat reserves and by the effect of hypoxia which is a part of the acutemountain sickness.To question the overestimation in previous studies that use 50kHz bioimpedanceanalysis to assess body fluid changes with altitude, a different approach based on Cole-Coleplot that was used to calculate the characteristic frequency fe, Ro and Roo. A large increasein fc value was observed regardless of the site of measurement upon initial exposure tohypoxia, followed by a gradual increase, recovering back to the original value upon comingback. In this way we can deduce that the body composition change during acute exposure tohypoxia and heavy exercise during climbing and trekking.The individual analysis of the trunk is compulsory to assess the body fluidcomposition change. But due to the anthropometric factors, the trunk measurements are notreliable. However a higher percent variation in the resistance of the trunk R compared to thearms at 5kHz measurement is explained by a change in extracellular fluid composition andthe trace of the trunk measurement changes which display a decrease followed by arecovery in the acclimatization and returning back suggests a local edema, probably in thelungs which remained subclinical to the subjects.