Comparison of two methods of assessing total body water at sea level and increasing high altitude

Summary Fluid retention is a recognized feature of acute mountain sickness. However, accurate assessment of hydration, including the quantification of body water, has traditionally relied on expensive and non‐portable equipment limiting its utility in the field setting. We compared the assessment of total body water (TBW) and their relationship to total body weight using two non‐invasive methods using the NICas single‐frequency bioimpedance analysis (SF‐BIA) system and the BodyStat QuadScan 4000 multifrequency BIA system (MF‐BIA). TBW measurements were performed at rest at sea level and at high altitude (HA) at 3833 m postexercise and at rest and thereafter at rest at 4450 m and 5129 m on 47 subjects. The average age was 34·5 ± 9·3 years with an age range of 21–54 years (70·2% male). There were strong correlations between TBW assessment with both methods at sea level (r = 0·90; 95% CI 0·78–0·95: P