title: Comparison of two methods of assessing total body water at sea level and increasing high altitude.
abstract: 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<0.0001) and at HA (r = 0.92; 0.89-0.94: P<0.0001), however, TBW readings were 0.2 l and 1.91 l lower, respectively, with the NICaS. There was a stronger correlation between TBW and body weight with the QuadScan (r = 0.91; P<0.0001) than with the NICaS (r = 0.83; P<0.0001). The overall agreement between the two TBW methods was good, but the 95% confidence intervals around these agreements were relatively wide. We conclude that there was reasonable agreement between the two methods of BIA for TBW, but this agreement was lower at HA.
authors.affiliation: Defence Medical Services, Department of Postgraduate Medicine, Lichfield, UK; Department of Cardiology, Poole Hospital NHS Foundation Trust, Dorset, UK; Centre of Postgraduate Medical Research & Education, Bournemouth University, Bournemouth, UK; Department of Cardiology, Royal Berkshire Hospital, Reading, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Boos
authors.forename: D A
authors.initials: DA
authors.lastname: Holdsworth
authors.forename: D P
authors.initials: DP
authors.lastname: Hall
authors.forename: A
authors.initials: A
authors.lastname: Mellor
authors.forename: J
authors.initials: J
authors.lastname: O'Hara
authors.forename: D R
authors.initials: DR
authors.lastname: Woods
mesh_terms: D000328:Adult; D000531:Altitude; D001823:Body Composition; D001834:Body Water / Q000378:metabolism*; D017097:Electric Impedance; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
keywords: BodyStat NICaS; bioimpedance analysis; exercise; high altitude; total body water