title: Validation of multifrequency bioelectrical impedance analysis in monitoring fluid balance in healthy elderly subjects.
abstract: BACKGROUND
  Multifrequency Bioelectrical Impedance Analysis (MFBIA) is a novel method to assess body composition in elderly subjects. However, it is unclear whether MFBIA can detect changes in body water compartments in elders. We aimed to determine the within-subject variability of MFBIA and the responsiveness to a diuretic intervention in aged subjects with a stable fluid balance.
  
  
  METHODS
  We selected 12 healthy active elderly subjects (5 male, 7 female) with a mean age of 75 years. Total body water and extracellular fluid (ECF) were measured by deuterium oxide- and potassium bromide-dilution techniques. Within-subject variability in total body MFBIA was assessed by performing four measurements at 1, 5, 50, and 100 kHz within a 2-month period. Subsequently, responsiveness of MFBIA to the ECF loss caused by oral administration of 40 mg of furosemide was determined.
  
  
  RESULTS
  Within-subject variability in MFBIA at 1, 5, 50, and 100 kHz expressed as standard deviations was 21, 19, 14, and 14 Ohm (omega), respectively. Furosemide caused a mean weight loss of 1.8 +/- 0.6 kg, which resulted in significant increases in impedance of 57 +/- 24 omega at 1 kHz and 37 +/- 12 omega at 100 kHz (p < .001). The responsiveness of MFBIA for the diuretic intervention was best at 5 kHz (responsiveness index = 1.98).
  
  
  CONCLUSIONS
  Within-subject variability of MFBIA was small in healthy elderly subjects with stable fluid balance. Responsiveness of MFBIA to 9% furosemide-induced ECF loss was excellent. These data support the necessity for further clinical assessment of the value of MFBIA in monitoring fluid balance in geriatric patients.
authors.affiliation: Department of Geriatric Medicine, University of Nijmegen, The Netherlands.
authors.forename: M G
authors.initials: MG
authors.lastname: Olde Rikkert
authors.forename: P
authors.initials: P
authors.lastname: Deurenberg
authors.forename: R W
authors.initials: RW
authors.lastname: Jansen
authors.forename: M A
authors.initials: MA
authors.lastname: van't Hof
authors.forename: W H
authors.initials: WH
authors.lastname: Hoefnagels
mesh_terms: D000368:Aged; D000375:Aging / Q000378:metabolism*; D001826:Body Fluids / Q000378:metabolism*; D001834:Body Water / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D004232:Diuretics / Q000494:pharmacology; D017097:Electric Impedance; D005069:Evaluation Studies as Topic; D005260:Female; D005544:Forecasting; D005665:Furosemide / Q000494:pharmacology; D006801:Humans; D008297:Male; D008954:Models, Biological; D012016:Reference Values
chemical_list: D004232:Diuretics; D005665:Furosemide