title: Evaluation of body composition in COPD patients using multifrequency bioelectrical impedance analysis.
abstract: BACKGROUND
  Multifrequency bioelectrical impedance analysis (MF-BIA) is a technique that measures body impedance (Z) at different frequencies (5, 10, 50, 100, and 250 kHz). Body composition may be estimated using empirical equations, which include BIA variables or, alternatively, raw BIA data may provide direct information on water distribution and muscle quality.
  
  
  OBJECTIVE
  To compare raw MF-BIA data between COPD patients and controls and to study their relationship with respiratory and functional parameters in COPD patients.
  
  
  METHODS
  MF-BIA was performed (Human Im-Touch analyzer) in 212 COPD patients and 115 age- and BMI-matched controls. Fat-free mass (FFM) and fat mass were estimated from BIA data, and low- to high-frequency (5 kHz/250 kHz) impedance ratio was calculated. Physical fitness, lung function and respiratory muscle strength were also assessed in COPD patients.
  
  
  RESULTS
  After adjusting for age, weight, and body mass index, FFM and the 5/250 impedance ratio were lower in COPD patients (P<0.001) and were negatively affected by disease severity. In both male and female patients, the 5/250 impedance ratio was significantly correlated mainly with age (r=-0.316 andr=-0.346, respectively). Patients with a 5/250 impedance ratio below median value had lower handgrip strength (P<0.001), 6-minute walk distance (P<0.005), respiratory muscle strength (P<0.005), forced expiratory volume in 1 second (P<0.05) and vital capacity (P<0.005). Finally, the 5/250 impedance ratio was reduced (P<0.05) in patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) III and IV (compared to those with GOLD I and II) or a BODE index between 6 and 10 points (compared to those with BODE index between 1 and 5 points).
  
  
  CONCLUSIONS
  MF-BIA may be a useful tool for assessing body composition and nutritional status in COPD patients. In particular, the impedance ratio could give valuable information on cellular integrity and muscle quality.
authors.affiliation: Department of Public Health, Medical School, "Federico II" University of Naples.
authors.forename: Francesca
authors.initials: F
authors.lastname: de Blasio
authors.affiliation: Respiratory Medicine and Pulmonary Rehabilitation Section, Clinic Center, Private Hospital, Naples; Department of Medicine and Health Sciences "V Tiberio", University of Molise, Campobasso.
authors.forename: Francesco
authors.initials: F
authors.lastname: de Blasio
authors.affiliation: Respiratory Medicine and Pulmonary Rehabilitation Section, Clinic Center, Private Hospital, Naples.
authors.forename: Giulia
authors.initials: G
authors.lastname: Miracco Berlingieri
authors.affiliation: Department of Medicine and Health Sciences "V Tiberio", University of Molise, Campobasso; Department of Cardio-Thoracic and Respiratory Sciences, Second University of Naples, Naples, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bianco
authors.affiliation: Department of Public Health, Medical School, "Federico II" University of Naples.
authors.forename: Marta
authors.initials: M
authors.lastname: La Greca
authors.affiliation: Department of Research and Education, CIRO, Horn, the Netherlands.
authors.forename: Frits M E
authors.initials: FM
authors.lastname: Franssen
authors.affiliation: Department of Public Health, Medical School, "Federico II" University of Naples.
authors.forename: Luca
authors.initials: L
authors.lastname: Scalfi
mesh_terms: D050154:Adiposity; D000368:Aged; D001823:Body Composition; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D007558:Italy; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D009752:Nutritional Status; D010809:Physical Fitness; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D012132:Respiratory Muscles / Q000503:physiopathology; D014797:Vital Capacity; D000070857:Walk Test
keywords: impedance ratio; muscle quality; muscle strength