title: Bioreactance is a reliable method for estimating cardiac output at rest and during exercise.
abstract: BACKGROUND
  Bioreactance is a novel noninvasive method for cardiac output measurement that involves analysis of blood flow-dependent changes in phase shifts of electrical currents applied across the thorax. The present study evaluated the test-retest reliability of bioreactance for assessing haemodynamic variables at rest and during exercise.
  
  
  METHODS
  22 healthy subjects (26 (4) yrs) performed an incremental cycle ergometer exercise protocol relative to their individual power output at maximal O2 consumption (Wmax) on two separate occasions (trials 1 and 2). Participants cycled for five 3 min stages at 20, 40, 60, 80 and 90% Wmax. Haemodynamic and cardiorespiratory variables were assessed at rest and continuously during the exercise protocol.
  
  
  RESULTS
  Cardiac output was not significantly different between trials at rest (P=0.948), or between trials at any stage of the exercise protocol (all P>0.30). There was a strong relationship between cardiac output estimates between the trials (ICC=0.95, P<0.001) and oxygen consumption (ICC=0.99, P<0.001). Stroke volume was also not significantly different between trials at rest (P=0.989) or during exercise (all P>0.15), and strong relationships between trials were found (ICC=0.83, P<0.001).
  
  
  CONCLUSIONS
  The bioreactance method demonstrates good test-retest reliability for estimating cardiac output at rest and during different stages of graded exercise testing including maximal exertion.
authors: Institute of Neurosciences and Newcastle University Institute for Ageing, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors: T W
authors: TW
authors: Jones
authors: Institute of Cellular Medicine, MoveLab, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors: D
authors: D
authors: Houghton
authors: Institute of Cellular Medicine, MoveLab, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors: S
authors: S
authors: Cassidy
authors: Department of Cardiology, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
authors: G A
authors: GA
authors: MacGowan
authors: Institute of Cellular Medicine, MoveLab, Newcastle University, Newcastle upon Tyne NE2 4HH, UK RCUK Centre for Ageing and Vitality, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors: M I
authors: MI
authors: Trenell
authors: Institute of Cellular Medicine, MoveLab, Newcastle University, Newcastle upon Tyne NE2 4HH, UK RCUK Centre for Ageing and Vitality, Newcastle University, Newcastle upon Tyne NE2 4HH, UK djordje.jakovljevic@newcastle.ac.uk.
authors: D G
authors: DG
authors: Jakovljevic
mesh_terms: D000328:Adult; D002302:Cardiac Output / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology*
keywords: cardiac output; exercise test; haemodynamics; monitoring, physiological