title: Comparison of thoracic bioimpedance with acetylene uptake for measuring cardiac output.
abstract: Cardiac output is shown to be a key determinant for oxygen transport, performance and health. Reliable and accurate non-invasive measurements of cardiac output, especially during exercise, are therefore of importance. The present study compared a new thoracic bioimpedance method with the established single-breath acetylene uptake method. We assessed cardiac output in 20 (24±4 years.) moderately trained males, at rest and during cycling. Both methods showed good test-retest reliabilities with ±2 SD limits of agreement of 3.67 and -4.50 L ∙ min(-1) (thoracic bioimpedance) and 4.46 and -5.69 L ∙ min(-1) (single breath), respectively. When thoracic bioimpedance was compared with single breath, the ±2 SD limits of agreement were poor (-6.05 and 9.57 L ∙ min(-1)). Thoracic bioimpedance displayed significantly lower (p<0.05) absolute cardiac output values than single breath, and the cardiac output-oxygen consumption slopes (y=5.7x+5.5 (single breath) and y=5.0x+5.0 (thoracic bioimpedance) tended (p=0.08) to show less increase for thoracic bioimpedance.
  
  
  CONCLUSIONS
  Results from the single-breath method are in line with previous findings, showing a good reliability. Although thoracic bioimpedance showed a similar reliability as the single-breath method, and is easier to use, the agreement with single breath was poor, and thoracic bioimpedance seems not to be able to replace it.
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, the Norwegian University of Science and -Technology, Trondheim, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Wang
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, the Norwegian University of Science and -Technology, Trondheim, Norway.
authors.forename: C
authors.initials: C
authors.lastname: Cruz
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, the Norwegian University of Science and -Technology, Trondheim, Norway.
authors.forename: M R
authors.initials: MR
authors.lastname: Pettersen
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, the Norwegian University of Science and -Technology, Trondheim, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Hoff
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, the Norwegian University of Science and -Technology, Trondheim, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Helgerud
mesh_terms: D000114:Acetylene / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000280:Administration, Inhalation; D000328:Adult; D002302:Cardiac Output / Q000502:physiology*; D002307:Cardiography, Impedance; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D013318:Stroke Volume; D055815:Young Adult
chemical_list: D000114:Acetylene