title: A comparative evaluation of electrical velocimetry and inert gas rebreathing for the non-invasive assessment of cardiac output.
abstract: BACKGROUND
  When assessing the function of the cardiovascular system, cardiac output (CO) is a substantial parameter. For its determination, numerous non-invasive techniques have been proposed in the recent years including inert gas rebreathing (IGR) and impedance cardiography (ICG). The aim of our study was to evaluate whether a novel ICG algorithm (electrical velocimetry) and IGR can be used interchangeably in the clinical setting.
  
  
  METHODS
  A total of 120 consecutive stable patients were included resulting in two pairs of repeated non-invasive cardiac output measurements.
  
  
  RESULTS
  The mean CO was 5.0 ± 1.2 l/min (range 2.6-8.6 l/min) using IGR and 4.4 ± 1.1 l/min (1.7-7.4 l/min) using ICG, respectively. Bland-Altman analysis revealed an acceptable agreement with a mean bias of 0.6 ± 1.2 l/min. We found a high reproducibility with a mean bias of 0.2 ± 0.7 l/min for IGR and 0.0 ± 0.3 l/min for ICG (p < 0.001), respectively. There was a statistically significant difference for unphysiological circulatory conditions represented by values of 2.6-4.1 l/min and 5.6-8.6 l/min.
  
  
  CONCLUSIONS
  Both non-invasive techniques are associated with low operating costs and require only a few expendable items for the rapid determination of cardiac function. We found an acceptable agreement between IGR and ICG as well as a high reproducibility, which was statistically significant higher for ICG. For cardiac output states exceeding the physiological range, we found a statistically significant difference. Consequently, values of cardiac function determined by either method should not be used interchangeably in the clinical setting.
authors: First Department of Medicine (Cardiology, Angiology, Pneumology, Intensive Care), Universitätsmedizin Mannheim, University of Heidelberg, Germany.
authors: Frederik
authors: F
authors: Trinkmann
authors: Manuel
authors: M
authors: Berger
authors: Ursula
authors: U
authors: Hoffmann
authors: Martin
authors: M
authors: Borggrefe
authors: Jens J
authors: JJ
authors: Kaden
authors: Joachim
authors: J
authors: Saur
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001944:Breath Tests; D002302:Cardiac Output; D002307:Cardiography, Impedance; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D005858:Germany; D006334:Heart Function Tests / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013459:Sulfur Hexafluoride; D013997:Time Factors; D055815:Young Adult
chemical_list: D009609:Nitrous Oxide; D013459:Sulfur Hexafluoride