title: Impedance cardiography: the next vital sign technology?
abstract: OBJECTIVE
  To evaluate the following: (1) the intramethod variability of impedance cardiography (ICG) cardiac output (CO) measurements via the latest generation monitor and thermodilution CO measurements (CO-TDs); (2) the intermethod comparison of ICG CO and CO-TD; and (3) comparisons of the intergeneration ICG CO equation to CO-TD, using the latest ICG CO equation, the ZMARC (CO-ICG), and the predecessor equations for measuring the ICG CO of Kubicek (CO-K), Sramek (CO-S), and Sramek-Bernstein (CO-SB).
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  A cardiovascular-thoracic surgery ICU in a community university-affiliated hospital.
  
  
  METHODS
  Post-coronary artery bypass graft patients (n = 53) in whom 210 pairs of CO measurements were made.
  
  
  METHODS
  None.
  
  
  RESULTS
  The CO-ICG was determined simultaneously while the nurse was performing the CO-TD. Variability within the monitoring method was better for CO-ICG compared to CO-TD (6.3% vs 24.7%, respectively). The correlation, bias, and precision of the CO-ICG was good compared to CO-TD (r(2) = 0.658; r = 0.811; bias, -0.17 L/min; precision, 1.09 L/min; CO-ICG = 1.00 x CO-TD - 0.17; p < 0.001). A steady improvement in agreement of the previous ICG methodologies compared to CO-TD was observed as follows: (1) CO-K: r(2) = 0.309; r = 0.556; bias, -1.71 L/min; precision, 1.81 L/min; CO-K = 0.78 x CO-TD - 0.45; p < 0.001; (2) CO-S: r(2) = 0.361; r = 0.601; bias, -1.46 L/min; precision, 1.63 L/min; CO-S = 0.80 x CO-TD - 0.36; p < 0.001; and (3) CO-SB: r(2) = 0.469; r = 0.685; bias, -0.77 L/min; precision, 1.69 L/min; CO-SB = 1.03 x CO-TD - 0.95; p < 0.001. The CO-ICG demonstrated the closest agreement to CO-TD.
  
  
  CONCLUSIONS
  The latest ICG technology for determining CO (CO-ICG) is less variable and more reproducible in an intrapatient sense than is CO-TD, it is equivalent to the average accepted CO-TD in post-coronary artery bypass graft patients, and showed marked improvement in agreement with CO-TD compared to measurements made using previous generation ICG CO equations.
authors.affiliation: Department of Surgery, Mercer University School of Medicine, Macon, GA 31201, USA. Vandewater.joseph@mccg.org
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Van De Water
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Miller
authors.forename: Robert L
authors.initials: RL
authors.lastname: Vogel
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Mount
authors.forename: Martin L
authors.initials: ML
authors.lastname: Dalton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002302:Cardiac Output / Q000502:physiology*; D002307:Cardiography, Impedance; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013815:Thermodilution