Impedance Cardiography^*

The Next Vital Sign Technology?

Van De Water, Joseph M. MD, FCCP
Miller, Timothy W. RRT
Vogel, Robert L. PhD
Mount, Bruce E. BS
Dalton, Martin L. MD

^*From the Departments of Surgery (Drs. Van De Water and Dalton, and Mr. Miller and Mr. Mount) and Family Practice (Dr. Vogel), Mercer University School of Medicine, Macon, GA.

Manuscript received June 11, 2002; revision accepted October 31, 2002.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e-mail: [email protected]).

Correspondence to: Joseph M. Van De Water, MD, FCCP, Department of Surgery, Mercer University School of Medicine, Macon, GA 31201; e-mail:[email protected].

Chest 123(6):p 2028-2033, June 2003.

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).

Design:

Prospective study.

Setting:

A cardiovascular-thoracic surgery ICU in a community university-affiliated hospital.

Patients:

Post-coronary artery bypass graft patients (n = 53) in whom 210 pairs of CO measurements were made.

Interventions:

None.

Measurements and main 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 (r² = 0.658;r= 0.811; bias, -0.17 L/min; precision, 1.09 L/min; CO-ICG = 1.00 × 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:r² = 0.309;r= 0.556; bias, -1.71 L/min; precision, 1.81 L/min; CO-K = 0.78 × CO-TD - 0.45; p < 0.001; (2) CO-S:r² = 0.361;r= 0.601; bias, -1.46 L/min; precision, 1.63 L/min; CO-S = 0.80 × CO-TD - 0.36; p < 0.001; and (3) CO-SB:r² = 0.469;r= 0.685; bias, -0.77 L/min; precision, 1.69 L/min; CO-SB = 1.03 × CO-TD - 0.95; p < 0.001. The CO-ICG demonstrated the closest agreement to CO-TD.

Conclusion:

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.

Impedance Cardiography*