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TECHNOLOGY, COMPUTING, AND SIMULATION

Noninvasive Assessment of Cardiac Index in Healthy Volunteers: A Comparison Between Thoracic Impedance Cardiography and Doppler Echocardiography

Jean-Luc Fellahi, MD, PhD^*, Vincent Caille, MD, Cyril Charron, MD, Pierre-Hervé Deschamps-Berger, MD, and Antoine Vieillard-Baron, MD, PhD

From the *Department of Anesthesiology, Centre Hospitalier Privé Saint-Martin, Caen, France; The Intensive Care Unit, Centre Hospitalier Universitaire Ambroise Paré, Assistance Publique-Hôpitaux de Paris, Boulogne, France; and The Department of Cardiology, Polyclinique, Deauville, France.

Address correspondence and reprint requests to Dr. Jean-Luc Fellahi, Service d’Anesthésie réanimation, Centre Hospitalier Privé Saint-Martin, 18 rue des Roquemonts, 14050 Caen Cedex 4, France. Address e-mail to jean-luc.fellahi{at}gdsnb.gsante.fr.

BACKGROUND: Thoracic bioimpedance cardiography (ICG) has been proposed as a noninvasive, continuous, operator-independent, and cost-effective method for cardiac output monitoring. In the present study, we compared cardiac index (CI) measurements with ICG (Niccomo^TM device) and transthoracic Doppler echocardiography in resting healthy volunteers undergoing hemodynamic load challenge.

METHODS: Twenty-five healthy volunteers (7 men and 18 women, mean age 36 ± 6 yr, body surface area 1.75 ± 0.17 m²) were investigated during three experimental conditions: baseline, positive end-expiratory pressure + 10 cm H₂O and lower body positive pressure by means of medical antishock trousers inflated to 30 cm H₂O in the abdominal compartment.

RESULTS: ICG signal quality was >89% over all sets of measurements. A weak but significant relationship was observed between CI_TTE and CI_ICG (r = 0.36; P = 0.002). Agreement between both techniques was 0.94 L · min^–1 · m^–2 (95% CI: 0.77–1.11), limits of agreement were –0.47 to 2.35 L · min^–1 · m^–2, and percentage error was 53%. No statistically significant relationships were found between percent changes in CI_TTE and CI_ICG after applications of positive end-expiratory pressure + 10 cm H₂O (r = 0.21; P = 0.31) and medical antishock trousers (r = 0.22; P = 0.30).

CONCLUSIONS: Poor correlation and lack of agreement between absolute values of CI measured by ICG and transthoracic Doppler echocardiography were found in resting healthy volunteers. The Niccomo device was also unreliable for monitoring changes in CI during hemodynamic load challenge.