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

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 m(2)) 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 CITTE and CIICG (r = 0.36; P = 0.002). Agreement between both techniques was 0.94 L . min(-1) . m(-2) (95% CI: 0.77-1.1.1), 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 CITTE and CIICG 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 Cl measured by ICG and transthoracic Doppler echocardiography were found in resting healthy Volunteers. The Niccomo device was also unreliable for monitoring changes in Cl during hemodynamic load challenge.