Impedance cardiography for monitoring changes in cardiac output.

Impedance Cardiography (ICG) is a non invasive method useful for continuous monitoring of cardiac output but, it still has not found wide usage for measuring cardiac output in clinics and research. Most studies focused on comparing the cardiac output measured at rest with reference methods. In the present study we evaluated the validity of ICG against Doppler Echocardiography (DE) in measuring cardiac output changes that occur during static exercise. Cardiac output of 30 healthy males between 18-26 yrs of age was measured during supine rest, during and 5 min after completion of 3 minute static exercise by ICG and DE. The increase in cardiac output during exercise measured with ICG and DE does not differ significantly (1.04 +/- 0.72 L/min and 1.05 +/- 1.24 L/min respectively) and has significantly high correlation (r = 0.76, P < 0.001). The bias and limits of agreement are (-0.01 +/- 0.83) in acceptable limits. The pooled means of cardiac output measured by ICG and DE do not differ significantly and bears a significant correlation (r = 0.812, P < 0.001). The bias (d +/- s) calculated is 0.15 +/- 0.64 L/min. ICG could provide valid information regarding the relative changes in cardiac output.