Computer-assisted method for performing impedance cardiography calculations.

Abstract

Impedance cardiography provides a noninvasive technique to monitor stroke volume on a beat-by-beat basis. It correlates well with other techniques at rest, with both cycle and arm-ergometer exercise, and during head-up tilt. It has the advantage that it does not require active subject participation, as does the CO2-rebreathing technique; yet it is still noninvasive. The method described herein facilitates the measurement and calculation of stroke volume, cardiac output, and indices of ventricular function when this technique is used - whether a few or many beats are recorded. This method utilizes a recording of the impedance cardiogram, which may include a simultaneously recorded electrocardiogram and phonocardiogram; a digitizer for reading the coordinates from the recording; a CRT terminal with keyboard for additional data input and for monitoring output; a printer; and a minicomputer for calculation of variables and data analysis. Data related to approximately 100 cardiac beats can be read, calculated, printed, and statistically analyzed in about an hour.