Impedance cardiac profile monitoring by a modified ensemble averaging technique

A real-time algorithm is developed to modify the ensemble averaging so that it averages nonperiodic signals, such as ECG (electrocardiogram), dz/dt, Delta z, etc., for impedance cardiac profile monitoring. A real-time algorithm is developed top detect R spikes adaptively from ECG signals. A signal preprocessor is developed to process signals digitally before any further work is done. This method reduces muscle noise, 60-Hz interference, and respiration effect. 144 sets of data from five healthy volunteers, four critically ill patients and three healthy exercising volunteers have been tested. Correlation studies between the authors´ system and standard hand calculation of stroke volume, based on Kubiceks equations, show relatively high and stable correlation coefficients; r=0.93, p<0.005 (healthy); r=0.94, p<0.002 (ill); r=0.95, p<0.002 (exercise). Apnea is not necessary during any of the studies.<>