A Novel Method for Heart Rate Measurement Using Bioimpedance

The aim of the present study was to test the validity of a novel technique for measurement of heart rate on a standing subject. This noninvasive method relies on variations in electrical bioimpedance detected by a plantar interface with both feet such as those in some bathroom weighing scales for body composition analysis. Heart related impedance variations in the legs come from arterial blood circulation and are below 50 milliohms. This system injects a safe AC current into the patient through the soles of both feet and measures basal impedance which is related to body composition analysis. To detect the small variations in impedance, we have implemented a system with fully differential AC input amplifier. The system sensitivity is 610 mV/Ω. The technique was demonstrated on volunteers whose bioimpedance signal and ECG were simultaneously recorded. This method is simple and user friendly and does not require any conductive gel or skin preparation.