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Four commercial wireless chest belts (Vetta, Nashbar, Polar and new Polar) were assessed for their susceptibility to noises in R-wave detection. A normal ECG signal was generated using a LionHeart simulator (Bio-tek Instruments, Inc.) with a fixed RR interval (750 ms) and R-wave amplitude (1 mV). Different levels of EMG and baseline wanderings (sinusoidal waves) were recorded from a healthy subject and a Quartec Model MFG-1 generator, respectively. They were added to the ECG signal in a BioPac system (BioPac systems Inc., Santa Barbara, CA) to simulate an ECG in physiological noise. The BioPac system applied the 'contaminated' ECG to the belts via a voltage divider. A PC-based Polar Precision Performance system was used to receive the detected R-wave pulses transmitted from the wireless belts and to calculate the RR intervals. Two types of detection errors were observed in the RR intervals: small time shifts, the potentially non-fixable small variance, and missed/false beats, the abnormally large and potentially fixable intervals. Results showed that small time shifts exist in all tests ranging from -10 ms to 10 ms and increase with the level of EMG before missed/false beats occur. Missed/false beats occur only when EMG level is beyond the threshold of 0.4 mV, 1.6 mV, 1.2 mV and 1.2 mV for Vetta, Nashbar, Polar and new Polar, respectively. The potential to detect and fix EMG introduced missed/false beats showed that this type of error could only be improved when the added EMG was below a certain value. Results also showed that no missed/false beats occur when the frequency and amplitude of sinusoidal waves were below 1 Hz and 5 mV.

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