Reducing the influence of contacting force applied on photoplethysmographic sensor on heart rate variability estimation

The performance of a heart rate (HR) and heart rate variability (HRV) monitor based on photoplethysmography (PPG) can be significantly degraded by the variations in contacting force applied on the sensor. This paper presents a wavelet approach to evaluate and reduce the influence of the force variations on the estimation of HR and HRV. The experiment was conducted on eighteen healthy subjects under three different force conditions - low, medium and high, respectively. The preliminary results indicate that reasonably accurate parameter estimation can be achieved from considerably distorted PPG signals even at a single scale of continuous wavelet transform (CWT).