Cascade and parallel combination (CPC) of adaptive filters for estimating heart rate during intensive physical exercise from photoplethysmographic signal

• Published in: Healthcare technology letters Vol. 5; no. 1; pp. 18 - 24
• Main Authors: Islam, Mohammad Tariqul, Tanvir Ahmed, Sk, Zabir, Ishmam, Shahnaz, Celia, Fattah, Shaikh Anowarul
• Format: Journal Article
• Language: English
• Published: England The Institution of Engineering and Technology 01.02.2018; John Wiley & Sons, Inc; Wiley
• Subjects: acceleration measurement; Accelerometers; adaptive filters; adaptive noise cancelers; algorithmic approach; cardiology; Electrocardiography; Fitness equipment; Fourier transforms; Heart rate; heart rate monitoring; intensive physical exercise; medical signal processing; motion artefacts; Noise; noise reduction; parallel combination; photoplethysmographic signal; photoplethysmography; Sensors; three-channel accelerometer signals; wearable devices; parallel combination; wearable devices; adaptive filters; acceleration measurement; heart rate monitoring; adaptive noise cancelers; cardiology; medical signal processing; photoplethysmography; three-channel accelerometer signals; intensive physical exercise; noise reduction; photoplethysmographic signal; algorithmic approach; motion artefacts
• ISSN: 2053-3713; 2053-3713
• DOI: 10.1049/htl.2017.0027

Photoplethysmographic (PPG) signal is getting popularity for monitoring heart rate in wearable devices because of simplicity of construction and low cost of the sensor. The task becomes very difficult due to the presence of various motion artefacts. In this study, an algorithm based on cascade and parallel combination (CPC) of adaptive filters is proposed in order to reduce the effect of motion artefacts. First, preliminary noise reduction is performed by averaging two channel PPG signals. Next in order to reduce the effect of motion artefacts, a cascaded filter structure consisting of three cascaded adaptive filter blocks is developed where three-channel accelerometer signals are used as references to motion artefacts. To further reduce the affect of noise, a scheme based on convex combination of two such cascaded adaptive noise cancelers is introduced, where two widely used adaptive filters namely recursive least squares and least mean squares filters are employed. Heart rates are estimated from the noise reduced PPG signal in spectral domain. Finally, an efficient heart rate tracking algorithm is designed based on the nature of the heart rate variability. The performance of the proposed CPC method is tested on a widely used public database. It is found that the proposed method offers very low estimation error and a smooth heart rate tracking with simple algorithmic approach.