An Approach towards Motion-Tolerant PPG-Based Algorithm for Real-Time Heart Rate Monitoring of Moving Pigs

Abstract

Animal welfare remains a very important issue in the livestock sector, but monitoring animal welfare in an objective and continuous way remains a serious challenge. Monitoring animal welfare, based upon physiological measurements instead of the audio–visual scoring of behaviour, would be a step forward. One of the obvious physiological signals related to welfare and stress is heart rate. The objective of this research was to measure heart rate (beat per minutes) in pigs with technology that soon will be affordable. Affordable heart rate monitoring is done today at large scale on humans using the Photo Plethysmography (PPG) technology. We used PPG sensors on a pig′s body to test whether it allows the retrieval of a reliable heart rate signal. A continuous wavelet transform (CWT)-based algorithm is developed to decouple the cardiac pulse waves from the pig. Three different wavelets, namely second, fourth and sixth order Derivative of Gaussian (DOG), are tested. We show the results of the developed PPG-based algorithm, against electrocardiograms (ECG) as a reference measure for heart rate, and this for an anaesthetised versus a non-anaesthetised animal. We tested three different anatomical body positions (ear, leg and tail) and give results for each body position of the sensor. In summary, it can be concluded that the agreement between the PPG-based heart rate technique and the reference sensor is between 91% and 95%. In this paper, we showed the potential of using the PPG-based technology to assess the pig′s heart rate.

Brief research report: Evaluation of photoplethysmographic heart rate monitoring for sheep under heat-stressed conditions

“…Recently conducted PPG tests on pigs (Youssef et al, 2020), cattle (Jun et al, 2013) and dogs (Cugmas et al, 2019) showed promise for PPG use in detecting animal HR in controlled settings; however, more traditional production systems are substantially less controlled. Additionally, limitations related to the applicability of the sensing approach in these systems must be reported for future improvement.…”

“…We expect that the major challenge to address is that of sensor motion, which has been demonstrated to easily affect the quality of PPG signals (Yunjoo et al, 2008). Additionally, other studies evaluating the use of PPG sensors for HR measurements, have tested the technology on anesthetized animals, where the effects of movement and respiration of a conscious animal did not complicate readings (Cugmas et al, 2019;Youssef et al, 2020). Therefore, improved design of sensor attachment and testing of different sensing locations, which allow security to achieve a consistent contact, would be a logical first step in optimizing PPG use for real-time monitoring of livestock HR.…”

“…This reflectance is associated with the variations in blood perfusion of the tissue and has been used to great success in human applications for providing information on HR (Tamura et al, 2014;Nie et al, 2020). However, PPG technology has limited animal applications except for a few, highly controlled studies in pigs (Youssef et al, 2020) and cattle (Jun, Jun et al, 2013). In these studies, animals were anesthetized and shaved to create skin conditions most ideal for PPG sensing.…”

Polynomial, Neural Network, and Spline Wavelet Models for Continuous Wavelet Transform of Signals

“…A significant part of wavelet signal analysis algorithms is based on the use of continuous wavelet transform [1,2,5,6,9]. The analysis of literary sources showed that wavelets are used in the analysis of signals such as electrocardiogram [13][14][15][16], electroencephalogram [6,17,18], seismic signals, signals from various sensors [1], etc.…”

Brief research report: Photoplethysmography pulse sensors designed to detect human heart rates are ineffective at measuring horse heart rates

“…Although the majority of currently available technologies work well for exercise investigation, besides the Polar system, they are not feasible for long-term, continuous heart rate monitoring. Photoplethysmography (PPG) technology has been used to create small, simple, and affordable heart rate sensors that are well-suited to this continuous monitoring application in cattle (Salzer et al, 2022), sheep (Cui et al, 2019), and pigs (Youssef et al, 2020). Since fitness is important in the equine industry, a continuous heart rate monitor may also be useful in exercise settings, much like its use in humans for fitness tracking during workouts as well as day-to-day monitoring.…”