Efficient and Direct Inference of Heart Rate Variability using Both Signal Processing and Machine Learning
This work addresses the need for low-error, efficient HRV monitoring on small embedded devices for healthcare applications, though it is incremental in combining existing techniques.
The paper tackled the problem of accurately inferring Heart Rate Variability (HRV) from photoplethysmography (PPG) signals by combining signal processing and machine learning, achieving errors between 3.5% to 25.7% and outperforming prior methods.
Heart Rate Variability (HRV) measures the variation of the time between consecutive heartbeats and is a major indicator of physical and mental health. Recent research has demonstrated that photoplethysmography (PPG) sensors can be used to infer HRV. However, many prior studies had high errors because they only employed signal processing or machine learning (ML), or because they indirectly inferred HRV, or because there lacks large training datasets. Many prior studies may also require large ML models. The low accuracy and large model sizes limit their applications to small embedded devices and potential future use in healthcare. To address the above issues, we first collected a large dataset of PPG signals and HRV ground truth. With this dataset, we developed HRV models that combine signal processing and ML to directly infer HRV. Evaluation results show that our method had errors between 3.5% to 25.7% and outperformed signal-processing-only and ML-only methods. We also explored different ML models, which showed that Decision Trees and Multi-level Perceptrons have 13.0% and 9.1% errors on average with models at most hundreds of KB and inference time less than 1ms. Hence, they are more suitable for small embedded devices and potentially enable the future use of PPG-based HRV monitoring in healthcare.