Dynamic Metrics of Heart Rate Variability

Numerous metrics of heart rate variability (HRV) have been described, analyzed, and compared in the literature. However, they rarely cover the actual metrics used in a class of HRV data acquisition devices - those designed primarily to produce real-time metrics. This paper characterizes a class of metrics that we term dynamic metrics. We also report the results of a pilot study which compares one such dynamic metric, based on photoplethysmographic data using a moving sampling window set to the length of an estimated breath cycle (EBC), with established HRV metrics. The results show high correlation coefficients between the dynamic EBC metrics and the established static SDNN metric (standard deviation of Normal-to-Normal) based on electrocardiography. These results demonstrate the usefulness of data acquisition devices designed for real-time metrics.