Influence Of Limb Side On Validity Of Heart Rate Variability Data Collected Via Photoplethysmography

A recently validated finger sensor device utilizes photoplethysmography (PPG) and a smartphone application to provide a more feasible method of collecting heart rate variability (HRV) metrics compared to standard techniques. However, the influence of limb side on validity of PPG devices in collecting HRV metrics is unknown, resulting in a lack of standardized procedures. PURPOSE: To determine the influence of limb side in the collection of R-R interval, heart rate (HR), and the natural log of root mean square of the successive differences (lnRMSSD) HRV data via a PPG sensor. METHODS: R-R interval, HR, and lnRMSSD data were simultaneously collected from 20 participants (10 females, 10 males) using PPG sensors on the left and right most distal fingers and an industry standard HR monitor (HRM) in seated and supine positions. RESULTS: Paired t-tests identified small (g = 0.40 – 0.49), but statistically significant (P < 0.05), differences in lnRMSSD data in both the supine and seated positions between both left and right PPG sensors and HRM (Table). Also, trivial (g = 0.07 – 0.09), but statistically significant differences (P < 0.05) in HR data were observed in only the seated position between both right and left PPG sensors and HRM. The PPG sensor tended to underestimate R-R interval length, and overestimate HR and lnRMSSD data, regardless of position. However, weaker associations, and a greater mean bias, were observed in the supine position (r = 0.597 – 0.949; R2 = 0.356 – 0.901) compared to the seated position (r = 0.894 – 0.999; R2 = 0.356 – 0.901) in all metrics. CONCLUSION: Greater absolute and relative agreement between devices was observed in the seated position, even though current HRV data collection guidelines recommend the supine position, with negligible influence of limb side. Future research should examine larger and more diverse sample populations, as well as potential underlying physiological mechanisms regarding greater validity in the seated position.