Heart rate variability and baroreflex sensitivity derived from finger photoplethysmography during dynamic cerebral autoregulation assessments: Association with age, sex and time of day in healthy volunteers

Purpose: Assessing dynamic cerebral autoregulation (dCA) noninvasively includes continuous blood pressure recording with a photoplethysmography device. We investigated in this retrospective study whether, under these standardized laboratory conditions, the Finapress device can provide feasible measures of heart rate variability (HRV) and baroreflex sensitivity (BRS). Material and Methods: Ninety-nine healthy Caucasians [44 women; median age 42 (30-59) years, without cardiovascular risk factors or neurological disease] underwent dCA assessment by simultaneous continuous recording (≥5 min) of cerebral blood flow velocity using transcranial Doppler and fingertip blood pressure using the Finapress device. From the blood pressure signal, systolic blood pressure, heart rate, the inter-beat-interval (RRI), and the power spectral densities of systolic blood pressure and RRI in the low-frequency (LF) (0.07-0.15 Hz) and high-frequency (HF) (0.15-0.5 Hz) ranges were derived. BRS was estimated from the transfer-function LF gain between systolic blood pressure and RRI. Results: Photoplethysmography-derived HRV and BRS indices, as well as the heart rate power spectral density and the LF/HF ratio of systolic blood pressure power spectra, were significantly associated with age. Sex and time of day had negligible influences on the autonomic parameters. Conclusion: During dCA assessment, continuous blood pressure recordings obtained with a photoplethysmography device appear feasible for deriving indices reflecting autonomic nervous system activity. In this setting, these indices were associated primarily with age and should be interpreted as exploratory (not as validated), particularly regarding isolated associations with sex or time of day. Because of potential selection bias, the results may not be generalizable.