Single-source PPG-based local pulse wave velocity measurement: a potential cuffless blood pressure estimation technique.

Objective: A novel photoplethysmograph probe employing dual photodiodes excited using a single infrared light source was developed for local pulse wave velocity (PWV) measurement. The potential use of the proposed system in cuffless blood pressure (BP) techniques was demonstrated.

Methods: Initial validation measurements were performed on a phantom using a reference method. Further, an in vivo study was carried out in 35 volunteers (age  =  28  ±  4.5 years). The carotid local PWV, carotid to finger pulse transit time (PTTR) and pulse arrival time at the carotid artery (PATC) were simultaneously measured. Beat-by-beat variation of the local PWV due to BP changes was studied during post-exercise relaxation. The cuffless BP estimation accuracy of local PWV, PATC, and PTTR was investigated based on inter- and intra-subject models with best-case calibration.

Results: The accuracy of the proposed system, hardware inter-channel delay (<0.1 ms), repeatability (beat-to-beat variation  =  4.15%-11.38%) and reproducibility of measurement (r  =  0.96) were examined. For the phantom experiment, the measured PWV values did not differ by more than 0.74 m s-1 compared to the reference PWV. Better correlation was observed between brachial BP parameters versus local PWV (r  =  0.74-0.78) compared to PTTR (|r|  =  0.62-0.67) and PATC (|r|  =  0.52-0.68). Cuffless BP estimation using local PWV was better than PTTR and PATC with population-specific models. More accurate estimates of arterial BP levels were achieved using local PWV via subject-specific models (root-mean-square error  ⩽2.61 mmHg).

Conclusions: A reliable system for cuffless BP measurement and local estimation of arterial wall properties.