Arterial stiffness has been proved to be an important parameter in the evaluation of cardiovascular diseases, and Pulse Wave Velocity (PWV) is a strong indicator of arterial stiffness. Compared to regional PWV (PWV among different arteries), local PWV (PWV within a single artery) outstands in providing higher precision in indicating arterial properties, as regional PWVs are highly affected by multiple parameters, e.g., variations in blood vessel lengths due to individual differences, and multiple reflection effects on the pulse waveform. However, local PWV is less-developed due to its high dependency on the temporal resolution in synchronized signals with usually low signal-to-noise ratios. This paper presents a method for the noninvasive simultaneous measurement of two local PWVs in both left and right radial arteries based on the Fiber Bragg Grating (FBG) technique via correlation analysis of the pulse pairs at the fossa cubitalis and at the wrist. Based on the measurements of five male volunteers at the ages of 19 to 21 years old, the average left radial PWV ranged from 9.44 m/s to 12.35 m/s and the average right radial PWV ranged from 11.50 m/s to 14.83 m/s. What is worth mentioning is that a stable difference between the left and right radial PWVs was observed for each volunteer, ranging from 2.27 m/s to 3.04 m/s. This method enables the dynamic analysis of local PWVs and analysis of their features among different arteries, which will benefit the diagnosis of early-stage arterial stiffening and may bring more insights into the diagnosis of cardiovascular diseases.

Pulse wave velocity (PWV) is a vital bio-indicator of the early cardiovascular diseases. Typically, higher amplitude of PWV indicates stiffer artery. Compared with regional PWV, local PWV is capable of providing a more comprehensive and specific evaluation of artery properties. The main challenge for calculating the local PWV lies in the difficulty in eliminating the multiple reflection effect which induces the change of pulse waveforms during its propagation, consequently the calculation of Pulse Transit Time (PTT) for PWV is highly influenced by the waveform change, which can be referred to as the “intrinsic PTT”, thus leading to the false positive/negative PTTs. This paper presents the Reflection-Immune Featured Segments Cross-Correlation (RIFSCC) Approach, which enables the quantification of the multiple reflection effect. The “steady phase” during the correlation analysis is identified and the “intrinsic PTT” could be consequently eliminated from the actual PTT calculation. Based on the RIFSCC method, the PWV features are derived based on the measurements on 6 volunteers, i.e., lower Body Mass Index (BMI) corresponds to higher PWV amplitudes in general; stronger grip/muscle strength corresponds to lower PWV amplitude; with similar level of difference between left and right grip strengths, higher BMI value corresponds to lower left PWV and higher right PWV. We believe that the RIFSCC method necessitates further investigation with more physiological parameters included on more volunteers with various health statuses, and the analysis of the PWV features will definitely provide more insightful information in clinical applications for cardiovascular diseases.