Carotid Pressure Wave Separation Analysis Using Multi-Rayleigh Flow Model

Background: Wave separation analysis (WSA) performed at the common carotid artery (CCA) reveals insights into cerebral vascular pathophysiology; however, the conventional WSA (WSAREF) necessitates the availability of both pressure and flow waveforms measured from the same arterial site. Objective: We propose a method for performing WSA at CCA using a single pulse waveform (WSAm-RAY), by modelling the shape of the CCA flow using multi-Rayleigh curves. The WSAm-RAY reduces the measurement complexity, by modelling the flow waveform shape, targeted at scenarios with limited resources, where comprehensive equipment, specialized personnel and hospital settings are often lacking. The modelled flow was compared with the measured flow for accuracy in modelling the flow morphology. The performance of WSAm-RAY was evaluated by comparing the reflection quantification indices derived from WSAREF and WSAm-RAY. Methods: WSAm-RAY employs weighted and shifted multi-Rayleigh functions, time-optimized for characteristic flow peaks in the early and late systolic phase of the CCA flow waveform. The reliability of the modelled flow and performance of WSAm-RAY were validated on 70 (28 female) participants (age: 20 to 51 years). Continuous recording of CCA flow velocity and diameter waveforms were recorded from the participants. Results: The root-mean-squared-error in forward and backward pressure waves was 2.18 ± 0.97 mmHg (∼ 2.5% of the average mean arterial pressure of the study participants). A statistically significant and strong correlation (r > 0.76, p < 0.001) was observed among reflection quantification indices from WSAREF and WSAm-RAY. Conclusion: WSAm-RAY potentially expands the scope of vascular screenings using a single pulse measurement targeting resource constrained settings.