From Elastic to Viscoelastic: An EEMD-Enhanced Pulse Transit Time Model for Robust Blood Pressure Estimation

2026-04-30

AI Summary

This study addresses the limited accuracy of conventional cuffless blood pressure estimation methods based on pulse transit time (PTT), which often neglect the viscoelastic properties of arterial walls, particularly during rapid hemodynamic changes. To overcome this, the authors propose a physics-informed framework incorporating explicit viscoelastic compensation. The approach employs an enhanced Akima interpolation to reconstruct photoplethysmography (PPG) signals, utilizes an intersecting tangents method for precise pulse onset detection, and applies ensemble empirical mode decomposition (EEMD) to extract high-frequency intrinsic mode functions. For the first time, vascular viscoelasticity is explicitly modeled through a novel “viscoelastic velocity metric” that quantifies damping characteristics. Evaluated on a challenging subset of the MIMIC-II database (364 subjects, 28,525 cardiac cycles), the method achieves medical-grade accuracy with root mean square errors of 5.22 mmHg for systolic and 3.65 mmHg for diastolic blood pressure (R > 0.97), significantly outperforming traditional purely elastic models.

Abstract

Cuffless blood pressure (BP) estimation based on Pulse Transit Time (PTT) has emerged as a promising solution for continuous health monitoring. However, conventional models relying on the Moens-Korteweg equation often fail during rapid hemodynamic fluctuations, as they assume arterial walls are purely elastic and neglect inherent viscoelasticity. To address this limitation, we propose a physics-informed framework introducing a viscoelastic compensation mechanism. First, raw photoplethysmogram (PPG) signals undergo high-fidelity reconstruction using Modified Akima (Makima) interpolation. Second, a robust Intersecting Tangent Method is applied for precise pulse foot localization. Crucially, we utilize Ensemble Empirical Mode Decomposition (EEMD) to isolate high-frequency Intrinsic Mode Functions (IMFs), defining a ``Viscoelastic Velocity Metric'' to quantify the vascular damping effect ($η\cdot \dotε$) typically ignored by elastic models. The framework was rigorously validated on a challenging subset of the MIMIC-II database (364 subjects, 28,525 cardiac cycles) characterized by a high prevalence of hypertension (23.4\%). Experimental results demonstrate medical-grade accuracy, yielding a Root Mean Square Error (RMSE) of 5.22 mmHg for Systolic and 3.65 mmHg for Diastolic BP, with Pearson correlation coefficients ($R > 0.97$). These findings confirm that incorporating viscoelastic features significantly enhances robustness against vascular hysteresis.

Problem

• blood pressure estimation
• pulse transit time
• viscoelasticity
• arterial wall
• hemodynamic fluctuations

Innovation

• viscoelasticity
• EEMD
• pulse transit time
• blood pressure estimation
• vascular damping