Influence of Arterial Vessel Diameter and Blood Viscosity on PTT in Pulsatile Flow Model

Abstract

AbstractModelling relation between Pulse Transit Time (PTT) and blood pressure (BP) is a critical step in BP estimation for wearable technology. Recognizing the limitation of assuming constant vessel and blood conditions, we developed a simplified pulsatile flow model to analyze how various factors affect PTT values. Our research focuses on the impact of mechanical characteristics, such as vessel diameter, wall thickness, blood viscosity, and pressure, on PTT measurements and subsequent BP estimation. Measurements were conducted using accelerometer sensors within a custom-designed mock circulatory loop. This setup allowed for the testing of a wide range of pressure values and pulsation rates, as well as the modification of viscosity in blood-mimicking liquids across different vessel models. We employed the Moens-Korteweg conversion model for pressure estimation, initially trained on PTT data from a specific setup parameter combination, and subsequently tested with data from varied setup parameters. We observed high correlation levels (r = 0.93 ± 0.09) paired with high error (RMSE = 163 ± 100 mHg), suggesting potential inaccuracies in pressure estimation. We present the recorded signals and discuss how alterations in physical conditions influence PTT values and the precision of BP estimation.