Session S41.2

Blood Pressure Tracking Capabilities of Pulse Transit Times in Different Arterial Segments: A Clinical Evaluation

C Douniama*, CU Sauter, R Couronne

Fraunhofer Institute for Integrated Circuits
Erlangen, Germany

In recent decades many research effort has been expended in the field of noninvasive, continuous blood pressure (BP) estimation by cardiovascular surrogate parameters, mainly the pulse transit time (PTT). Due to differences in the measurement setup and in the consideration of important physiological aspects (e.g. pre-ejection period of the heart, gradually changing elastic properties along the arterial tree and autoregulation in microcirculatory vessels), however, there is a multitude of inconsistent statements about the BP tracking capabilities of the parameter PTT in literature.
For the purpose of comparing the PTTs on different arterial segments regarding their suitability for central BP estimation – with or without the influence of the above mentioned factors – an appropriate clinical trial has been conducted. With the acquisition of an ECG and the local pulse wave signals of four sequential arterial sites (via photoplethysmography, bioimpedance plethysmography and invasive blood pressure measurement), five observation points and a total of 10 resulting (cardio-)vascular segments can be derived.
Based on 14 valid measurements in 22 ICU patients (approximately 240 hours and 920, 000 heart cycles), the beat-by-beat time series for systolic, mean, and diastolic BP and for the available PTTs have been calculated. After synchronization and data cleaning, every BP-PTT time series combination has been analyzed by linear regression in terms of successive time windows.
The results show that there are significant differences in the suitability of PTT for BP estimation depending on the underlying arterial measurement segment and the influence of physiological aspects. The total mean correlation coefficients of all BP-PTT combinations (averaged over the time windows of all measurements) hereby range from virtually no correlation (R = -0.15) to a medium linear relationship (R = -0.47).

(Abstract Control Number: 189)