A Simple Adaptive Transfer Function for Deriving the Central Blood Pressure Waveform from a Radial Blood Pressure Waveform.

Mingwu Gao,David A Kass,Chen-Huan Chen,Ramakrishna Mukkamala,William C Rose,Barry Fetics

doi:10.1038/srep33230

Abstract

Generalized transfer functions (GTFs) are available to compute the more relevant central blood pressure (BP) waveform from a more easily measured radial BP waveform. However, GTFs are population averages and therefore may not adapt to variations in pulse pressure (PP) amplification (ratio of radial to central PP). A simple adaptive transfer function (ATF) was developed. First, the transfer function is defined in terms of the wave travel time and reflection coefficient parameters of an arterial model. Then, the parameters are estimated from the radial BP waveform by exploiting the observation that central BP waveforms exhibit exponential diastolic decays. The ATF was assessed using the original data that helped popularize the GTF. These data included radial BP waveforms and invasive reference central BP waveforms from cardiac catheterization patients. The data were divided into low, middle, and high PP amplification groups. The ATF estimated central BP with greater accuracy than GTFs in the low PP amplification group (e.g., central systolic BP and PP root-mean-square-errors of 3.3 and 4.2 mm Hg versus 6.2 and 7.1 mm Hg; p ≤ 0.05) while showing similar accuracy in the higher PP amplification groups. The ATF may permit more accurate, non-invasive central BP monitoring in elderly and hypertensive patients.

Highlights

O’Rourke and co-workers previously proposed to mathematically derive the central blood pressure (BP) waveform from a radial BP waveform[2]
The adaptive transfer function (ATF) implemented with a purely resistive load yielded central BP waveform estimates that were essentially the same as the ATF implemented with a conventional three-parameter Windkessel load in the training data
We developed a simple adaptive transfer function (ATF) for mathematically deriving the central BP waveform from a radial BP waveform

Summary

Introduction

O’Rourke and co-workers previously proposed to mathematically derive the central BP waveform from a radial BP waveform[2]. Thereafter, some of us showed that this “generalized transfer function” (GTF) could yield good agreement with invasive central BP measurements in cardiac catheterization patients[3,4]. The parameter values are continually re-estimated over time for each subject In this way, in contrast to the GTF whose underlying parameter values are population averages and constant, the new transfer function is able to adapt to the arterial parameters of the subject at the time of measurement. In contrast to the GTF whose underlying parameter values are population averages and constant, the new transfer function is able to adapt to the arterial parameters of the subject at the time of measurement We compared this simple “adaptive transfer function” (ATF) to multiple GTFs using the original patient data that helped popularize the GTF. Our results show that the ATF can offer significant accuracy improvements in the estimation of central BP levels in patients with low PP amplification

Methods

Results

Conclusion