Transfer-function-free technique for the noninvasive determination of the human arterial pressure waveform.

Alessandro Giudici,Ian B Wilkinson,Michaela Kozakova,Carlo Palombo,Carmela Morizzo,Ashraf W Khir,J Kennedy Cruickshank

doi:10.14814/phy2.15040

Abstract

The estimation of central aortic blood pressure is a cardinal measurement, carrying effective physiological, and prognostic data beyond routine peripheral blood pressure. Transfer function‐based devices effectively estimate aortic systolic and diastolic blood pressure from peripheral pressure waveforms, but the reconstructed pressure waveform seems to preserve features of the peripheral waveform. We sought to develop a new method for converting the local diameter distension waveform into a pressure waveform, through an exponential function whose parameters depend on the local wave speed. The proposed method was then tested at the common carotid artery. Diameter and blood velocity waveforms were acquired via ultrasound at the right common carotid artery while simultaneously recording pressure at the left common carotid artery via tonometer in 203 people (122 men, 50 ± 18 years). The wave speed was noninvasively estimated via the lnDU‐loop method and then used to define the exponential function to convert the diameter into pressure. Noninvasive systolic and mean pressures estimated by the new technique were 3.8 ± 21.8 (p = 0.015) and 2.3 ± 9.6 mmHg (p = 0.011) higher than those obtained using tonometery. However, differences were much reduced and not significant in people >35 years (0.6 ± 18.7 and 0.8 ± 8.3 mmHg, respectively). This proof of concept study demonstrated that local wave speed, estimated from noninvasive local measurement of diameter and flow velocity, can be used to determine an exponential function that describes the relationship between local pressure and diameter. This pressure‐diameter function can then be used for the noninvasive estimation of local arterial pressure.

Highlights

The World Health Organization estimates that ~15% of the population worldwide suffers from high blood pressure, and only 20% of these are effectively managing their condition
Noninvasive estimated carotid systolic pressure (nPs) and estimated carotid mean pressure (nPm) were 3.8 mmHg (p = 0.015) and 2.3 (−17.0 to 21.5) mmHg (p = 0.011) higher than tonometer carotid systolic blood pressure (tPs) and tonometer carotid mean blood pressure (tPm) acquired via tonometry, respectively (Table 1 and Figure 3b–d)
We proposed a new technique where the local wave speed, estimated by noninvasive local measurements of diameter distension and blood flow velocity waveforms, is used to estimate the parameters of an exponential function that allows converting the diameter waveform into a pressure waveform

Summary

Introduction

The World Health Organization estimates that ~15% of the population worldwide suffers from high blood pressure, and only 20% of these are effectively managing their condition. Mean blood pressure (Pm) and Pd and are relatively constant throughout most of the arterial tree (Pauca et al, 2001; Wang et al, 2011), but Ps increases as the measurement site moves distally from the ascending aorta (Reference Values for Arterial Measurements Collaboration, 2014; Segers et al, 2009), most likely due to wave reflections and higher wall stiffness in the distal arteries compared to the aorta. The magnitude of the pressure amplification is age, sex, and pathology dependent (McEniery et al, 2014; Reference Values for Arterial Measurements Collaboration, 2014). Using brachial pressure to estimate pressure in other regions of the arterial tree will generally be poor (Sharman et al, 2017)

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