Arterial compliance probe for cuffless evaluation of carotid pulse pressure

Abstract

ObjectiveAssessment of local arterial properties has become increasingly important in cardiovascular research as well as in clinical domains. Vascular wall stiffness indices are related to local pulse pressure (ΔP) level, mechanical and geometrical characteristics of the arterial vessel. Non-invasive evaluation of local ΔP from the central arteries (aorta and carotid) is not straightforward in a non-specialist clinical setting. In this work, we present a method and system for real-time and beat-by-beat evaluation of local ΔP from superficial arteries—a non-invasive, cuffless and calibration-free technique.MethodsThe proposed technique uses a bi-modal arterial compliance probe which consisted of two identical magnetic plethysmograph (MPG) sensors located at 23 mm distance apart and a single-element ultrasound transducer. Simultaneously measured local pulse wave velocity (PWV) and arterial dimensions were used in a mathematical model for calibration-free evaluation of local ΔP. The proposed approach was initially verified using an arterial flow phantom, with invasive pressure catheter as the reference device. The developed porotype device was validated on 22 normotensive human subjects (age = 24.5 ± 4 years). Two independent measurements of local ΔP from the carotid artery were made during physically relaxed and post-exercise condition.ResultsPhantom-based verification study yielded a correlation coefficient (r) of 0.93 (p < 0.001) for estimated ΔP versus reference brachial ΔP, with a non-significant bias and standard deviation of error equal to 1.11 mmHg and ±1.97 mmHg respectively. The ability of the developed system to acquire high-fidelity waveforms (dual MPG signals and ultrasound echoes from proximal and distal arterial walls) from the carotid artery was demonstrated by the in-vivo validation study. The group average beat-to-beat variation in measured carotid local PWV, arterial diameter parameters—distension and end-diastolic diameter, and local ΔP were 4.2%, 2.6%, 3.3%, and 10.2% respectively in physically relaxed condition. Consistent with the physiological phenomenon, local ΔP measured from the carotid artery of young populations was, on an average, 22 mmHg lower than the reference ΔP obtained from the brachial artery. Like the reference brachial blood pressure (BP) monitor, the developed prototype device reliably captured variations in carotid local ΔP induced by an external intervention.ConclusionThis technique could provide a direct measurement of local PWV, arterial dimensions, and a calibration-free estimate of beat-by-beat local ΔP. It can be potentially extended for calibration-free cuffless BP measurement and non-invasive characterization of central arteries with locally estimated biomechanical properties.

Arterial pressure pulse wave separation analysis using a multi-Gaussian decomposition model

“…WSA using simultaneous measurement of pressure/diameter and flow velocity from the carotid artery has opened avenues for monitoring the effect of rapid physiologic perturbations, such as exercise training (Pomella et al 2018), lower body negative pressure and cold pressor on carotid artery reactivity, distensibility and change in flow and blood pressure. It has also been employed for the reliable measurement of local pulse wave velocity (Joseph et al 2018, Nabeel et al 2018b and central blood pressure (Nabeel et al 2018a.…”

Cuffless Blood Pressure Measurement

“…Combining Equation 1 with the Waterhammer equation (dP/dQ = ρdP/AdA, where Q is the product of area and blood velocity and thus blood volume flow rate) indicates that υ may be computed as the slope of the blood flow rate waveform versus area waveform during early systole wherein wave reflection is minimal (flow-area technique) (116,118). Alternatively, υ may be detected via the time delay between nearby proximal and distal waveforms via ultrasound (119) or another sensor (120). This method may be applied to the aorta or carotid artery and thereby allows measurement of central PP, which is increasingly considered to be of greater clinical value than brachial PP (121).…”

“…This method may be applied to the aorta or carotid artery and thereby allows measurement of central PP, which is increasingly considered to be of greater clinical value than brachial PP (121). This method has been demonstrated in phantom models and against cuff BP in healthy humans (116,(118)(119)(120). However, measurement of SP and DP requires the aid of cuff BP measurements (122,123).…”

An Arterial Compliance Sensor for Cuffless Blood Pressure Estimation Based on Piezoelectric and Optical Signals

“…This model relates PWV to ∆P. As in Equation ( 24), we can estimate the ∆P of the local artery [61] using the PWV, ∆D, D d , and ρ (using 1.06 g/mL) (PP).…”