Analysis for the non-invasive determination of arterial properties and for the transcutaneous continuous monitoring of arterial blood pressure

Analyses are developed for the procedures of (i) the noninvasive determination of the arterial elastic properties and (ii) the transcutaneous continuous monitoring of arterial blood pressure. Expressions for the pulse wave velocity and arterial pressure are derived, separately, in terms of (1) the nonlinear arterial elastic properties (the coefficients of the strain energy density function), the internal and external diameters of the deformed pressurised artery and the ratio of the unpressurised arterial internal and external diameters, and (2) the nonlinear arterial elastic properties, unpressurised tube diameters and the external diameter of the pressurised artery. It is then shown that if the values of the pulse velocities at an arterial section and of the corresponding arterial diameters are obtained (say, by transcutaneous ultrasonic monitoring) at three instants, then adequate equations are obtained (from the above pulse velocity expressions) which can be solved to yield the values of the arterial properties and the undeformed arterial internal and external diameters. These values are substituted in the expression for arterial pressure, to yield an expression for the arterial pressure, solely in terms of the external arterial diameters. Hence, by continuously transcutaneously ultrasonically monitoring the external arterial diameter, the arterial pressure can be monitored continuously and noninvasively. The feasibility and the required accuracy of making these measurements are currently under investigation.