Measurement of Blood Pressure via a Skin-Mounted, Non-Invasive Pressure Sensor

Abstract

Traditional methods to measure blood pressure are intermittent and may fail to detect the critical blood pressure fluctuations. Continuous blood pressure monitoring offers important clinical value in predicting cardiovascular diseases. Invasive (i.e., artery cannulation) and noninvasive approaches (e.g., volume clamping, pressure sensor, ultrasound, and optical methods) have limitations that prevent their generalized use outside of controlled settings, and few account properly for changes in the properties of the arteries (e.g., after drug administration, aging). This article proposes a method that combines a skin-interfaced pressure sensor with a sensor of pulse wave velocity, to continuously, noninvasively, and accurately measure the blood pressure, in ways that eliminate drifts and other artifacts that can prevent accurate, longitudinal monitoring. A scaling law is established to show that, for a linearly proportional relationship between the blood pressure and sensor pressure, the coefficient of proportionality depends on the elastic moduli E-artery and E-tissue of the artery and tissue, respectively, and the artery thickness h(artery) and radius R-artery via a single, dimensionless combination, E(artery)h(artery)/(EtissueRartery), i.e., the normalized artery stiffness. This scheme determines the blood pressure in a manner that explicitly accounts for changes in the artery elastic modulus and thickness (e.g., due to the administration of drugs, aging).