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 non-invasive approaches (e.g., volume clamping, applanation tonometry, 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 paper proposes a method that combines a skin-interfaced pressure sensor with a sensor of pulse wave velocity, to continuously, non-invasively 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 Eartery and Etissue of the artery and tissue, respectively, and the artery thickness hartery and radius Rartery via a single, dimensionless combination, Earteryhartery/(EtissueRartery), i.e., the normalized artery stiffness. This scheme determines 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).
Flexible and wearable capacitive pressure sensor for blood pressure monitoring
