UC San Diego

Continuous monitoring of blood pressure (BP) from arteries like the brachial artery, carotid artery, radial artery, etc., has clinical significance for a multitude of underlying cardiovascular issues. There are many different ways for BP measurement. The gold standard of continuous blood pressure measurement is cardiac catheterization, which is an invasive method and poses a risk of infections to patients. Other traditional methods like tonometry, photoplethysmography, sphygmomanometer (BP cuff), and an ultrasonic method that measures blood pressure by vessel wall tracking provide conventional non-invasive platforms for blood pressure measurement. However, a sphygmomanometer cannot provide continuous blood pressure measurements, and tonometry, photoplethysmography, and sphygmomanometry are prone to inaccuracies and instabilities. The ultrasonic method to capture BP by vessel wall tracking requires a trained operator to handle the equipment. Due to the equipment's bulkiness and rigidity, it is difficult to achieve stable coupling with the tissue surfaces. A wearable ultrasonic device will help overcome this problem and the difficulties posed by other methods mentioned. A patient-friendly device suitable for clinical use is fabricated, and a blood pressure waveform is acquired from a participant's brachial artery. The fabrication processes of the wearable ultrasonic device are discussed, and additionally, a simple setup to estimate the acoustic impedance of a material is designed to calculate the critical acoustic properties of Ecoflex-0030, like the speed of sound and acoustic impedance. This simple, low-cost experiment will help calculate the acoustic properties of phantoms that are being used for ultrasound research purposes.