On-Desk Model-Based Study for Evaluating the Effect of Squeezing the Arteries in the Forearm on the Bioimpedance and Pressure of Blood

Abstract

Background. Today, central aortic pressure (CAP) is measured through the invasive procedure of angiography. The only feasible alternative is applanation tonometry, requiring experienced staff to perform reliable measurements. The method of measuring the electrical bioimpedance (EBI) from the wrist gives promising results in estimating the CAP. However, the origin of the EBI data, its quality, and approaches to acquiring the signal are still vague. This study is aimed at determining the dependency of EBI of blood on the diameter, branching, and hindering the blood flow by squeezing the vessel. Methods. An on-desk hydraulic and mechanical pipe system that imitates the arterial tree in the forearm with the modulated flow of saline solution to imitate the pulsating blood was constructed. The setup was verified in the simulation model. The flexible and rigid pipes were squeezed at selected locations of radial and ulnar arteries, and the superficial palmar arc and the pressure with impedance were measured. Results. The multifaceted effect of squeezing the selected locations of arteries in the forearm on the measured EBI and pressure was verified. The effect of arterial stiffening was verified, revealing a very strong inverse correlation of the time-varying impedance ( $\Delta Z\left(t\right)$ ) of rigid pipe compared to the measured data of the wrist. Conclusion. To gain the highest magnitude of $\Delta Z\left(t\right)$ , our research suggests applying pressure on the radial artery and measuring the EBI of the ulnar artery. Our results propose physiology-based suggestions to increase the sensitivity of measured EBI of the pulse wave, constituting a base for designing novel wearable monitoring devices and algorithms for CAP estimation.