Noninvasive cuffless blood pressure estimation using pulse transit time, Womersley number, and photoplethysmogram intensity ratio

摘要

Objective: Continuous cuffless blood pressure (BP) monitoring research has emerged as blood pressure is one of the dynamic parameters which reflects cardiac arrhythmias and rheological disorders without the drawbacks of current techniques. All the existing measurement techniques are cuff-based with drawbacks such as being discontinuous in nature, being uncomfortable for the patient, etc. Therefore, the goal is to develop an algorithm to estimate BP accurately using the pulse transit time (PTT), photoplethysmogram intensity ratio (PIR) and Womersley number (α) in a noninvasive way. Approach: The PTT technique holds the promise of real-time, cuffless, continuous BP monitoring in clinical settings. However, the non-Newtonian fluid nature of blood is considered insignificant in the conventional PTT model-based BP modeling. In the proposed work, α, representing viscous effects, along with PTT and PIR, is included in the algorithm since it is also one of the parameters that affects the BP. Main results: The proposed algorithm is evaluated with 42 healthy and 39 diseased subjects and compared with the other conventional techniques to evaluate the importance of viscous effects in BP, using performance metrics like mean ± standard deviation, and 95% confidence interval for bias and limits of agreement; a better estimate is achieved with the proposed algorithm. Significance: The proposed algorithm reflects the influences of vasomotor tone and baroflex as well, which makes it suitable for the assessment of BP in both healthy and diseased subjects, with improved accuracy than the current measurement techniques.