In vivo evaluation of human calf blood pressure by using different external compression strategies

Objective. Calf blood pressure plays an important role in various clinical applications, such as determining the appropriate cuff pressure for compression therapy and diagnosis of lower extremity vascular diseases, which necessitates the integration of built-in measurement methods within the device. This study aimed to investigate the differences in human calf blood pressure assessments resulting from the application of various in vivo external compression strategies. Approach. An experimental procedure incorporating different compression strategies, specially the low-pressure-sustained mode, the slow-inflation mode and the slow-deflation mode, was conducted to capture the dynamic responses of the photoplethysmography (PPG) signal for calf blood pressure evaluation. Nineteen subjects, including 13 males and 6 females, participated in this experimental study. Feature points related to calf blood pressure were extracted from dynamic responses of the PPG signal and subjected to statistical analysis. A lumped parameter model of the human lower extremity was developed to assist in analyzing the biomechanical factors underlying these differences. Main results. The experimental results indicated that the dynamic behaviors of the PPG signal followed clear and consistent patterns, and the calf blood pressure value derived from the PPG signal in the slow-inflation mode was significantly higher than that obtained in the slow-deflation mode. Model simulation results showed that the differences in the evaluated values of the calf blood pressure between the slow-inflation and slow-deflation modes were caused by the different collapse processes of calf arteries and veins. Significance. This study could help understand the forced collapse process of blood vessels in the calf and inspire new ideas on calf blood pressure evaluation and personalized compression therapy.