New approaches for rapid setpoint determination and uninterrupted tracking in non-invasive continuous blood pressure monitoring based on volume-clamp method

The volume-clamp method (VCM) is a widely used non-invasive continuous blood pressure (BP) monitoring technique, but determining the volume setpoint (V0) in the open-loop phase can be time-consuming and may cause finger tissue displacement. Additionally, frequent interruptions in BP measurement are required during the closed-loop phase to reset V0. We proposed two new approaches: the proportional value method (PVM) for rapid V0 determination in the open-loop phase and the uninterrupted V0 tracking method (UVTM) in the closed-loop phase. PVM adaptively searches for V0 by analyzing the shape index (Prop) of the plethysmographic (PG) signal under constant cuff pressure, while UVTM introduces a new vascular compliance calculation method in closedloop phase to track changes in V0 without interrupting BP measurement. We describe the non-invasive continuous BP monitor (NC-BPM) based on these methods. Experimental results show that PVM can accurately determine V0, with a mean arterial pressure error of -1.72 & PLUSMN; 2.80 mmHg when compared to oscillometric method (OSCM). UVTM in NC-BPM produced a mean absolute error (MAE) of 2.44 & PLUSMN; 2.91 mmHg for mean arterial pressure (MAP) in induced BP fluctuation test compared to the Nexfin monitor. In the clinical study with invasive reference, the MAE in measuring MAP by NC-BPM was 4.69 & PLUSMN; 5.39 mmHg. Our results show that PVM and UVTM are highly accurate and reliable, with the potential to integrate effectively into VCM-based BP monitoring devices that could benefit patients, healthcare providers, and researchers.

Automated summary

The volume-clamp method (VCM) is a commonly used non-invasive continuous blood pressure (BP) monitoring technique. We propose two new methods, namely the proportional value method (PVM) and the uninterrupted V0 tracking method (UVTM), to address the challenges in determining the volume setpoint (V0) and resetting it during the closed-loop phase. PVM determines V0 by analyzing the shape index of the plethysmographic signal, while UVTM tracks changes in V0 without interrupting BP measurement. Experimental results demonstrate the accuracy and reliability of PVM and UVTM, highlighting their potential for integration into VCM-based BP monitoring devices.