Control Method for Continuous Non-Invasive Arterial Pressure Monitoring using the Non-Pulsatile Component of the PPG Signal

We propose a new technique enabling continuous control of transmural pressure using the non-pulsatile (DC) component in the PPG signal as feedback. Photoplethysmograph (PPG) contact pressure has a noticeable effect on blood pressure (BP) tracking, pulse wave analysis and pulse propagation measurements. BP changes alter the difference between intra-arterial and contact pressure, called transmural pressure. Our method is based on keeping the PPG DC component constant by altering the external pressure applied. This way the pressure read from the pressure sensor equals intra-arterial BP. The technology was verified by comparing: (i) measured pressure variation induced by hydrostatic changes with theoretical values, (ii) pulse morphology with and without feedback control during hydrostatic changes, and (iii) continuous MAP readings measured with the reference device (CNSystems CNAP 500) and our device. The proposed technology performed well compared to traditional volume clamp technique while requiring significantly less complex control logic and no fast-switching pneumatics.