Wearable Tissue Oxygenation Monitoring Sensor and a Forearm Vascular Phantom Design for Data Validation

Photoplethysmography (PPG) is a well established method of measuring Heart Rate Variability (HRV) and blood oxygen saturation (SpO2) at the fingers, forehead or other areas of the body where pulsatile flow is present. However, obtaining reliable tissue oxygen saturation (StO2) from optical devices is more challenging due to a number of factors including motion and signal-to-noise ratio. Instrumentation of such devices as miniaturised wearable platforms would allow the device to be worn freely by patients in hospitals or at home. The purposes of this paper are to present: 1) a bespoke, low power StO2 sensor, 2) preliminary comparison to a commercially available photospectroscopy and laser Doppler machine (Oxygen 2 See, Medizintechnik, LEA, Germany) using a pressure cuff forearm ischaemia model, and 3) validation of fluid (blood) flow/relative haemoglobin measurements using a novel forearm phantom.