Evaluation of a multimode photoplethysmographic sensor during cuff-induced hypoperfusion

Photoplethysmography (PPG) is a technique widely used to monitor volumetric blood changes induced by cardiac pulsations. Pulse oximetry uses the technique of PPG to estimate arterial oxygen saturation values(SpO₂). In poorly perfused tissues, SpO₂ readings may be compromised due to the poor quality of the PPG signals. We have developed a new multimode PPG measurement system which utilizes a reflectance PPG probe that operates in reflectance, transmittance and transreflectance mode simultaneously aiming to improve the quality of the PPG signals in cases of poor peripheral perfusion. In order to evaluate the performance of the probe, experiments were performed in healthy volunteers. A blood pressure cuff was used to induce systematic and controlled artificial hypoperfusion while PPG signals were recorded using all three modes. It was found that the amplitude of the transreflectance signal was significantly greater than the other two conventional PPG sensors at all occlusion pressures, suggesting the potential for improved signal acquisition in patients with peripheral hypoperfusion.