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Biomedical Engineering

Reflectance Photoplethysmography as Noninvasive Monitoring of Tissue Blood Perfusion

Project Details

Principal Investigator:  Prof P Kyriacou

Researcher:  T Y Abay

Project Description

The assessment of the perfusion of the microcirculation (blood flow, blood volume, blood oxygenation, oxygen delivery/consumption, etc.) has been playing an important role in clinical care and research. There is a continuously growing interest in developing and investigating new instruments for assessing and monitoring blood perfusion. Optical techniques offer the advantages of being non-invasive and they present almost no risks to the patient. Several modalities, such as photoplethysmography (PPG), pulse oximetry (PO), laser Doppler flowmetry (LDF), near infrared spectroscopy (NIRS), and reflectance spectrophotometry have been used in research and clinical settings for the quantitative and qualitative assessment of different tissue perfusion parameters. However, each of these modalities has limitations that did not facilitate their wide use in clinical settings. Among these techniques, only PPG is commonly used in the hospitals for the noninvasive estimation of arterial oxygen saturation (SpO2) by pulse oximetry. However, PPG is mainly used for measuring SpO2 and heart rate, with only few attempts in exploring the capabilities of extracting other physiological information present in the signal. Therefore, this project comprehensively evaluates the feasibility of monitoring other perfusion parameters using the technique of Photoplethysmography. In particular, NIRS analysis is applied to PPG signals in order to estimate haemodynamic parameters other than SpO2 and heart rate. Comparative studies between PPG and other techniques such as NIRS and LDF are carried on healthy volunteers in order to validate the use of PPG for the estimation of other perfusion parameters. New Instrumentation and sensors are also developed to support all in vivo studies.