Dysfunction in the microvasculature can lead to insufficient perfusion of tissue and subsequent organ and tissue dysfunction. Studies have linked microcirculation with several cardiometabolic diseases and conditions, including diabetes, hypertension, and macrovascular complications. The skin provides an appealing measurement location for the microcirculation, since it is easily accessible, contains a rich microvascular network and can be used as a proxy measurement for microvascular beds in different tissues. There is an unmet need within the healthcare sector for an easy-to-use, non-invasive and continuous measurement technique for microvascular properties such as the microvascular diameter.
In this project we will develop an optical sensor that uses a combination of blue light and green light photoplethysmography (PPG) signals to estimate the microvascular diameter, enabled by a highly sensitive novel photodetector. Blood pressure is one of the most-often measured vital signs and varies throughout the day. Continuous blood pressure monitoring is crucial for many patients with cardiovascular diseases. The most reliable method of measuring the blood pressure is by using a sphygmomanometer, using an inflatable cuff. Obviously there are many drawbacks using this system for continuous monitoring.
Pulse wave velocity, the speed with which the pulse travels along the arterial wall, has a lot of promise as a proxy measurement used to extract blood pressure. To measure pulse wave velocity accurately with two PPG sensors at a (short) distance from each other, the sampling frequency should be high, as should the timing accuracy of the photodetectors, and the quality of the PPG signal should be very high, which is always influenced by motion artifacts and noise. We will develop a pulse wave velocity sensor using a combination of sensitive and time-accurate detectors to improve the accuracy of PPG-PPG based pulse wave velocity estimation.