Understanding Theory
Week 1 - Wednesday
July 18, 2018
Discussion:
This project is based on the principle of PPG which is a non-invasive method of measuring the variation in blood volume in tissues using a light source and a detector. Since, the change in blood volume and heart rate synchronous to the blood glucose concentration, this technique can be used to measure the blood glucose concentration in blood. Transmittance and reflectance are two basics types of PPG. For the transmittance PPG, the light source is emitted through the tissue and being detected by the photodiode to measure the resultant light. The limited penetration depth of light through the tissue causes the transmittance PPG is applicable to a restricted body part, such as the finger and earlobe.
The following figure above shows a basic reflectance PPG probe to extract the pulse signal from the fingertip. In the reflected PPG, the light source and the light detector are both placed next to each other. Thelight is emitted into the tissue and the reflectance light is measured by the detector. As the light does not penetrate the body, the reflected light can be applied. In either cases, the detected light reflected from or transmitted through the body part will fluctuate according to the pulsatile blood flow caused by the heartbeat. The blood glucose consentration in blood can be measured due to the heart rate reading.
Conclusion:
A subject's finger is illuminated by an IR LED. Light is absorbed, depending on the tissue blood volume. Consequently, the reflected light intensity varies with the pulsing of the blood with heartbeat. From the value gained, the blood glucose level can be determined.
July 18, 2018
Photoplethysmography (PPG) Theory
Objective: To briefly explain the theory behind the development of the Optical Based Non-invasive Blood Glucose Monitoring Devices.Discussion:
This project is based on the principle of PPG which is a non-invasive method of measuring the variation in blood volume in tissues using a light source and a detector. Since, the change in blood volume and heart rate synchronous to the blood glucose concentration, this technique can be used to measure the blood glucose concentration in blood. Transmittance and reflectance are two basics types of PPG. For the transmittance PPG, the light source is emitted through the tissue and being detected by the photodiode to measure the resultant light. The limited penetration depth of light through the tissue causes the transmittance PPG is applicable to a restricted body part, such as the finger and earlobe.
Transmittance PPG(left) and Reflected PPG(right)
Conclusion:
A subject's finger is illuminated by an IR LED. Light is absorbed, depending on the tissue blood volume. Consequently, the reflected light intensity varies with the pulsing of the blood with heartbeat. From the value gained, the blood glucose level can be determined.