Application of Photoplethysmography in Blood Flow Measurement

Blood flow measurement has gained much importance over the years as it has a vital role to play in understanding the functionality of heart. There are many principles on which the blood flow measurements are based. This work aims at developing a non-invasive technique for measuring the blood flow using the optical sensors. Among the many optical sensors available, the photoplethysmography (PPG) sensors are capable of measuring blood volumetric changes in the subcutaneous vessels. The proposed method involves acquisition of a real time photoplethysmography (PPG) signal from a reflectance type of optical sensor designed and developed with light emitting diode (LED) as source and OPT 101 as the detector. After the acquisition, the signal is conditioned using appropriate circuitry. The conditioned signal is then displayed on to MATLAB via the microcontroller. The PPG signal so acquired will be analyzed on MATLAB in time domain to estimate the parameters related to heart like the stroke volume which is the area under the curve and the heart rate and thus calculate the blood flow/cardiac output. The proposed method of blood flow measurement is advantageous when compared to the traditional methods of measurement as this is a non-invasive technique and does not require any surgical intervention, it can be used to estimate the blood flow in subjects of different age groups, gender and infants as well.