The purpose of the project is to build a low cost pulse oximeter and heart rate meter powered by solar energy. The idea based on the fact that the oxygen saturation of blood is one of the most important parameter to be monitored. By make it low cost and solar powered, the device is ideal for developing and under developed nations.
Pulse Oximeter is a non-invasive medical diagnostic device used to detect the oxygen saturation of the blood. Heart rate meter detects the number of beats per minute of the patient, normally referred to as bpm.
Pulse oximeter works on the principal of absorption and reflectance/transmittance of light by multiple components like skin, muscle and blood vessel. Absorption due to tissue, skin or muscle remains fairly constant, whereas absorption due to arterial blood varies. Arteries expand due to the pumping of the heart, expanding the arteries and in turn increasing the tissue between the LEDs and the photodiode, thus increasing the light absorption. Using this principle, heart rate can be detected.
In this project, the pulse oximeter is designed using an infrared and a red LED, projected alternatively on the finger and detection of the transmitted light by a photodiode/phototransistor. The output of the photodiode is given to a transimpedance amplifier, and further amplified and filtered before giving to the Atmega644 microcontroller. The ADC in the microcontroller will convert it into digital form, and later display the value of SpO2 and heart rate on a 16×2 LCD screen.