Heart rate variability using photoplethysmography with green wavelength

Cardiovascular diseases are on a continuous rise and the number of people who suffer sudden cardiac arrest. It has been recognized a direct influence between the autonomie nervous system and cardiac activity in the human body. Sometimes causes of disease can be explained by studying the relationship of both parts. Analyzing the beat to beat variations from de cardiac events can show valuable information about the health of the nervous system, which regulates and coordinates the activity of different biological systems. Such variations have been measured and analyzed in the last two decades from studies with electrocardiography (ECG) but in this project is pretended to use photoplethysmography (PPG), as it is a simpler and lower cost non invasive method than ECG. The aim of this project is to develop a prototype for the study of heart rate variability (HRV) based on reflected green light PPG. Equipment was designed with computer support for obtaining the photoplethysmographic signal and processing the information with frequency methods. Results using Fast Fourier Transform (FFT) have shown that photoplethysmographic technique can be used to perform HRV studies. The spectral components in the different ranges established in previous studies demonstrate the expected behavior with PPG, although it is still important to consider other tests and techniques of information processing.