Fotopletüsmograafia

Fotopletüsmograafia, often abbreviated as PPG, is a non-invasive optical measurement technique used to detect variations in blood volume in microvascular beds of tissue. It works by illuminating the skin with a light-emitting diode (LED) and then measuring the amount of light that is reflected or transmitted back. As blood flows through the tissue, it absorbs and scatters light. The pulsatile nature of arterial blood flow causes periodic changes in blood volume, which in turn leads to corresponding fluctuations in the detected light signal.

These fluctuations in the PPG signal can be analyzed to derive various physiological parameters. The most common application is the measurement of heart rate, as the peaks and troughs of the PPG waveform correspond to the heartbeats. Pulse oximetry, a widely used clinical device, combines PPG with red and infrared light to estimate blood oxygen saturation levels. By analyzing the differential absorption of these wavelengths by oxygenated and deoxygenated hemoglobin, pulse oximeters can provide a non-invasive assessment of oxygenation.

Beyond heart rate and oxygen saturation, PPG can also be used to estimate other cardiovascular parameters such as blood pressure, respiration rate, and even detect certain arrhythmias. The technology is employed in a wide range of devices, including wearable fitness trackers, pulse oximeters, and research equipment. While generally considered accurate and reliable for its intended uses, PPG signals can be affected by factors such as motion artifacts, skin pigmentation, and ambient light interference, which may require signal processing techniques to mitigate.