The sensor used in an oximeter consists of two light sources (red and infrared LEDs) and a photodetector. These components work together to measure the absorption of light as it passes through the tissue, ultimately determining blood oxygen saturation.
Here's a breakdown of the components and their function:
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Light Sources (Red and Infrared LEDs): An oximeter utilizes two different wavelengths of light: red light (typically around 660 nm) and infrared light (typically around 940 nm). Oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (Hb) absorb these wavelengths differently. HbO2 absorbs more infrared light, while Hb absorbs more red light.
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Photodetector: The photodetector is a light-sensitive device (usually a photodiode) that measures the amount of red and infrared light that passes through the tissue (e.g., fingertip, earlobe). The difference in light absorption at the two wavelengths is then used to calculate the ratio of HbO2 to Hb, which provides the SpO2 (peripheral oxygen saturation) reading.
How it Works:
- The red and infrared LEDs emit light through the chosen body part (e.g., fingertip).
- As the light passes through the tissue and blood, it is absorbed by hemoglobin (both oxygenated and deoxygenated).
- The photodetector measures the amount of red and infrared light that reaches it after passing through the tissue.
- The oximeter's internal processing unit analyzes the ratio of red to infrared light absorption.
- Based on this ratio, the oximeter calculates the percentage of oxygenated hemoglobin in the blood (SpO2) and displays it on the screen.
