Ever Used This Device?

I hope you did use it at some point of your lives. This pulse oximeter measures the oxygen level in blood and also records heart rate. It’s so amazing and thought provoking that such a small device can do such wonders. Let’s see how it does so!

pulse-oximeter

So, the basic principle of pulse oximetry is based on the red and infrared light absorption characteristics of oxygenated and deoxygenated hemoglobin. Oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through. Deoxygenated hemoglobin absorbs more red light and allows more infrared light to pass through. Pulse oximeter uses a light emitter with red and infrared LEDs that shines through a reasonably translucent site with good blood flow.

figure-1-dr-petty-brochure An emitter and photo detector are involved in the transmission and receiving of these LEDs. After the transmitted red (R) and infrared (IR) lights pass through the measuring site and are received at the photodetector, the R/IR ratio is calculated. For example,

  1. a R/IR ratio of 0.5 equates to approximately 100% SpO2,
  2. a ratio of 1.0 to approximately 82% SpO2,
  3.  and a ratio of 2.0 equates to 0% SpO2.

figure_2

References and further reading

http://www.oximetry.org/pulseox/principles.htm

http://www.nonin.com/How-Does-a-Pulse-Oximeter-Work

How pulse oximeters work explained simply.