Friday 13 June 2008

How does a pulse oximeter work?

Pulse oximetry exploits a physics phenomenon: oxygenated haemoglobin absorbs different wavelengths of light than does deoxygenated haemoglobin. Actually this phenomenon is really common - the reason that leaves are green is that they reflect light in the 'green' wavelength back to us whilst absorbing most the rest of the light. Bricks do the same, except that for them they absorb most of the 'not-red' wavelengths of visible light, reflecting the remainer and thus rendering them red.

So one would almost expect that deoxygenated haemoglobin absorbs different wavelengths than oxygenated haemoglobin does (technically, it has a different 'absorption spectrum'). And it does. A pulse oximeter fires two wavelengths through our skin - red and infrared, which are each absorbed preferentially by one of the two species of haemoglobin under consideration. When these wavelengths travel through our capillaries, they are differentially absorbed in a ratio that corresponds to the ratio of oxygenated to deoxygenated haemoglobin. A computer does the calculations, and gives you the arterial saturation of the blood.

Hope I got the physics right! Clever, isn't it?

7 comments:

  1. Quickly measure your oxygen saturation (SpO2) and pulse rate with Santamedical SM-165 Pulse Oximeter that delivers matchless accuracy & easy to operate. Buy Now at Santamedical.com
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  2. Self-adjusting finger clamp plus simple one-button design allows for easy operation. Small portable size makes it easy to handle and carry. Buy Now at Amazon.com
    Fingertip Pulse Oximeter

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  3. I am pleased with its performance and how user-friendly it is. The display is brightly lit and very readable. I can check my oxygen saturation and heart rate instantly. The resolution is excellent and I can see on a graph the strength of my pulse graphically. Buy Now at amazon.com
    Santamedical Fingertip Pulse Oximeter

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  6. The easiest way to monitor your heart beat & oxygen saturation & temperature with Pulse Oximeter Pulse Oximeter

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  7. A pulse oximeter is a medical device that indirectly monitors the oxygen saturation of a patient's blood (as opposed to measuring oxygen saturation directly through a blood sample) and changes in blood volume in the skin, producing a photoplethysmogram.

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