As the the title suggests, how is it that a little light they put on our finger when at the doctors/hospital/etc.. is able to tell us our blood oxygen levels?
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The questions already been answering so I’m going to chuck in a fun fact. Because when CO binds to your blood it creates the same colour as O2, if someone has CO poisoning the device will read their blood oxygen content as being normal.
Helpful suggestion for any medical-related question like this – ask your doc / nurse / tech / practitioner / etc. next time someone uses one on you just ask and they’ll explain it.
I’ve got a pretty good Eli5 for this one.
hemoglobins are little molecules that carry oxygen around the blood to the various tissues in the body.
Think of these little hemoglobins as tiny cars (taxis really) each of these hemoglobin cars have 4 seas for oxygen molecules. When they get to their destination the cars empty out and the oxygens goes to work doing their job, but if they’re not needed at that stop, like a buss they’ll just continue onto the next work station and attempt to get off there. AT the end of the journey the hemoglobin taxi travels back to the lungs for more passengers.
Now there are millions of hemoglobin taxis in your body constantly at work. But they don’t always carry 4 oxygen passengers, sometimes less but never more.
The red light in the pulse oximeter looks into the windows of theses taxies and counts, on adverage, how many of the seats are full. If 95% of the seats are full you’re reading will be 95%, of only 80% of the seats are full you’re reading will be 80% and so on.
Now, it’s also important to know that the red light counts how many seats are full in the hemoglobin taxis, but doesn’t count how many taxies are on the road.
This important, because let’s say we have a patient who has had a massive blood loss or is hypovolemic, the light will still read that 90% or 95% of the seats in the taxis are full. Inevitably, the seats will start to empty really quickly and your O2 will drop, but not because you have fewer taxis, just that they’re working harder and can’t keep up (so always put O2 on a patient with a critically low hemoglobin).
The finger light thing can tell how much oxygen is in your blood by measuring the amount of oxygen that is bound to hemoglobin in your blood.
Atoms absorb different slivers of the visible light spectrum. So when light hits an object and bounces back off, some of it is left behind and makes it appear to be a certain colour.
This is how we know the universe is made up of the same atoms here on Earth, and how we know the composition of other planet’s atmospheres just by looking at them through a telescope.
It’s the same concept. The finger device measures the otherwise imperceptible colour of the wearer’s blood
As a Google Product Expert I can answer this.
There are 2 colers of LED’s the Red and Infrared
The amount of Oxygen in the blood affects the absorbtion rate of these two colors.
Since the amount of.. Since the distance also affects the absorbtion rate, most sensor use both colors.
I forget which way the absorption is, I think ocygenated blood absorbs infrared, while deoxonated blood absorbs more red
It’s a pulse oximeter, but I’ll begin lobbying to have the name changed to Finger Light Thing.
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