Eli5: how does the finger clip with the laser at the doctors measure my oxygen level?
In: 27
I’m a paramedic.
The little thing is a Pulse Oximeter. It displays your SpO2. SpO2 is the Saturation of partial Oxygen. A red blood cell has a protein called hemoglobin. There are 4 hemoglobin sites on a normal RBC. The oximeter reads the percentage of hemoglobin that is saturated. It uses Infrared light spectrum to assess this not a laser. It also reads the pulse wave in the fingertip.
While in most people, this reading correlates to oxygen levels, but in some cases, the reading is wrong. Any reduction in the blood flow to the finger will give a false reading (cold, having your blood pressure taken on that arm, low blood volume, sickle cell crisis, etc). Any white or visible light in the sensor will give a false reading. Now, Carbon Monoxide will pull oxygen off the hemoglobin and bind itself to the hemoglobin. An oximeter will read 100%, even though your oxygen is depleted. Cyanide prevents oxygen from disengaging from the RBC and blocks O2 from entering the cells. You will read 100%, but will have signs and symptoms of hypoxia (without oxygen).
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