**TRIGGER WARNING! Don't read while driving, may cause sleepiness.**
The SpO2 shows the % of red blood cells carrying oxygen to the cells. The finger thingy shines a red light through your fingernail ( earlobe, nares, forehead, toes. When you can't get a good reading you will try anywhere!) and measures the difference coming out.
Remember arterial blood is brighter red than venous. They use an algorithm to give a reading. If it on a monitor, it may also show your pulse. This should be a smooth waveform and roughly match your heart EKG tracing.
Higher is better (usually). 97 to 100% being Great. 94% Okay. 85 to 94% lets get concerned. Less than that, we need to get an ABG (arterial blood gas). (These are rough numbers and a lot of other things have to be factored in.) This 'blood test' gives the best information on how your breathing. The Rn, Respiratory Therapist, and MD will look at the results and decide what needs to be done next. It gives SpO2, Ph, CO2, PaCO2, and HCO3

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