blood O2 level and physical exertion

I have made the assumption that a person’s blood O2 content will vary during physical exertion and that it can be measured with that finger clip thingy that shines light through your finger.

Is my assumption correct?

Is blood O2 (or other gas for that matter) affected by exertion, can it be accurately quantified by those finger clip thingies and can you tell if someone is going into an anaerobic state with those things?

I’ve seen those things used for patients in the hospital, but I’ve never witnessed someone on a treadmill using one, and wanted to also know if this is a common measurement when someone is doing a “stress test” during an exam.

Nope, it’s not usually measured during exercise stress tests, because it’s not very helpful.

Most people having MIs will still have oxygen sats above 96%, even though their myocardium is being deprived of oxygen due to blockages in the coronary arteries. Most people on treadmills who have chest pain with exertion will still have normal sats unless they have a lung problem too.

Normal oxygen sats should be above 94% on room air, although people with chronic bad chests can adapt to low oxygen tensions in their blood and sit quite comfortably at less than that. The average person’s oxygen saturation might vary from 100% to 98% during exercise, but that’s probably about it.

Anaerobic exercise refers to which fuel the muscles are burning, the oxygen probe picks up the percentage of oxygenated haemoglobin in the blood. Two very different things. One does not reflect the other, so basically the answer is no to all of your questions- oxygen sats don’t really vary with exercise, they aren’t commonly measured during stress tests and you can’t tell easily if someone is anaerobically exercising with a sats probe.

The content of oxygen in venous blood can drop during exercise but usually does not drop on the arterial side in healthy people whose cardiac output can increase appropriately and whose lungs can maintain normal oxygenation.

Ordinary pulse oximetry just reflects the percent of hemoglobin that is bound to oxygen (or molecules w/ similar affinity for Hb), and only on the arterial side.
It doesn’t say anything about what’s happening at a cellular level which is where anaerobic events take place.

A drop in a Pulse Oximeter reading during all but severe excercise would be considered a reason to do further clinical evaluation.