Yes you can! A pulse-oximeter only measures the number of red blood cells in circulation that have percentage oxygen that’s bound to them.
So oximeters are not measuring the amount of oxygen in the blood stream, if you have blood that’s saturated with oxygen, notwithstanding the red blood cells.
For example, you can actually saturate so much oxygen in the liquid of your blood, without the red blood cells, that you don’t even need red blood cells if you get to about below 3 ATA which is about -66 feet (20 meters) of sea water.
They’ve done studies looking at this in animals, and they use it in acute trauma settings where you lose so much blood so quickly, or if you’re a Jehovah’s Witness and you don’t want red blood cells or red blood cell transfusions, you can actually temporize people at these deep depths of pressure in a hyperbaric chamber because you’re saturating so much oxygen into the plasma itself.
Now it’s not ideal, obviously, we want to give people red blood cells if they need them, but in acute settings you can really do this.
There’s another example of this, if you get carbon monoxide poisoning.
Carbon monoxide is a molecule that gets stuck on the red blood cell and looks like, if you put a pulse-oximeter on your finger that you’re actually oxygenating well.
But you’re not. You’re actually dying, because that carbon monoxide molecule is not getting unbound from the red blood cell from the hemoglobin molecule and going into your tissue.
So pulse-oximetry is a good way to see how well you’re doing oxygenating your red blood cells, but it’s not a good way to see how well you’re doing from a mitochondrial O2 utilization perspective.
There’s only a few technologies that really allow you to look at mitochondrial PO2 and none of them are very cheap and it’s not an easy technology. Unfortunately, there’s no real easy clinical way to do it right now.
Source: Dr. Sherr, Scott, guest. “How Does Hyperbaric Oxygen Therapy Work?” Biohackers LAB, 8 August 2019. https://www.biohackerslab.com/ep95-dr-scott-sherr/