There is a bit more going on with CO poisoning than just the bond between CO and hemoglobin, but here is a simplistic explanation on what is going on in the body:
When CO is inhaled one of the things that happens is it forms carboxyhemoglobin in the red blood cells. The half-life of this bond is cited as approximately 320 minutes when breathing air, 74 minutes when breathing 100 O2 and further decreased to 23 minutes when 100 O2 is coupled with hyperbaric treatment at 3 ATA. The 100 O2 hyperbaric therapy dramatically reduces the half-life of caboxyhemoglobin and significantly aids the body's ability to regain normal O2 levels. As the bonds that bind the CO to the hemoglobin break down some CO is exhaled and the rest is broken down by oxidative metabolism and then filtered from the blood and otherwise eliminated from the body.
Here is an article that has some details:
Hyperbaric Treatment Of Carbon Monoxide Toxicity - StatPearls - NCBI Bookshelf
"The mechanism of action of HBO2 is not only to cause more rapid displacement of the CO from hemoglobin and generate normal oxyhemoglobin in the red blood cell, but the oxygen delivery to the tissue is also increased by the oxygen that is dissolved in the plasma. The other benefit of the HBO2 is to reduce the adherence of neutrophils on the damaged endothelium of the blood vessels in the brain, which reduces tissue edema and reduces the lipid peroxidation. The extra oxygen that is delivered to the tissue also helps to reduce the CO bound to the cytochrome proteins in the mitochondria of the cells and contributes to restoring oxidative phosphorylation, which neurons are especially dependent upon for normal function and survival from the ischemic insult."
Carbon monoxide poisoning
"The mainstay of treatment is 100% oxygen administration until the carboxyhaemoglobin level is normal. On this regimen the half-life of carboxyhaemoglobin is 74 minutes (compared with 320 minutes breathing air)
16,
23. Lactic acidosis facilitates tissue oxygen diffusion and should not be corrected unless extreme (pH<7.15)."
and
"Hyperbaric oxygen has many benefits. The half-life of carboxyhaemoglobin at 3 ATA (absolute atmospheres) of oxygen is only 23 minutes
27. Other benefits are improved mitochondrial function, impairment of platelet adhesion in the capillaries and inhibition of lipid peroxidation"
Another good resource:
https://www.atsdr.cdc.gov/ToxProfiles/tp201-c2.pdf
-Z