Lemmee see if I can apply a bit of KISS here... (my little pea brain likes visuals
)
If we view blood as a river, Hemoglobin is like a boat. There are seats on the boat that carry O2 and CO2 around in the body. Normally, O2 rides the boat from the lungs to the tissues and CO2 rides back. Some O2 and CO2 swim in the river. If there are vacant seats on the boat, O2 and CO2 can climb aboard. CO2 can only come aboard if there are empty seats, but O2 can either take empty seats, or, if there are seats occupied by CO2 then O2 can come aboard and kick CO2 out of the boat. The more CO2 in the river, the more O2 wants to jump into the boat.
The more CO2 in the river the more headache it is.
(1) As depth and pressure increase, PPO2 increases, and there are more O2's in the river, so...
(2) As PPO2 increases, available seats for CO2 to ride out on the Hemoglobin boat are fewer, and...
(3) the more CO2 is in the river, and...
(4) The more O2 is delivered both by boat and river to the tissues, and...
(5) Since having more O2 around allows the muscles to work aerobically more than usual, the muscles can produce more CO2 quicker, so...
(6) The same amount of exercise at depth will cause a quicker higher CO2 level in the blood than at the surface and...
(7) Since anaerobic byproducts of exercise are lower, the diver may not feel the fatigue warnings he/she's accustomed to to slow down and...
(8) CO2 can spike really high and...
(9) more oxygen than just what we'd expect from a direct correlation to PPO2 can get transported to the tissues and therefore...
(10) Oxtox can occur at depth with exercise and subsequent CO2 buildup sooner than it would occur at rest with low CO2 production!
Rick