[Walrus]

In answer to the original question I don't think that hemoglobin is actually the primary carrier for CO2 in the blood, there are at least 3 paths. CO2 dissolves in liquid much more then O2 does so part of it is in the blood plasma and probably other body tissues. You also have the blood buffers ie HCO3, from what I understand this stores more CO2 then what is bound by the hemoglobin.

It makes sense to me otherwise why can you recover blood oxygen so much faster then get your CO2 levels back to resting after a breathold ?
If you look at a pulseoximeter graph of someone doing a breathold, you recover most of your blood O2 in the first 10-20 seconds. It seems to take most people quite a few minutes to feel they are ready to hold their breath again.
Offgassing the CO2 from the HCO3 buffers and from what's dissolved in liquid is a much slower process. I tried to find a reference to it, found something but may not be completely in line with a hypoxic scenario so don't know if those percentages are right, but gives you an idea at least:-



1) 1.5% O2 dissolved in blood
2) 98.5% O2 carried by hemoglobin (Hb-O2)
a) Hb can carry up to four molecules of O2 (four = saturation)
b) Po2 determines Hb saturation
c) also pH, temperature and Pco2 affects Hb-O2 binding
d) ** review O2-hemoglobin dissociation curves for Po2, Pco2, pH & temp.
e) "Bohr effect" describes oxygen unloading (dissociation) where low pH exists
i) enhances oxygen delivery in tissues with increased metabolism
3) 7% CO2 dissolved in blood
4) 23% CO2 bound by Hb
5) 70% CO2 in form of HCO3-


Cheers,
Wal