[cordonbleu]

there is a complication, this is not all about solution chemistry, this is a biological system that uses molecular affinities to transport O2 and CO2. A propertiy of any transport chain is lowest affinity at source of substance, highest affinity at destination. the overall efect is that small variences in atmospheric O2 have a large effect at the lung surface where the lowest O2 affinity occurs. This also is sensative to the promiscuity of haemoglobin, having affinity for BOTH O2 and CO2

kneejerk link below V

http://bio1520.biology.gatech.edu/nutrition-transport-and-ho...

https://en.wikipedia.org/wiki/Oxygen%E2%80%93hemoglobin_diss...

www2.hawaii.edu/~moeng/Web_Zoo142/Lecture Notes/Zoo142ch23.pdf [PDF]