I think there is a lot of merit to the hypoxia theory. One of the symptoms of my fibro has been a large amount of petichiae all over my body. Petichiae are small red dots caused by broken blood vessels.
I was reading one of the many novels I read while spending my life on the couch with this disease lol, and actually in several of the books I have read they cite petichiae as showing up on a person who has been strangled or had their air supply cut off. Hmmmm.....
Also, I read somewhere else that pain in the extremities in particular is caused by our actual blood cells becoming misshapen and therefore having trouble flowing through permeable membranes. It would not be a huge leap to think that the blood cells responsible for carrying oxygen everywhere would become compromised due to becoming misshapen.