Posted by DocGreg (24.131.169.145) on June 17, 1999 at 23:24:18:
In Reply to: Re: Doc Greg? posted by Bob P on June 17, 1999 at 11:34:45:
Oxygen works for 2 reasons.
1) Increases the amount of oxygen in the blood (obvious)
2) Causes the arteries in the brain to constrict. This is actually a regulatory mechanism that is an integral part of our brain system...trying to get equal amounts of oxygen to all parts that need it.
One of the reasons we feel pain during clusters (and similar with migraines) is that the arteries open up when they shouldn't. Many of the drugs that work against are headaches cause vasoconstriction (Imitrex, ergots, etc). Shrinking the vessels actually increase the rate of blood flow (like narrowing the flow of water from a hose tip). Faster blood flow increases the rate of oxygen delivery to the brain. So, constricting the vessels can actually also increase the amount of oxygenation.
These 2 things increase the amount of oxygen the brain is receiving. Whether it is the increased oxygenation, or primarily the constriction of the vessels that alleviates the pain...I don't think we really know..
Greg