I'm still donig some reseach on hyperventilation. Here is a great graph that show CO2 vs cerebral blood flow.
Note how low CO2 from hyperventilation reduces cerebral blood flow. This is how it is connected to anxiety.
Low CO2 reduces blood flow to all of your cells due to constriction of blood vessels.
I know I keep plugging Buteyko....but by working on reducing hyperventilation is very helpful.