Question about constriction of prey

I have googled this and I just can't come up with a good enough answer to satisfy my curiousity. What exactly happens to the prey item while the snake is constricting? Does it cut off the oxygen supply and the blood supply thus killing the prey item? Sorry if this is a stupid question but my boyfriend was very curious about this also and I didn't have an exact answer to give him.

The old answer was asphxiation but recent years have brought about new revelations. While asphyxiation can happen, it seems more often than not the prey dies from lack of blood flow before the point of asphyxia. Asphyzia will occur more with larger, more physically resilient prey.

Edit: What he ^^^ said in more wise words than me :rofl:

New research suggest that blood flow is cut before prey have chance suffocate... Heart failure is a the most probably case of death...

I saw a Discovery Channel something-or-other on burmese pythons and they said that the blood pressure of the prey item is increased so much that the animal dies. That might mean that the vessels explode - not sure, just that the blood pressure is elevated above what it can live through.

i heard that it was the prey items inability to take in a breath due to being squeezed & my own observations with feeding nyx.
the snakes wrap around the prey and squeeze tighter every time the prey exhales so it cant take another breath in. after not being able to take in a breath it just falls into unconsiousness & then with continued lack of oxygen its heart stops, which i'm sure is how the snakes know their prey is dead.
thats what happens to us anyways so i hope its the same for them. i think theres no pain in unconsiousness.