I am unable to exit the tunnel after getting the defibulator pack at the hospital. Everything is dead, all items have been picked up, but when I get to the tunnel with the wheel handle to exit there is no (A) button to hit which should allow me to exit and go back out. It says mission is complete with the pick up of the defibulator pack. Please Help...

After you get the Defibrillator you can't backtrack all the way to the exit, you have to move through the place and find a door, or wait for a enemy to open a hole on the wall, i don't remember exactly. Go back to the hospital and look around there. If this doesn’t solve the problem, then I suppose that's a glitch.

[Edit} Oh yeah, there's a hit the door-not-opening bug i forgot... I hope you've got a valid save buddy...

You have to practically kiss that door before it allows you to open it. Just walk right up to it until you bump into it.