Plot hole: The system providing oxygen can only be accessed by someone slim. Therefore John Goodman built the bunker with him unable to access the key facility that provides oxygen in his bunker. Yet he must have been able to go and get Britney when she went to that area?
Continuity mistake: Michelle ends the phonecall in her car at 6:27pm. When she regains consciousness in the bunker it's 6:29pm. Either she was retrieved from her crashed car, taken to the bunker, chained up and hooked to an IV in 2 minutes (impossible), or she's been unconscious for exactly 24 hours, which would be a sign of a serious brain injury (with no other symptoms). Either way something's not right.