Awake garnered critical praise, particularly for Isaacs' performance.
However, its ratings were low, averaging 4.8 million viewers per
episode and sitting in 125th place in viewership for the 2011–12
season. The series was canceled after one season.
Unfortunately there is no way to tell exactly what was going on here, because the series was canceled after the first season, leaving its mythology mostly unexplained, as no one ardently comes to contest Micheal Britten's situation.
His therapists insist that he is imagining it all to help cope with
the pain. However, when Michael later breaks into Ed's house Ed
admits that he and an accomplice were hiding heroin at the Westfield
Distribution Center; "they decided he had to go", after Michael began
to uncover it.
However, as the show moved towards it's season one finale, Micheal's therapist begins to believe him, as his information from the other reality becomes useful in unearthing the people behind the accident and because Michael begins to remember details from the accident. But that is as close as the show got into proving that he was somewhere else whenever he was sleeping.
One possible explanation they could have come up with was that the character's body might have physically remained in his universe and his consciousness just hijacked the body of his alternate. In science fiction terms this is known as "conscious time traveling" (e.g.: LOST, Fringe). However there is no proof which way anything was happening or how what was happening is possible.