If the brain is ever completely inactive (as seen in EEGs) for any length of time, there is no chance of recovery from that state. The body can be kept alive, but the brain is gone and will never have any other activity again.

So, I'm not sure what you mean by "out of oxygen and energy according to any phsysical mechanism" - for any patient who has ever recovered to tell a tale of an NDE, we know for a fact that their brain was constantly producing measurable electrical signals for the entire time.