Is it complete shut down of perception and detachment of physical world? As we know people who stay in coma or unconsciousness "experience" timeless,space-less, absolute emptiness and total detachment from physical world. Even though I used the word "experience" will not suitable to describe the situation in coma or unconsciousness state. It is a condition with no happiness or sorrow, no pain,no darkness or light,no noise or sound etc....and finally we can say "unconditional state of mind." and closer to description of "Nirvana"


what happen when person die during the coma or unconsciousness state? 
Is this similar to Nirvana? (as total detachment of world.)
It is a condition with no happiness or sorrow, no pain,no darkness or light,no noise or sound etc....and finally we can say "unconditional state of mind." and closer to description of "Nirvana"


Actually that's far from Nirvana. If that was the case any sleeping newborn baby would've been in Nirvana without the need for any Dhamma cultivation. A person in a coma might seem to be at peace and without happiness or sorrow, but hidden in those deep layers of his consciousness are still the seeds of defilements, of greed, hatred, and ignorance. As long as these "fuels" are still there and have not been eradicated, the Samsara cycle still goes on for him. In constrast, a person who has attained Nibbana has perfect awareness, but due to the total elimination of all the "fuels", s/he's able to be 100% at peace while being 100% conscious.