Some scientist and philosophers have defined death based on the functioning of the circulatory system as a state when there is irreversible cessation of circulation. Since different definitions have been given to explain death, there are several criteria’s that are used to determine death. In case of whole brain damage complete cessation of all clinical functions is a major criterion which could be demonstrated as coma. Similarly irreversible cessation of brainstem functions with absence of brainstem reflexes. Other criteria include absence of any other confounding factors, absence of motor responses, and apnoea. Neurological and cardiopulmonary tests are done to ascertain the death of an individual. In the neurological tests irretrievable brain stem function is determined, while in the cardiopulmonary test irretrievable absence of heart beat and breathing are determined. However, after much debate it has been decided that the cardiopulmonary criteria of death which declares that the heart will not auto-resuscitate and which occurs first is a sufficient enough criterion to declare that a person is dead as it might take some time for the neurological criteria to occur.
b) How do brain death and vegetative state differ? Consider a) behavioral, respiratory (“apnoea”means lack of breathing), b) damage to specific brain structures, and c) brain activity (e.g. EEG, fMRI, PET).
The major criterion for a person to be declared brain dead is presence of coma characterized by irreversible brain damage, while in the case of vegetative state; a person is awake but totally unaware of the surroundings. Such a vegetative state can be partially or totally reversed. However persistent vegetative state cannot be reversed. Brain death can be diagnosed more quickly that irreversible vegetative state as it may take any where between 3 to 12 months depending on the extent of injury to the brain to ascertain vegetative state. Brain dead patients require artificial ventilation