Solicitors for a Dublin woman who claim she suffered severe brain damage after an operation will apply to the High Court in London for hospital records.
Ms Philomena Hogan had a heart operation at the Royal Brompton Hospital NHS Trust in London two years ago.
"The operation has a less than one per cent mortality rate but within about six hours of the operation Ms Hogan lay in a persistent vegetative state having suffered a massive cardiac arrest, resulting in severe brain damage," according to solicitors acting for her through her father.
"Ms Hogan, who is 37 years old, cannot now communicate verbally, is blind and has no active movement in her body. It is unlikely there will ever be any improvement in her condition," the solicitors say.
The hospital has not admitted liability.
Ms Hogan is being cared for in an Eastern Health Board institution.
Her parents, who live in Dublin, say a settlement from the hospital would enable them to provide for her future when they themselves are no longer there to care for her.
The family says the hospital has been unable to produce medical records for her operation or for the hours between the operation and the occurrence of the heart attack.
The solicitors are puzzled by the absence of these records because the hospital uses a system "which continuously monitors and records a wide range of medical readings of a patient.
"It is designed to be fail safe, storing data on magnetic tapes with various back-up systems which will print out on a regular basis the numerous readings."
Asked to comment on the statement or on any other aspect of the case, a spokeswoman for the Royal Brompton said it had been advised that the matter was sub judice and she could say "absolutely nothing".
Ms Hogan's father is in poor health and both parents visit her several times a week.
They say she is well-cared for in the EHB institution but they are determined to make provision for her future as she could live for another 30 or 40 years.