Woman describes how hospital treatment caused hallucinations
It is a condition which is rarely talked about and most people are too embarrassed to mention it after they recover.
Little is known about critical care delirium, or ICU psychosis, which triggers psychological effects in patients in intensive care.
During delirium some patients believe doctors are trying to kill them, they see ghostly figures, suffer hallucinations and anxiety.
Most patients recover quickly with the correct help.
A recent study found that some 55% of people who survive intensive care treatment go on to develop psychological disorders like depression or post-traumatic stress disorder.
Frances, who did not wish to give her surname, was in intensive care in the Royal Victoria Hospital in Belfast for four weeks following complications during her second heart bypass.
She had never heard of critical care delirium.
"When I became aware, firstly, I had terrible hallucinations. Other patients were not in their beds, they were in pop-up cars. There were people dressed as ninjas at each side of the bed.
"I felt they were going to harm us and we had to be good. Looking back now I believed they were trying to kill us and they did it by injecting your stomach.
"On one occasion, I even hid in a cupboard to try and stop them killing me.
"When my family came to see me I was begging them to take me home and told them if they didn't take me home I would be killed that night. I started to text people and tell them to come and get me. It was worse for my family knowing I was so unhappy," she said.
"It would be reassuring for families to know that it is actually a condition and it's not just happening to you.
"You do feel very embarrassed about it and you don't want to bring it up because you feel so embarrassed."
A recent study of 157 patients at University College Hospital, in London, found high levels of depression, anxiety and post traumatic stress disorder.
Dr George Gardiner, a clinical lead at the Critical Care Network in Belfast, has been studying critical care delirium. He said the condition is not unusual.
"The symptoms are caused by the environment and the critical illness suffered. They are upsetting and unsettling for the family and friends who will also see what is going on. It is something we in the intensive care unit have been concentrating on for the last ten years," he said.
International research has been focused on trying to improve how to spot the symptoms to treat the condition and the Critical Care Network has developed a number of scoring systems to try and pick it up at the earliest stage in patients.
"There are a series of cognitive tests to see if a patient is in the zone of delirium and that is what Frances has been experiencing, a condition called critical care delirium.
"There are a number of strategies which can be used to try and normalise the environment. Introducing night and day when that can be done, reducing sedation when possible and freeing patients from the equipment. That's something that we are trying to push forward here in Northern Ireland."
Dr Gardiner explained that, by definition, a patient in intensive care has a critical condition and that it is not surprising that the brain starts to malfunction in this way.
'We can treat this'
He understands how patients can begin to slip into delirium.
"By the very nature of the monitoring we have to do and the equipment that is needed to support your organ systems night and day it can be difficult to differentiate, there can be noises, there are alarms and there is always a stranger, albeit a nurse in the room with you," he said.
"Never the less it is quite common for patients, especially the more critical patients, to lapse into delirium and sometimes it can be quite difficult to pick that up."
Dr Gardiner has been involved in trying to reduce the chances of patients suffering from delirium.
"The strategy we employ in NI is to have the patient as lightly sedated as possible and move them out of intensive care as soon as possible. We are having good success at this.
"We never get the opportunity to let people know that delirium is a common effect of being in critical care and we are looking out for it and we can treat it. Most people will make a good recovery. It might take a bit of time but patients should be assured we are on top of the issue.
"We can treat this and people will get back to normal."