It is "implausible" an elderly man connected his own oxygen tube to his catheter causing a "cruelly painful death", but it could not be ruled out, a South Australian coroner has found.

Former Socceroo Stephen Herczeg, 72, died after his bladder burst and his lungs collapsed at the Queen Elizabeth Hospital (QEH) last September.

South Australian Coroner Mark Johns said the most pressing issue in the inquest was to answer the question of how the oxygen supply came to be connected to Mr Herczeg's catheter.

He said although there was evidence Mr Herczeg, who was in a confused state, had been known to fiddle with his catheter tubing on a previous hospital visit, it was a very complex mechanical task to rearrange the tubes in such a way.

"It is clear this event could only have occurred by human agency," the coroner said.

"The possibilities are that Mr Herczeg himself effected these manoeuvres or that they were done by the hand of another person.

"In either case, I am of the opinion that the process would have taken two hands in order to avoid pain that would have either caused Mr Herczeg to protest if the manoeuvre was being undertaken by someone other than him, or that would have caused him to desist if he was doing it himself."

No evidence to support deliberate mix up, coroner says

Mr Johns said it would be "very unlikely" a member of the nursing staff would have accidentally mixed the connection due to the complexity involved, and there was no evidence anybody else had come into the ward and done it.

He said it was "abhorrent" to think someone would have done it deliberately, and there was no evidence to support such a theory.

"I am reluctant to reach the conclusion that Mr Herczeg did this to himself because of the complexity of the task and the multiple manoeuvres," he said.

"However, I cannot exclude the possibility that he did it himself, implausible as it seems. I therefore find that the tubing was interfered with by an unknown person."

Mr Johns described Mr Herczeg's death as "horrific".

"In the awful and macabre circumstances of Mr Herzceg's death his body filled much like a balloon, causing internal disruption," he said.

"The pressure of the gas prevented him from being able to fill his lungs and he died because he could not breathe."

The inquest heard there was evidence Mr Herczeg was "yelling and screaming" before he was discovered in a state of collapse by hospital staff.

"It goes without saying that this event should not have happened," he said.

Nursing staff put Herczeg on 'set and forget regime'

The inquest heard Mr Herczeg, who had chronic lung disease, was admitted to hospital by ambulance with a suspected urinary tract infection and was initially cared for in the emergency department before being moved onto a ward.

Mr Johns criticised the level of care and supervision provided to Mr Herczeg and incomplete admission notes on an electronic filing system known as EPAS.

Former Socceroo Stephen Herczeg in his playing days. ( Supplied: The Advertiser )

"Mr Herczeg's death by this appalling mechanism was cruelly painful," Mr Johns said

"It was entirely preventable, at least on the assumption that nobody connected the tubing with the intention of causing his death.

"It is clear that if Mr Herczeg had not been on oxygen his death would have been prevented."

Mr Johns criticised the lack of oversight, saying Mr Herczeg was left in a confused state for hours without being checked on by medical staff and his oxygen regime may not have been necessary for all of that time.

"In effect, Mr Herczeg was put on a set and forget regime with respect to his oxygen supply," Mr Johns said.

"It is plain to me that the nursing staff responsible for his care ... did not provide an adequate level of care and supervision to Mr Herczeg.

"Had they done so, this tragic event would not have occurred."

Mr Johns' recommendations included ensuring admitting doctors provide detailed instructions to staff on respiratory patients not admitted to a respiratory ward, "leaving no room for error".

There was also a recommendation a risk assessment be conducted on patients exhibiting confusion before they are admitted to a ward.