A former Socceroo who died at an Adelaide Hospital after an oxygen tube was connected to his catheter was left in the care of an unsupervised student nurse, a coronial inquest has heard.

Stephen Herczeg, 72, suffered traumatic internal injuries at the Queen Elizabeth Hospital and died on September 19.

Mr Herczeg, who suffered from chronic lung disease, was taken to the emergency department after a fall and admitted to the general medical ward for treatment of a suspected urinary tract infection.

Registered nurse Waimatai Fiorentino took the stand on Tuesday and admitted that she left a student nurse to conduct hourly observations on patients in the emergency department without supervision.

Ms Fiorentino was also questioned over an entry into the electronic patient record system, known as EPAS, which showed Mr Herczeg was receiving three litres of oxygen per minute while he was in her care, despite doctors instructing otherwise.

The inquest previously heard that Mr Herczeg did not need to be connected to oxygen at all and was undergoing oxygen therapy unnecessarily.

Ms Fiorentino told the court that she did not recall making that entry and the student nurse could have made it while logged in under her username.

Counsel assisting the coroner Naomi Kereru questioned why Ms Fiorentino would allow someone to make entries under her username, describing the practice as "not appropriate" and "irresponsible".

Ms Fiorentino said sometimes nurses entered their notes in EPAS under another nurse's username to save time in logging in and out.

"Sometimes there are not enough computers," she said.

State coroner Mark Johns was scheduled to hear closing submissions on the inquest on Thursday but arrangements are now being made to see whether the student nurse can take the stand.

It was 'possible' the student nurse administered oxygen

During her evidence, Ms Fiorentino maintained that she did not administer oxygen to Mr Herczeg but said it was "possible" the student nurse had.

"I only say it's possible because I wasn't watching her the whole time," she said.

The inquest heard that Ms Fiorentino did not know what symptoms a patient with Mr Herczeg's condition would display if they were receiving too much oxygen.

Doctor Wee Siang Yong, who examined Mr Herczeg in the emergency department, previously told the inquest that high oxygen levels would cause Mr Herczeg to become drowsy and confused.

The inquest has also heard Mr Herczeg was transferred from the emergency department to the general medical ward with nasal oxygen tubes in place after doctors had instructed he not be connected to oxygen.

Ms Fiorentino told the court she assumed the nasal tubes were in place to give Mr Herczeg a "placebo" effect of receiving oxygen.

The court heard Ms Fiorentino could not recall if Mr Herczeg's catheter was connected properly or draining well and assumed the student nurse had checked it correctly.