Ms Robertson said she will be writing to the Welsh health minister and NHS Executive.
She described how Mr Abrahams, who had lung cancer, was admitted by GP referral to the Bangor hospital and was increasingly breathless.
He required help to go to the toilet and was on oxygen via a nasal cannula.
North West Wales senior coroner Kate Robertson said Betsi Cadwaladr University Health Board and a health care support worker accepted a side valve ought to have been opened.
A health care worker obtained a portable oxygen cylinder but soon noticed Mr Abrahams had changed colour and rung the emergency bell.
“It appears the oxygen cylinder hadn’t had any oxygen being released,” the coroner said.
The inquest heard that prior to this, Mr Abrahams had been “stable” and treatment for his lung cancer was being discussed.
“It leads me to believe, but for this incident, Jonathan Abrahams wouldn’t have passed away at the time he did,” said Ms Robertson.
The coroner said there had been a “training gap.”
Hospital chiefs said only registered staff would administer oxygen in the future.
Tracey Radcliffe, head of patient safety in the health board, acknowledged there had been another death in similar circumstances just months earlier.
“Following Mr Abrahams’ death we put more actions in place,” she told the inquest.
Pwllheli Sailing Club Commodore Lyndsay Harrold shared a tribute to Mr Abrahams who had been with the club for “many, many years”.
“He has been sadly missed around the place,” she said.
“Jonathan was a very valued member both socially and on the water. He was always happy to help people.”
The health board accepted the coroner’s findings and admitted the care Mr Abrahams received “fell below” the standards expected.
“We have implemented a number of enhanced safety measures as a result in order to reduce the likelihood of this failure being repeated,” a statement said.
BBC News
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