There were "lost opportunities" in the care of a premature baby who died after being removed from a ventilator , a coroner has said .
Rohan Rhodes, of Narberth, Pembrokeshire, was born 15 weeks early at Singleton Hospital in Swansea on August 27 2012, weighing 814g (1lb 12oz).
He was placed on a ventilator at the hospital's neonatal intensive care unit, where he was described as "doing well" for four weeks after his birth.
A heart duct which usually closes at birth had remained open and Rohan was transferred to St Michael's Hospital in Bristol for a surgical assessment.
The hospital is part of the same trust as Bristol Royal Hospital for Children, where Sir Bruce Keogh, the NHS's medical director, has ordered a review of children's cardiac services.
Flax Bourton Coroner's Court heard the medical team's plan was to keep Rohan on the ventilator ahead of his upcoming surgery.
But advanced neonatal nurse Amanda Dallorzo took the "autonomous" decision to remove the machine and put a breathing mask on Rohan instead.
Within an hour, Rohan's condition dramatically deteriorated and he developed NEC, a gastrointestinal disease, which required surgery.
Tragically, Rohan never became stable for the operation and he died, aged 36 days, in an incubator at the hospital with parents Alex and Bronwyn Rhodes close by.
Avon Coroner Maria Voisin recorded a narrative verdict following a three day inquest into Rohan's death.
She said three blood gas readings should have been taken to check Rohan's condition but were not, resulting in "lost opportunities" to treat the baby.
"Rohan Rhodes was an extremely premature baby who was at risk of developing NEC," Ms Voisin said.
"He developed this condition which caused his death on September 30.
"On September 29, there were three occasions when he should have had a blood gas test.
"It is not known what results would have been but these were lost opportunities which may have resulted in Rohan receiving earlier medical care."
She told Rohan's parents: "I am very sorry for your loss."
Ms Voisin said the blood gas tests should have been taken directly after Ms Dallorzo removed Rohan from the ventilator, at 4pm on September 29.
A second test should have been taken at 5pm, when it was noticed that a breathing mask placed on Rohan was leaking.
The final "lost opportunity" was after Rohan was put back on the ventilator, at 7.30pm that evening, Ms Voisin said.
Rohan died at 6pm the following day.
Rohan arrived at St Michael's Hospital at 1.55pm on September 28 in a stable condition.
His parents quickly became concerned over his level of care and previously told the inquest feeding tubes were inserted "aggressively" and a nurse did not wear gloves while handling his tube.
Ms Voisin said: "It is clear from the evidence of Rohan's parents that they had a number of concerns with his treatment in Bristol over the next three days."
Dr David Harding, lead clinician at St Michael's Hospital, told the inquest the ward was short-staffed and at full capacity when Rohan was treated.
At 4pm on September 29, Rohan was extubated by Ms Dallorzo - who did not consult Rohan's parents or doctors on the ward - and nurse Suja Thomas.
"Rohan was extubated at 4pm and the ANNP (advanced neonatal nurse practitioner Ms Dallorzo) said it was her intention to check Rohan's blood gas but she didn't as she was too busy," Ms Voisin said.
Rohan deteriorated within an hour.
Dr Vel Ramalingam, the registrar on the ward told how he found Rohan had been extubated and put on breathing mask treatment Continuous Positive Airway Pressure (CPAP).
Rohan's heart was slowing and the mask was leaking, so Dr Ramalingam requested a blood gas from Ms Thomas and that she apply nasal prongs to Rohan.
"In evidence, Dr Ramalingam said he requested a blood gas to be carried out," Ms Voisin said.
"This was not carried out."
Ms Thomas removed the prongs and placed the mask back on Rohan within 30 minutes as he was crying.
At 6.30pm, Rohan became bradycardic as his parents changed his nappy, with his heart rate falling into the 20s at one point.
He was reintubated by 7.30pm.
"The nurse practitioner said she intended to repeat the blood gas but was pulled away," Ms Voisin said.
As Rohan was reintubated, his body temperature dropped to 33.6 degrees - around three lower than normal.
"It later became clear his humidifier has been left off," Ms Voisin said.
His temperature did not recover until 11pm, the inquest previously heard.
Rohan's blood gas had been taken at 1.47pm on Saturday 29 - two hours before he was removed from the ventilator.
It was next checked at 12.13, almost 12 hours later.
Results showed lactic acid and carbon dioxide was building, meaning his condition was weakening.
"By 2.30pm, Rohan was considered to be in circulatory collapse," the coroner said.
"An abdominal x-ray at 5.12 showed a perforation and a consultant was called.
"The surgeon was called at 6am but sadly Rohan was never stable enough for surgery."
Rohan went into cardiac collapse at 4pm that day and required resuscitation.
An hour later, his mother, vet Mrs Rhodes, told doctors to stop resuscitation.
She begged doctors to let him pass away in her arms, but they were unable to remove the lines from his body in time.
He died in his incubator at 6pm on September 30.
Ms Voisin said the cause of Rohan's death should be recorded as acute peritonitis and pneumonia, NEC and prematurity.
Rohan's family are considering legal action following the inquest.
Speaking after the inquest, Rohan's parents said they hoped for "serious systemic change" at St Michael's Hospital.
Mrs Rhodes said: "We would like to thank the coroner for carrying out this investigation into Rohan's death.
"This has been an extremely difficult period for us and we hope by reliving our grief in a public court we have gone some way towards finding justice for our son.
"When Rohan came under the care of St Michael's he was sick but he was a stable little boy. Within 48 hours of that transfer he was dead.
"The coroner found three lost opportunities to investigate Rohan, which may have resulted in earlier treatment.
"Over the course of the inquest, we have heard evidence that the senior nurse was not authorised to remove Rohan from his ventilator and that this act seriously affected his chances of survival.
"We also heard evidence in failings in basic care at the hospital and shortcomings in communications across the unit.
"We can surely all agree that this can no longer continue."
Mrs Rhodes said she and husband Alex, a blacksmith, had not come to the inquest to "demonise" the NHS, nurses or doctors as a whole.
"In speaking publicly about the death of our son, our aim is to see serious systemic change for the better at St Michael's Hospital and the University Hospitals Bristol Trust," she said.
"Rohan suffered greatly in his final hours and we only hope that other children will never have to suffer the way he did.
"We would like to thank the families of other children who have lost their lives at Bristol for their solidarity and support."