Pathologists claim that a mum-of-four who was treated at the Cumberland Infirmary died of a lack of oxygen to her brain.

Sharon Grierson was admitted to the Carlisle hospital on November 11 last year for elective surgery to remove a lesion (polyp) on her right vocal cord - a procedure intended to be a day patient case.

An inquest into her death, led by Cumbria's senior coroner David Roberts, got underway yesterday at the Coroners' Court in Cockermouth.

The inquest heard how the 44-year-old, from Aspatria, underwent the procedure that morning under general anaesthetic. She was intubated - where an endotracheal tube (ETT) was inserted into her airway to help her breathing while under anaesthetic - with no problems.

There were also no problems during the procedure, carried out by ear, nose and throat (ENT) consultant Paul Counter.

But complications arose during the ex-tubation process, when the tube was removed.

Dr Alison Armour, consultant pathologist at the Royal Preston Hospital, said in her post-mortem report: "At the end of the procedure, when the anaesthetist tried to extubate her, she suffered complications.

"There was an attempt to re-intubate her but the tube was placed into the esophagus.

"This was removed and there was a second attempt, which again went into the esophagus.

"This was then removed and at the third attempt the endotracheal tube was placed in the airway."

The pathologist told the inquest the three attempts took 45 minutes, during which time Mrs Grierson was "profoundly hypoxic".

"She developed global hypoxic brain injury and was transferred to the intensive care unit where she never regained consciousness and died on Monday, November 14, 2016," she said.

Dr Armour said the anaesthetist attempted to re-intubate Mrs Grierson because her oxygen saturation levels had dropped.

She said after the first two attempts, where it was thought the tube was correctly sited in the trachea, end tidal carbon dioxide was still absent - indicating there was something wrong.

"This lady was in cardiac arrest and was being resuscitated throughout," said Dr Armour's report.

"The tube was finally sited correctly in the trachea but this had resulted in a period of hypoxia - a lack of oxygen to the brain for over 40 minutes.

"This means her brain was starved of oxygen for the significant period, resulting in irreversible brain damage.

"The lady died three days later from the hypoxic brain injury, which in turn occurred as a result of the unrecognised intubation following her elective surgery."

A second post-mortem, by Peter Nigel Cooper, a pathologist at the Newcastle's RVI, echoed Dr Armour's findings and he said his examination had not revealed any alternative explanation for her death.

"All indications are that Sharon Grierson died as a result of hypoxic/ischaemic (CORR) brain injury followed by a prolonged period of mal-intubation," Dr Cooper said in his report.

"Clearly from my post-mortem report I cannot tell that mal-intubation occurred or for how long, but the history as provided to me is compelling. Certainly I could not find any other explanation for the events occurring at the end of the surgical procedure."

He said, however, that any detailed interpretation of where the tube was was a matter of clinical rather than pathological interpretation.

He added that Mrs Grierson was overweight but there was no evidence of natural disease in any of her organs that might have contributed to her death.

Mrs Grierson, who was originally from York, has three sons and a daughter.

Her son Ben and daughter Emily were at the inquest, supported by their aunty Kristie Steele and their grandmother.

Following her death the family said in a statement she was a "cherished mother whose children were her world and who she called her heartbeat".