An inquest into the death of a woman at the Cumberland Infirmary heard how medics "discounted" a crucial indication they had wrongly inserted a breathing tube into her oesophagus.

Mum-of-four Sharon (CORR) Grierson died on November 14.

The inquest, which initially got underway in October, has heard complications arose after medics removed the tube that was aiding her breathing, following surgery in the ENT department.

The tube (ETT) was then wrongly reinserted into her oesophagus twice - an error medics did not immediately spot as they desperately tried to ventilate the 44-year-old charity support worker.

She suffered a cardiac arrest and gave her CPR.

Pathologists said her brain was starved of oxygen for more than 40 minutes, resulting in irreversible brain damage.

Dr Julian Brown, a consultant in anesthesia and intensive care medicine at Southend Hospital, who prepared a report for Cumbria Police, said the key error was the failure to recognise the breathing tube had been wrongly placed.

He said greater weight should have been given to the capnography than the less reliable methods of listening to the chest and clicking, usually indicating the tube is in the trachea.

Capnography represents the amount of carbon dioxide in exhaled air, monitoring ventilation.

Mr Brown told the inquest: "At any stage when capnography gives you any doubt about the position of the tube you should assume it is not in the right place."

He continued: "[Medics] were attempting to provide all the care that was required and they considered a number of possibilities, and they weighted them up, in my view, incorrectly.

"They discounted the possibility that the tube was in the wrong place.

"I don't think they had not thought of the possibility - that the tube was in the wrong place - I think they discounted it."

Giving evidence yesterday, Dr Samuel Chan, core surgical trainee year 2, said he asked if the tube was definitely in the airway.

He said: "I do not remember an absolute affirmative or negative response to my question but I was told by both anaesthetists the tube was in the trachea, but we were not getting a CO2 trace from the capnograph.

"As far as I understand and recall, at no point was there a consistent CO2 tracing."

Sam Harmel, representing Mrs Grierson's family, stated that where the readings are abnormally low, the first thought of an anesthetist is that the tube is in the wrong place.

"I would agree with that statement," said Mr Brown.

Mr Harmel said: "That doesn't seem to have occured in this crisis?"

Mr Brown replied: "That is correct."

Mrs Grierson's procedure, to remove a polyp from her right vocal cord, on November 11, was intended to be a day patient case.

She died in intensive care three days later.

Recommendations in the North Cumbria University Hospitals NHS Trust's serious incident investigation report states capnography should be used as the monitoring tool for use during anesthesia in all areas of the trust.

The inquest continues.