A 61-year-old woman died of a heart failure after a four-hour wait in the back of an ambulance meant telltale signs were not spotted by medical staff early enough.
Lyn Brind died at the Queen Elizabeth Hospital (QEH) in King's Lynn having been brought via ambulance after a visit to her GP.
But when Mrs Brind arrived the emergency department at the hospital was too busy to admit her.
By the time she was taken onto a ward she became agitated and short of breath, and was put on advanced life support but deteriorated and died.
Following an inquest into her death, senior coroner Jacqueline Lake shared fears that further people could die under similar circumstances unless more is done to help ease pressure on hospitals.
Her report states that when Mrs Brind arrived at the QEH on May 24 "there was no space in the hospital".
It adds that checks made on her while she waited were not carried out regularly enough, meaning the severity of her case was not clear to the hospital.
Consequently, she was not given high priority for a bed.
During the inquest, Mrs Lake heard that the pressures the hospital was facing had since worsened.
She wrote: "Evidence was heard that at the time of Mrs Brind's death, approximately seven ambulances were waiting to transfer patients.
"At the time of the inquest [on January 5] this had risen to 17 ambulances commonly waiting to transfer."
She added that at the same time the hospital was caring for around 140 patients who were medically fit for discharge.
Helen Blanchard, interim chief nurse at the QEH, said: "Oh behalf of the trust I extend my condolences to Mrs Brind's family.
"We have learned from this case and have implemented the NHS care standards for patients waiting in ambulances, including work with ambulance staff to ensure patients are still seen by a senior doctor if they cannot immediately come into the department and 30-minute observations are completed on all patients while in ambulances."
An East of England Ambulance Service spokesperson said: "In July last year we met with Queen Elizabeth Hospital’s serious incident team to discuss lessons learned and to help prevent this from happening again.
"We have been working closely with all our NHS colleagues to reduce handover delays at hospitals and provide better care for our patients."
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