A high-dependency patient died after the power supply to her ventilator cut off and the battery drained, an inquest heard.

A loud 'screeching' alarm sounded when the ventilator keeping Jacqueline Scott breathing finally ran out of batteries.

But a nurse did not recognise the sound as no ventilator had ever made that noise.

Mrs Scott, 54, died later in the Richmond ward of St George's Hospital in March 2015.

A jury inquest at the Royal Courts of Justice heard Mrs Scott was on a ventilator plugged into a wall socket, but the circuit providing it power had blown, meaning it was running on batteries.

It ran down and several alarms rang out before power cut off.

Mrs Scott's call bell was also faulty at some point.

Dr Renate Wendler led the investigation into Mrs Scott's death.

She told a jury of six men and three women: "We looked at Mrs Scott's health and we found she was very sick and probably a pre-terminal patient when she came to the hospital.

"We found evidence of good practice and care.

"Usually if an incident happens, it is a result of a lot of factors, no single factor.

"Nurses were very busy looking after her in all sorts of ways."

Dr Wendler, who is a consultant anaesthetist, said the best nurses were looking after Mrs Scott, but that they reviewed the design of the machine and felt it was "not intuitive".

She said: "I do not think the delay in calling for help had anything to do with the outcome of Mrs Scott's case.

"The call bell, at some point, must have been faulty, but nursing staff was not aware.

"Not all power supplies in the trust are uninterrupted, this one failed because it was interrupted."

Dr Wendler said it was "not realistic" to expect nurses in the ward to know when power would have been interrupted to the plug sockets.

She told the jury: "The machine made a loud screeching alarm that no nurse had previously heard.

"This noise must have been the final battery warning.

"A lot of alarms had sounded on the machine.

"They were high priority alarms."

Mrs Scott's son said: "We do appreciate everyone involved in my mum's care.

"We are really grateful for the effort that all the staff put towards my mum's care."

Changes have been made to the way nurses' training is recorded at the hospital following the incident, to ensure it is clear whether nurses have received 'on-the-job' training or formal training for a piece of equipment.

The estates department now has a log of jobs that may have been interrupted, so that works are finished.

The level of power supply may be increased in the ward, even though the current level meets mandatory standard.

The jury returned a verdict of death by natural causes.