An NHS trust chief executive has claimed the Welsh NHS is not managing to solve the problems staff and patients have been facing for years.
Huw Ross has 'every sympathy with staff and patients'
Huw Ross spoke after an emergency nurse at the University Hospital of Wales e-mailed health minister Brian Gibbons.
The senior nurse said animals would be treated better than some patients.
Mr Ross said the NHS was not configured well enough to deal with all pressures. Dr Gibbons has asked for a detailed analysis of the hospital's problems.
The nurse raised her concerns in an e-mail to the Liberal Democrats after an earlier e-mail to Dr Gibbons went unanswered.
She said patients were treated like "vegetables", patients were left on trolleys for 51 hours and adults were put in paediatric beds.
Staff in the emergency unit were close to despair, she added.
Huw Ross, chief executive of the Cardiff and Vale NHS Trust, which runs the University Hospital, told BBC Wales he could not dispute any of the facts of the email and "wouldn't wish to".
"I feel every sympathy with the staff and the patients.
"I think frustration of the staff is understandable.
"Some of the issues we're trying to deal with have been there on the table for a long time and for whatever reason the NHS in Wales has not managed to solve them," he said.
"The fact is the Welsh NHS is not configured successfully or well enough to deal with all the pressures it is being put under and we're not achieving the standards of service that people have every right to expect."
He called for better capacity and primary care to manage emergency demand.
More than 9,000 people sought treatment at the hospital in December
"We need quicker access to residential home care beds - they are very scarce and getting [more] scarce," he added.
Tina Donnelly, director of the Royal College of Nursing in Wales, said Mr Ross and the new nursing director at the UCW hospital had "inherited a nightmare" and the system needed to be "radically overhauled".
She said she believed the changes in the out-of-hours GP service introduced last October and the failure to recognise that the new walk-in treatment centres that have been introduced in England could help alleviate the problem were factors.
"We're talking about in excess of 9,000 cases arriving at the hospital in December to be looked at. That's an increase of 827 attendances on last year and the year before," said Ms Donnelly.
"If we had sufficient GPs, and if also we had walk-in centres to deal with primary care attendances in A&E, that would allow staff in the A&E departments to deal with trauma and emergency conditions.
"I think that we have to say to the Welsh Assembly Government get on and get some of these centres in progress".
Speaking in the assembly, First Minister Rhodri Morgan said the situation was serious, but normal for the time of years, when there was an increase in respiratory diseases.
Welsh Liberal Democrat leader Mike German said the situation was "unacceptable, not normal".
"No wonder staff are in despair, when the First Minister can see a cry for help, and say this is 'normal for January'," he responded.
Dr Gibbons said considerable work had been done in recent years to tackle emergency pressures.
But he added: "It is important that NHS staff are supported in times of great pressure and this is what the management of Cardiff and the Vale Trust is trying to do.
"Currently 88% of people are admitted to A&E at UHW within 4 hours."
The assembly government has promised to respond to the sister's email, adding it had not been picked up earlier because it was sent to Dr Gibbons' AM account rather than his ministerial one.