Ex-paratrooper Mr Alder was taken to hospital after an alleged scuffle
Lessons must be learned from the "tragic death" of ex-paratrooper Christopher Alder, a report by watchdog the Healthcare Commission has said.
It found a failure between hospital staff and police to share information, and called for better co-operation.
Mr Alder choked to death in a police station after he was arrested at Hull Royal Infirmary for an alleged breach of the peace while seeking treatment.
It was published alongside a report of the police's handling of the case.
Mr Alder had been injured in a scuffle outside a hotel in Hull city centre before being taken to the hospital for treatment.
The commission's chief executive, Anna Walker, said the report highlighted "a number of areas of concern".
They included "a failure to pass on key information from the ambulance to A&E staff, and from the A&E staff to the police, and finally from the police to the ambulance staff" in order to help them to make decisions about his treatment, she said.
"There was also confusion about the role of the police in the A&E department, and a lack of understanding from nursing and medical staff about the implications of letting the police take Christopher Alder into custody.
"Mr Alder resisted an X-ray and was discharged into the care of the police without a diagnosis or clarity on follow-up treatment."
Mr Alder choked to death on his own blood and vomit half an hour later on the floor of the police station.
Health care staff "had the best of intentions when treating Christopher Alder", Ms Walker said.
"During interviews, it was clear to us that staff had reflected on their actions and decisions on the night, and had recognised these errors of judgement."
The trusts involved had reviewed plans for discharging patients and accepted the need to draw up action plans based on the commission's recommendations, she said.
- Doctors must confirm and record that a patient treated in A&E considered to be aggressive or difficult is fit for discharge, especially where there is a risk of head injury
- Doctors discharging a patient into police custody must provide a report confirming the fitness of the patient and instructions for the custody officer
- Staff working in A&E must be given guidance and training on the role of the police when called to assist in A&E
- NHS trusts and police forces must agree arrangements for jointly reviewing serious incidents and complaints
- The NHS and police must develop joint national guidance on the management of violent or aggressive patients
Dr Gill Morgan, chief executive of the NHS confederation, said the case highlighted the "challenging issues" involved with information sharing.
"The NHS Confederation is committed to working with the police, the Healthcare Commission and others to ensure we get the right safeguards in place to learn the lessons from this tragic case."