Police restraint training is still dangerously inadequate eight years after Leon Brigg's death exposed the issue, according to a report by the Befordshire and Luton Coroner Service.
Leon Briggs died on November 4 2013 after being detained under the Mental Health Act and restrained face-down by Bedfordshire Police officers.
The manner in which he was restrained was found to have "more than minimally contributed to his death" the inquest jury found.
The medical cause of the 39-year-old's death was found to be amphetamine intoxication in association with prone restraint and prolonged struggling, with a secondary factor of ischaemic heart disease.
In her report, Report To Prevent Future Deaths, Senior coroner at Bedfordshire and Luton Coroner Service Emma Whitting said people could die because of "insufficient" national guidance for police and paramedics on caring for patients detained under the Mental Health Act.
"It was clear from the evidence heard at the inquest that there remains insufficient or inadequate instruction of both police and ambulance crew about the critical issues of recognising and responding to a medical emergency and the effects of restraint including positional asphyxia," she said.
Ms Whitting said emergency services workers need to be clearly instructed and trained to undertake a risk assessment of mental health patients to ensure they are taken to hospital if needed.
Mental Health Crisis Concordat Strategic Group (MHCCC) policymakers should engage with safety experts to reform the Section 136 Multi-Agency Policy, the report said.
Ms Whitting added that Mr Briggs' death was also precipitated by the fact that officers failed to react quickly when he became unresponsive in the cell.
Summing up expert advice given at the inquest, she said: "Even if action only had been taken at the point that Leon had become unconscious, the relatively simple steps of placing him in the recovery position in the cell and starting CPR whilst awaiting emergency help, on the balance of probabilities, would have resulted in his survival."
"It seems critical that the close monitoring of a detainee who has been subject to restraint should be guaranteed in all cases."