The detailed data obtained by Fairfax Media shows high rates of isolation and restraint at Sydney's children's hospitals and huge variations across the state's hospitals.

It documents the use of seclusions and restraint at every mental health unit in NSW hospitals every six months between 2008 and June 2016.

The average duration of seclusion episodes at the Children's Hospital Westmead from January to June 2016 was 38 hours, the InforMH data compiled by the NSW Ministry of Health shows.

The number of children kept in seclusion at the hospital is low, but even one case of such prolonged isolation was "extremely distressing" considering the psychological trauma and risk of physical injury inflicted on patients, said psychiatrist Dr Ian Hickie, National Mental Health Commissioner.

The Sydney Children's Hospital Network (SCHN) - comprising the Westmead and Randwick-based children's hospitals - had one of the worst rates of seclusion in the state (11.3 per 1000 bed days).

More than one in 10 hospital stays at the acute units of SCHN involved physical restraint.

Sydney Children's Hospital at Randwick had the highest rate of physical restraint of any NSW acute unit (57.8 episodes for every 1000 patient bed days).

The Health Ministry publicly reports state and local health district seclusion and restraint rates in its annual reports, but public hospital psychiatrists and patient advocates have been demanding this level of detailed data be publicly available and updated regularly to hold to account the state's mental health units to account and reward those who eliminate the practice.

The calls intensified with the release of horrific CCTV footage showing the death of mental health patient Miriam Merten after she was locked, naked, in a seclusion room with no water and covered in faeces at Lismore Base Hospital.

"This data should be published monthly. We should all be able to know what's going on. It is a fundamental human rights issue," Dr Hickie said.

"Anyone we fear, in mental health, is being locked up. We don't treat patients like this in any other treatment setting," he said.

NSW Chief Psychiatrist Murray Wright said the high rate of seclusion and restraint among children was concerning, and NSW Health had made a concerted effort to reduce rates, including calling in US experts in 2012 to train staff.

Tasked by the NSW health and mental health ministers to conduct a six-month statewide review of restrictive practices, Dr Wright said the 38-hour average was an aberration in the context of the children's hospital's trending data that otherwise showed very low average seclusion duration over the past eight years.

"[My guess is] there was something extraordinary in that unit happening at that time," Dr Wright said, suggesting there were likely "one or two particularly challenging patients".

He cautioned against drawing conclusions from one data point, but said "ultimately the buck stops with us".

"We need to make sure that these circumstance [are] extremely rare and we have to create a system that can cope with this extremely rare situation," he said.

"We need to approach this in a way that doesn't put patients at risk of harm in other ways."

More than 40 hours in seclusion

Richmond Clinic in Lismore had the longest seclusion episodes of any NSW acute facility, averaging 41 hours. Roughly two-thirds of hospital stays involving seclusion at Richmond Clinic involved patients left in seclusion for more than four hours.

South East Sydney LHD - encompassing Prince of Wales Hospital, St George and Sutherland hospitals - had the second-highest physical restraint rate in NSW behind the children's network (26.8 per 1000 bed days).

The St Vincent's Hospital Network's Caritas acute unit had the third-highest rate of restraint among LHDs, with 9.3 episodes per 1000 bed days.

The data shows a significant decline in restrictive practices in the past five years.

"But it hasn't happened as quickly as we'd like or to levels we'd like to see," Dr Wright said.

Some 7.3 per cent of stays at acute units involved seclusion in July to December 2009, dropping to 5.6 per cent in January to June 2016.

But the average time patients spent in seclusion has almost doubled since 2008, from three hours to 5.6 hours in January-June 2016.

More than one-third of admissions to an acute mental health ward in NSW involved patients left in seclusion for more than four hours.

There had been were marked improvements at individual hospitals. Royal North Shore, which had a peak seclusion rate of 17.1 in July to December 2009, had dropped to 2.3 in January to June 2016, one of the lowest in the state.

Goulburn's seclusion rate also dropped, from a peak of 18.5 in July to December 2008 to 2.9 in the first half of 2016.

'Cellblocks in hospitals'

In 2005, Australian government ministers and healthcare practitioners agreed the restrictive practices should be eliminated, acknowledging they infringed on an individual's freedom and rights.

"More than a decade later we're still seeing high rates of this extremely distressing practice," said Dr Hickie, who is also co-director Health and Policy of the Brain and Mind Centre at the University of Sydney.

"There is no way to justify this continued practice when it causes such psychological trauma to patients.

"Fundamentally, building cell blocks in hospital is a bad idea. There is nothing therapeutic about it. It's punishment and isolation," he said.

Dr Hickie said the practice could be ended immediately by hospital chief executives redirecting resources to mental health units.

"We need to create a safe environment where disturbances can be tolerated," Dr Hickie said, advocating for one-on-one skilled specialised nurse and medical practitioner care.

Dr Wright said he agreed the goal was ultimately to eliminate restrictive practices, but cautioned against over-simplifying the task.

"We are dealing with some of the most vulnerable individuals in the community and managing their needs in times of crisis is extremely challenging," he said.

"To simply declare a change in practice and implement it on that day runs the risk of creating a different kind of harm. It's frankly dangerous, in my opinion.

"We have to figure out why there are such wide variations between services," he said, adding that some mental health units were dealing with larger groups of more challenging patients.

Any strategy must focus on leadership for organisational change, drawing on data, developing the workforce, patient and carer involvement, prevention tools and debriefing to review all episodes of seclusion or restraint, Dr Wright said.

Mental health staff unfairly 'demonised'

Talk of seclusion often inadvertently demonised mental health services by casting them as outdated practices with recalcitrant staff, Dr Wright said.

"Our staff are really keen to eliminate the practice. They deal with patients on a 24/7 basis and keeping people safe is absolutely their guiding principle," Dr Wright said

"Being involved in a traumatic process affects everybody."

Dr Wright said he did not believe publicly disclosing this data was necessary to hold services to account, but if his review concluded otherwise he would make that recommendation. Victoria publishes its hospitals' seclusion and restraint data quarterly.

Mental Health Minister Tanya Davies said transparency in performance was important, pointing to the Health Ministry's annual report.

"To ensure enduring change, the use of clear methodology and evidence is needed to safely reduce the use of seclusion and restraint, and this must be examined through a comprehensive review," Ms Davies said in a statement.

Health Minister Brad Hazzard and Ms Davies have also requested the Legislative Council reopen its submissions for its inquiry into the management of health care delivery in NSW to allow mental health care to be addressed.

Opposition mental health spokeswoman Tania Mihailuk said the matter warranted its own inquiry.

"It's not enough to tack it onto the end of an inquiry that already has its terms of reference. Clearly the resourcing of mental health services across the state should have a standalong inquiry. We need accountability and transparency for patients, their families and staff," she said.