The brutal flu season was partly to blame for the record 720,564 presentations at the state's emergency departments between July and September, a 9.4 per cent increase (up by 62,000 presentations) on the same quarter last year, according the the latest Bureau of Health Information (BHI) report.

The staggering volume - the most NSW EDs have ever seen - was almost equivalent to one presentation for every 10 people living in NSW, though many patients accounted for multiple presentations.

Roughly 30 per cent of patients in emergency departments did not have their treatment start on time, a 3.6 percentage point increase on the winter quarter of 2016, showed the report released Wednesday.

Just under one-third of patients (31.6 per cent) spent more than four hours in ED, up 3.3 percentage points on last year, and falling significantly short of the Premier's priority target of getting 81 per cent of patients out of EDs within the four-hour window.

Among ED patients admitted to hospital, roughly one in three left the ED within four hours.

The fall in performance measures of three to four percentage points paled in comparison to the huge rise in the number of patients presenting to emergency departments and arriving by ambulance (in the order of nine to 10 per cent).

The results suggested many hospitals were remarkably resilient in the face of immense pressure, BHI acting chief executive Dr Kim Sutherland said.

NSW Health Deputy Secretary System Purchasing and Performance Suzanne Pearce said NSW was the best performing state in the country for access to emergency care and elective surgery amid the winter surge.

"We have experienced record numbers of presentations to our hospital emergency departments, with more than 320 patients arriving for treatment every hour of every day for those three months," Ms Pearce said, congratulating hospital and ambulance staff.

Yet treatment and wait times suffered significantly across dozens of the state's emergency departments, most notably at two hospitals in south-west Sydney.

Fairfield Hospital was deluged by patients arriving by ambulance, up 49.5 per cent on the same quarter last year, and had to contend with a 11.5 per cent increase in ED presentations, including a staggering 82.4 per cent rise in T1 cases - the most critical patients with life-threatening conditions.

Over 40 per cent of patients at Fairfield's ED were not treated on time, a 14.7 percentage point rise on the same quarter last year, and almost 45 per cent of patients were in the ED for over four hours, a 21.5 percentage point rise.

Dr Sutherland said the marked rise in ambulance arrivals and T1 patients at Fairfield, though small in number, suggested the hospital was grappling with an increase in the sickest, most resource-intensive patients.

The hospital was able to maintain its elective surgery performance, with 99.7 per cent performed within clinically recommended time frames, suggesting the influx in the ED did not have a detrimental flow-on effect, Dr Sutherland said.

At Bankstown Hospital, almost 47 per cent of patients did not start treatment on time, a 14.6 percentage point rise on winter 2016, and more than 40 per cent of patients were still in the ED four hours after arriving, a 12.4 percentage point increase.

Westmead and Blacktown hospitals managed to buck the trend by recording improvements in performance. Most notably Blacktown was the only hospital in the state to improve its four-hour performance by more than five percentage points in spite of the massive increase in activity.

The Australasian College of Emergency Medicine (ACEM) said patient lives were being put at risk because the rise in activity was not being matched by an increase in staff levels and resourcing.

"The fact that the data looks this good under enormous pressure is a testament to the tenacity of the doctors, the nurses, the orderlies, and all hospital staff, but it's a finite resource," ACEM NSW faculty chair Dr Chris Trethewy

Overcrowding in emergency departments hampered efforts to rapidly identify patients in greatest need of emergency care, Dr Trethewy said.

"Without adequately addressing the underlying problems of access block, overcrowding and acute care bed shortages across NSW, we will not fix the current situation and patients will remain at risk.

"We need to consider all the vulnerabilities at every point that contribute to a patient's journey across the network," he said.

AMA NSW president Dr Brad Frankum said there was no doubt the horrendous flu season was to blame for some of increase. Health authorities recorded 103,193 confirmed flu cases from January to November 2017, almost triple the 2016 total of 35,537.

"But influenza does not fully explain the staggering numbers of ED presentations," Dr Frankum said.

"With every BHI report we have seen successive years and quarters of increasing activity."

The previous summer, autumn and spring months were all "horror quarters" for EDs.

"Demand is beyond capacity and it is still growing ??? this pressure is continuous, unrelenting and building."

"It is entirely obvious we cannot continue like this."

Dr Frankum suspected a lack of access to after-hours GPs may have contributed to the increase in less urgent ED presentations.

"The pressure on EDs absolutely reflects back on the availability of general practice," he said.

"We need greater capacity at hospitals, we need to better utilise general practice and other out-of-hospital specialist care, and we need to do it fast."

"A lack of fat in the system" was the likely problem in SWSLHD, Dr Frankum said.

"When you are always at capacity, and even on relatively quiet days your performance is struggling to keep up, then you are of course going to be more fragile with an unexpected rise in activity," he said.

Fairfield, in particular had one of the most multicultural populations in the country, with a high proportion of Syrian refugees, many of whom had lower level of health literacy and were more likely to have long-term health problems than the general population.

"Hospitals in south-west Sydney weren't only dealing with influenza, they were dealing with influenza in patients who had heart failure and diabetes," he said.

Ms Pearce said NSW Health was already preparing for next year's flu season and had sought advice from the federal department of health on the progress towards adding more protective vaccines to the National Immunisation Program for the elderly in 2018.

A spokesperson for SWSLHD said both Bankstown-Lidcombe and Fairfield Hospitals were adjusting the new demand levels to ensure patients were seen quicker and the LHD was working on ways to improve ED performance during the winter surge period, including implementing the Emergency Treatment Performance Transformation Program.