With 116 COVID-19 patients in NSW currently in intensive care, almost 80 per cent of the state's existing intensive care bed capacity in hospitals is already filled. This includes both COVID-19 patients and other patients.

There are 698 COVID-19 patients hospitalised in NSW in total.

At least two western Sydney hospitals - Westmead and Blacktown - have called "code yellow" emergencies in recent days as patient numbers climb.

Western Sydney Local Health District said in a statement on Thursday it was caring for more than 1500 COVID-19 patients in the community. As of Wednesday, there were 121 COVID-19 patients in Westmead Hospital and 15 at Blacktown.

Some critical patients have been transferred to other hospitals to lighten the load.

Westmead has also opened a makeshift "short stay unit" in the emergency department to help ease "ramping" delays in offloading COVID-19 patients from ambulances, which have stretched beyond six hours.

NSW Health says it currently manages about 500 intensive care beds across NSW hospitals, with a surge capacity of about 2000 when required. The government has reiterated the hospital system can cope with increasing patient numbers.

There are about 2000 ventilators available, one for each bed.

But NSW Nurses and Midwives' Association secretary Brett Holmes said that a 2000-bed ICU surge capacity does not equate to ideal care for 2000 ICU patients.

While the government had sought since the pandemic began to train intensive care nurses, Mr Holmes said the system likely could not maintain 2000 intensive care beds without diluting nursing care or resources.

"Their probable intention to staff them is by using a different ratio of staff to patients than would currently be standard," Mr Holmes told AAP.

"(They'd be) using less experienced staff at the bedside and then having a supervisor, an experienced intensive care nurse, to oversee the work of four others.

"We already had a shortage of intensive care nurses before this outbreak, people were doing lots of overtime, there weren't the ratios we believe are appropriate."

Mr Holmes also said that while NSW Health's surge capacity may involve the transformation of general wards, recovery rooms and operating theatres into intensive care wards, these may not have negative room pressure.

This could increase the risk of COVID-19 leaks to hospital staff. Some 1200 NSW healthcare staff are already in isolation due to COVID-19 exposure.

Australian Medical Association president Omar Khorshid told ABC Radio National on Thursday that Australia's hospitals are "usually full all the time" and the cessation of elective surgeries in NSW would help free up intensive care beds.

But he said resourcing constraints would only tighten as case numbers climb - meaning NSW had to continue trying to suppress COVID-19 infections.

"We don't have staff just on tap," Dr Khorshid said.

"At the end of the day, you're going to reach a point where your already-trained staff are no longer available, and you have to go then to the next level. People who don't normally do those sorts of jobs, (you) have to retrain them.

"At the end of the day, you don't want an orthopaedic surgeon like me running an ICU bed, that's not ideal, but it's something you do in a crisis."

Australian Associated Press