Paramedics angry over rising expectations and sluggish pay are threatening to let their registrations lapse, making it illegal for them to work.
The novel industrial action comes as Health Minister Ryan Park on Wednesday unveils a trial embedding cardiac bypass machines in ambulances.
The Health Services Union says 1500 paramedics - nearly one-in-three in NSW Ambulance ranks - have pledged to boycott professional registration which is due for renewal by December 1.
"The skills and value of paramedics has skyrocketed over the past decade as they have taken on increasingly clinical and public health functions," the union said on Wednesday.
"However, the pay of NSW paramedics does not reflect this uplift in skills and they have fallen well behind similar health professionals in NSW due to the 12-year-long wage cap that prevented meaningful wage bargaining."
Under the previous coalition government, wage rises were capped, throttling unions' ability to negotiate on pay.
While Labor has scrapped that cap, its offer of a four per cent wage rise to all public sector workers is unpalatable to paramedics aligned to both the HSU and rival union, the Australian Paramedics Association.
The pay headache comes as the health minister launches a new innovative clinical trial to make a cardiac bypass machine mobile.
While a trial was conducted in Victoria earlier this year, NSW says the staffing model in its trial is a world-first.
Critical care paramedics would work alongside specialist pre-hospital critical care doctors in a dedicated vehicle to treat cardiac arrest patients.
Mobilising ECMO has the potential to increase the survival rate of some patients in cardiac arrest from less than five per cent to around 30 per cent.
"In instances of cardiac arrest – time is particularly of the essence," Mr Park said.
"This world-leading initiative can save time to treatment and has the potential to save lives."
Westmead Hospital, Royal Prince Alfred Hospital and St Vincent's Hospital in Sydney are participating in the trial by receiving patients who have been put on ECMO by NSW Ambulance.