Paramedics were called in to work on the patient, believed to be a male, in cardiac arrest early Sunday morning.

The Star has been told a retrieval team was en route from Tamworth - more than two hours after the patient had presented - when the person was declared dead.

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The hospital had no doctor from Thursday to Monday; the usual medical officer was on leave and Hunter New England Health (HNEH) couldn't find a locum.

NSW Nurses and Midwives Association general secretary Brett Holmes said two nurses had been on duty in an unfamiliar, new emergency department; the union has been calling for a minimum of three staff.

NSW Ambulance's CERS Assist protocol - the Clinical Emergency Response Assistance Initiative - was put in place, sources said.

According to a NSW Ambulance document, this means paramedics providing "urgent additional clinical assistance in response to a rapidly deteriorating patient in a public health care facility ... if a facility is unable to provide sufficient clinical resources to manage [them]."

HNEH was unable to respond to specific questions about the incident before deadline.

"Tenterfield Hospital has highly skilled nursing staff who are qualified to manage emergency presentations and were supported by emergency department staff at Tamworth and Armidale hospitals ... a locum medical officer is now providing coverage", a spokesperson said.

Mr Holmes said it was "a terrible tragedy".

"We don't know whether it would have changed the outcome, but it would have made it a much easier situation to manage with another pair of skilled hands."

The nurses had received telehealth help from a Narrabri doctor, but technology "can't replace the physical presence of a medical officer or additional skilled nurses".

"We don't know whether it would have changed the outcome, but it would have made it a much easier situation to manage with another pair of skilled hands," Mr Holmes said.

He said it had been "very tough" on staff - and was compounded by having to deal with a bus crash the next day in which almost 20 students were hurt.

"It is no wonder that our members are on edge and that the community is on edge."

NSW Health Services Union secretary Gerard Hayes said the incident was "yet more evidence of highly skilled paramedics being underpaid for the work they do".

"Our paramedic workforce is highly trained and capable of dealing with very complex medical situations, but their pay does not reflect this level of responsibility," he said.

"The situation also reflects the deep and unfortunate inequity between metropolitan and regional health."