NSW patients heading to emergency departments during the pandemic were generally happy with thecare they received but one in five say their medical advice didn't add up.

The Bureau of Health Information surveyed almost 21,000 patients admitted to 77 large emergency departments across urban and rural NSW from mid-2020, at the height to the pandemic, to mid-2021.

It found 90 per cent of patients said the care given to them by doctors and ED staff was good or very good but about 20 per cent said they received "contradictory" information about their condition or treatment.

"There did not appear to be one person responsible overall for my care," one patient said.

Another patient who waited for treatment as COVID-19 cases ravaged the state said "no one attended to me".

"I waited a long time for treatment and to see a doctor ... I was exhausted and sat on the chair all night."

But even though wait times were high and staff were stretched, the care given was professional.

Almost 80 per cent of patients said ED staff checked on their condition while they were waiting to be treated, up from 75 per cent the previous year.

"For most questions, there was no significant difference in experiences between patients in large rural and urban EDs, including for overall ratings of care, ratings of health professionals and outcomes of care," BHI chief executive Diane Watson said on Wednesday.

NSW Nurses and Midwives' Association general secretary Brett Holmes said stretched ED staff couldn't provide patients with all the information needed while they waited for treatment.

The union is calling for one to three nurse to patient ratios, pointing to Westmead, Wollongong and Wyong hospitals, which performed worse than the NSW median.

"We've indicated to the government numerous times how tough conditions have become inside many emergency departments due to chronic understaffing issues," Mr Holmes said.

"Short-staffing was impacting on patient care and safety well before the pandemic and these results show how it was exacerbated during COVID-19 peaks."

A BHI quarterly report released last month revealed 763,257 people turned up at NSW public hospitals in late 2021 needing emergency care.