A respiratory doctor at Belfast's Mater Hospital has warned that hospital oxygen supplies are under "extreme pressure".
Dr Nick Magee also said more younger patients were now being treated in hospital than during the first and second waves of the Covid-19 pandemic.
He said in the past they did not have to consult other NI hospitals about how much oxygen they had.
"That was never a thing in previous January flu problems," he told the BBC.
"But that is something we are now having to think of," he added.
Earlier this week Northern Ireland's Chief Medical Officer Dr Michael McBride said there is enough oxygen to cope with the current demand.
But according to Dr Magee the current level of oxygen being used in "bays" at the Mater means patients cannot charge their mobile phones by their bedside because of the "fire risk".
"It is all well controlled and we are making sure that we can share out that oxygen burden. That is something we are having to think about," he said.
"I can't say specifically about other regional hospitals but I know that they are under extreme pressure and it's just something we have to think of as a region.
"Can we supply oxygen adequately for the amounts of oxygen we are using in hospitals?"
The number of Covid positive hospital in-patients has increased significantly since last week - up from 599 a week ago to 850 on Thursday.
The number of people in ICU has also risen from 44 to 58 in the past week.
'They are scared'
Dr Magee said staff were concerned about having to cope with "large volumes" of patients requiring respiratory support.
He said the number of younger patients becoming increasingly sick with the virus was growing.
On Wednesday, the Mater Hospital moved six patients who had been on wards into ICU and also took patients from the Southern Health Trust.
"Recently I saw a 29-year-old patient, also three who were in their mid 30s that all required respiratory support on a ward," he told BBC News NI.
"They are frightened they are wearing specialist masks CPAP masks that help them breathe. They are scared."
The relentless pressure of the past 10 months and the prospect of a further surge in admissions over the next fortnight is weighing heavily on the minds of medics.
"We are really worried about next week," said Dr Magee.
"It's very busy this week, we are coping well but we are particularly concerned about next week.
"Normally, if we had somebody who needed a lot of respiratory support we would involve a high dependency unit but all the respiratory wards are becoming like high dependency units.
"Volume of sicker, younger patients is much greater and it's not something that I would [have] ever seen before," he added.
The Southern Health and Social Care Trust said its hospitals had limited infrastructure to manage high numbers of patients requiring oxygen so a regional agreement was in place to share resources across Trusts to support Covid-positive patients.
"As a result some patients have been diverted to Belfast or SE Trust to help reduce pressure on the Southern Trust hospital system," a statement said.
"Craigavon and Daisy Hill hospitals remain very busy with high numbers of Covid-19 positive patients who are dependent on oxygen therapy.
"These protocols are in place as part of regional surge planning to ensure that we can safely manage the current high volume of Covid-19 patients needing hospital care.
"Patients who are currently being treated in Craigavon and Daisy Hill have secure supplies of oxygen."