A senior figure at Wales' largest hospital says staff are in uncharted territory as it prepares to face "a huge wave" of coronavirus cases.
So far 14 patients have been admitted to intensive care at the University Hospital of Wales, Cardiff with the virus.
But Dr Richard Skone said efforts by staff so far had been monumental.
More than 800 clinicians from across different departments have been given specialist Covid-19 training.
Dealing with the virus is set to dominate the hospital's workload in coming weeks and months.
"We've modelled for several different scenarios, the tension comes from not knowing which one we'll be on," said Dr Skone, clinical board director for specialist services.
"It's quite difficult to know without landing in the middle of a situation what to expect - we've never been here before - but we certainly think we're prepared as well as we can."
Everyone is working at their maximum, they're quite stressed but with that comes a lot of good work and good will from everybody in the hospital.
"We've made every arrangement we can to maximise what we can do and have expanded our intensive care capacities quite a lot more than we had thought possible."
The extra bed capacity to be provided at a new field hospital, with up to 2,000 beds, at the Principality Stadium would "play a vital role", he said.
Dr Skone said it was not just about the numbers of beds but also in keeping the flow of patients going.
"As you can imagine, everybody passes through different stages of coronavirus at different times and each person is going to need to be in the right place at the right time - that flow is going to be important to keeping beds open," he added.
"What we're expecting with covid virus is essentially a huge wave of people coming up to hospital."
But he said government measures on restricting contact would hopefully bring the peak in the wave of cases down - and widening it would improve the NHS's chances of being able to cope.
Dr Skone expects the peak of the epidemic to be towards the end of May to the beginning of June but that could change depending on how people adhere to the "stay at home" guidance.
"We're hoping by the end of this week we'll have a better idea of the trajectory we're on."
"The feeling at the moment is obviously everyone is working at their maximum, they're quite stressed but with that comes a lot of good work and good will from everybody in the hospital."
"There's a lot of anxiety certainly about what we might be facing but what's come over most is how people are willing to come together."
'They're very sick patients, but we've had some successes'
Dr Chris Hingston, intensive care consultant
"It's busy - we've had quite a few referrals in the last hour actually.
"It's a difficult environment to work in - the covid area as we're calling it - with the coronavirus in personal protective equipment (PPE).
"But people are working hard, working together and I guess getting used to working in that environment."
He expects to see case numbers increase "heavily" and exponentially - what had been three a day has already grown to five referrals over the last couple of hours.
"It goes without saying, they're very sick patients, but we've had some successes. We've taken people off breathing machines on three occasions now - off the ventilators - so that provides, you know, a real lift in the day when that happens."
"There are people getting better from this disease which is encouraging. But some people take longer than others to get better and of course, sadly, some people - as the public know - aren't surviving this illness."
He said staff were approaching work with a degree of apprehension but staff were drilled in using PPE and felt prepared for a "huge uplift and surge capacity" in intensive care.
"There may come a time, with the predictions where we can't cope with that," Dr Hingston added.
"But we'll manage for hopefully quite a while yet and hopefully with the social distancing that people are practising will manage to avoid that - that remains to be seen."
He said the unit could handle at least 120 beds.
"We've got ventilators, we've got space - the big factor will be getting enough nursing staff to manage those patients; we usually work on a one-to-one basis. We're really comfortable that we'll have to move away from that within national guidelines, maybe up to one-to-three to four.
"But there will be a limit on what we can provide in terms of goodness in care, so that we can actually get these patients better. Perhaps going beyond that, we may not see the usual benefits of critical care that we would hope for."
Asked about his message to the public, Dr Hingston said: "The chances are very much on your side.
"Most people will get this disease and not be affected by it; even those who come into hospital will just get better and go home. Of course there is the, you know, smaller percentage of people who need our help. And we will do our utmost to deliver the best possible care that we can to get you better and back home to your families."
He said they appreciated the difficulties for families not being able to be at the bedsides of patients.
"But they need to know that we are looking after your loved ones - there is someone with them and we are caring for them and we are doing our utmost to get them better, and get them home to you," he said.
Training for the virus - 'all hands on deck'
Staff are currently being trained in a simulation ward, using actors and mannequins, so they can practice their decision-making - and also learn how to treat people safely.
Prof Ben Hope-Gill, respiratory physician and assistant medical director, is responsible for training and he said it was about staff feeling confident and refreshing skills.
"Because of the number of patients that we're expecting to see... it's going to be a case of all hands on deck," he said.
"A lot of clinicians who are working in very different parts of the hospital are going to have to get involved in caring for patients with respiratory illness."
"We've been able to train 250 last week, another 250 this week and by the end of next week more than 800 staff will have been through this very tailored simulation training programme, covering a range of scenarios that they expect to meet."
"I'm very mindful that we're going to be looking after a lot of patients who are sick. And I'm also very mindful that that they are loved ones, and they are members of families, and that it's going to be a very, very difficult time, both for the patients, and for their families.
"And that's very sobering, actually."