The prime minister is “extremely sick” and it is very likely he will need a ventilator, according to a medical expert.
Boris Johnson has spent the night in intensive care after his health deteriorated – 11 days after he initially tested positive for COVID-19.
Downing Street says Mr Johnson has been suffering from “persistent” coronavirus symptoms, and that he has been struggling to breathe.
Derek Hill, professor of medical imaging at University College London, said Mr Johnson could be given a breathing aid known as continuous positive airway pressure.
This bridges the gap between an oxygen mask and full ventilation, sending a blend of air and oxygen into the mouth at a steady rate.
However, Prof Hill warned many COVID-19 patients eventually “progress to invasive ventilation”, which is for people whose illness is so severe that they are struggling or unable to breathe for themselves.
A mechanical ventilator either does all the breathing for the patient or assists the patient’s own breathing, and they are normally placed under heavy sedation.
Prof Hill explained: “One of the features of COVID-19 in all countries seems to be that many more men become seriously ill than women – especially in the over 40 age group.
“Also, we know that people under about 60 seem to have a higher chance of making a recovery from critical illness with COVID-19 than older people.
“But there is no doubt this turn of events means Boris Johnson is extremely sick.”
Mr Johnson celebrated his 55th birthday last June.
Prof Hill added the prime minister’s situation highlights three key issues in the response to COVID-19.
“Firstly, many patients need help breathing, and there is a shortage of the mechanical ventilators that can do this – and in particular a shortage of the high-quality intensive care ventilators most suitable for COVID-19 patients who might need help breathing for more than a week,” he said.
“Secondly, COVID-19 patients need a huge amount of oxygen to help them breathe, which is potentially going to be in short supply.
“Thirdly, looking after people in intensive care requires skilled staff, and the experience of New York has been that finding enough skilled staff has been the greatest challenge.”
It is understood that Mr Johnson remained conscious when he was moved to intensive care, and that it was done as a precaution should be require ventilation.
The prime minister is likely to have undergone several tests – and it is possible that he will have blood and samples from his throat collected.
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According to the World Health Organisation, about 14% of COVID-19 patients will develop symptoms severe enough to need oxygen, and 5% will need intensive care treatment.
The latest figures show that the death rate of those admitted to intensive care in the UK now exceeds 50%.
Dr Simon Clarke, a microbiologist, told Sky News: “I’ll say this to you, the NHS, particularly at this moment, doesn’t give up intensive care beds just for people to be looked over – it doesn’t work like that, even for prime ministers.
“He would not be in intensive care unless he needed to be in intensive care, especially not at this time, and I think it’s probably about time that the press people in Number 10 started levelling with us about what his condition really is.”