The Intensive Care National Audit and Research Centre (ICNARC) analysed the outcomes for 165 people confirmed to have the virus treated across 285 critical care units in England, Wales and Northern Ireland since February 29.
The data, from an audit of 775 people who have been or are in critical care for Covid-19, found 79 died, while 86 survived. The remaining 610 are still in intensive care.
It comes as the Government has drafted in the military to build NHS Nightingale, a 4,000-capacity field hospital at the ExCel Centre in London’s Docklands, due to open next week.
Three others are also planned in Birmingham, Manchester, Cardiff and Scotland.
Health officials are scrambling to increase critical care beds, with an NHS England boss warning in a conference call on Tuesday that London would run out in four days without urgent measures.
London North West University Healthcare NHS Trust, the worst affected in the country, has seen 21 fatalities since Friday among patients diagnosed with coronavirus.
One doctor told The Observer: “The truth is that quite a lot of these individuals [in critical care] are going to die anyway and there is a fear that we are just ventilating them for the sake of it, for the sake of doing something for them, even though it won’t be effective. That’s a worry."
The report also found that nine of the 79 who died in critical care this month were between 16 and 49, with this age group accounting for 28 of the 86 who survived.
While most were aged over 70, it brings into question earlier claims that the young were much less likely to become infected.
The analysis also put men most at risk - seven in ten critical care patients were male - and over 70 per cent were overweight, obese or clinically obese.
Meanwhile there are growing calls for the Government to extend its roll out of tests for frontline NHS workers to those without symptoms.
Currently medics are only covered if they have been self-isolating, but some doctors and nurses fear that asymptomatic carriers are spreading the virus on wards, and point to widespread precautionary staff shortages as a need for certainty.