Covid: What happens in a hospital intensive care unit?
Intensive care units are specialist wards within a hospital that look after people who are very ill.
There are around 5,000 permanent intensive care beds in the UK.
Each one is equipped with a lot of highly technical monitoring equipment and staff who've been specially trained.
Coronavirus patients have problems with their lungs and so are usually admitted so they can get help breathing.
Here BBC health correspondent Laura Foster explains how they work and what it means for Covid-19 patients.
Video by Tobias Chapple, Terry Saunders and Laura Foster.