For most people—about 80%, according to the World Health Organization—COVID-19 won't result in serious illness. But that still means 1 in 5 people who contract the infection will end up with a more severe form of the disease, and will need hospitalization. In the most severe cases—typically in those with underlying conditions like high blood pressure, heart and lung problems, or diabetes—COVID-19 patients may be admitted to a hospital's intensive care unit (ICU), where they can benefit from respiratory support through a ventilator.

According to multiple studies, the majority of patients admitted to the ICU and require ventilation do not survive. Data from the Intensive Care National Audit and Research Center in London shows that, of outcome data available for 690 ICU patients, 346 (or 50.1%) patients died, while 344 (49.9%) were discharged alive. Similar findings were shown in an Italian study published in JAMA: Of 1,581 patients with available ICU disposition data at the end of the study, 920 patients were still in the ICU—but of the remaining 661 patients, 405 (61.3%) died while 256 (38.7%) were discharged.

Of course, being discharged from the ICU is the best-case scenario—but sometimes, even after coming off of respiratory support, hospitalized patients can experience another issue: ICU delirium.