Jelic was among the doctors treating COVID-19 patients in New York in the spring, when hundreds of people were turning up at the city’s hospitals everyday unable to breath. Patients were crammed into hallways; doctors were overworked. Normally, Jelic says, she might have seen eight or 10 patients in a day. In April, she and two fellows were responsible for 60, any of whom might crash and need to be intubated.

Lack of knowledge about the virus constrained what doctors did. Hospitals initially favored ventilation in part because doctors feared that high-flow therapy oxygen could aerosolize the virus and spread it to staff who didn’t have adequate supplies of personal protective equipment. (Now, of course, we know that the virus can be spread through aerosols generated from just normal talking and exhaling.) In some cases, aggressive intubation might have done more harm than good in patients who didn’t need it. Doctors stopped putting every patient on a ventilator once they realized the benefits of less invasive oxygen therapy and even turning patients onto their bellies, also known as proning.