Nearly all coronavirus patients who needed ventilators in New York's largest health system to help them breathe died, a study found. Overall, about 20% of Covid-19 patients treated at Northwell Health died, and 88% of those placed on ventilators died, according to the study. Just 12% of the patients in the study needed ventilators, Dr. Safiya Richardson at the Feinstein Institutes for Medical Research, Northwell Health, and colleagues found. The team looked at the electronic health records of 5,700 patients with coronavirus disease hospitalized at Northwell Health. “This study reported mortality rates only for patients with definite outcomes (discharge or death), and a longer-term study may find different mortality rates as different segments of the population are infected,” the Northwell Health team wrote.