Ventilators have become prized in hospitals across the U.S. and beyond because they are desperately needed to treat very ill Covid-19 patients. But they are also feared for the damage they can inflict, and for the slim odds of survival they offer. Michelle Fay Cortez and Olivia Carville report that it's not yet clear what the long-term consequences ventilators have for those lucky enough to recover after having been on one.