CHICAGO — One morning in March2021, at a nursing home in Evanston, resident Velta Saint registered an alarmingly low 44% oxygen level in her blood. Normal levels range from 95% to 100%, and one study recommends hospitalization for any patient with a reading below 90%. Medical workers tried to improve Saint’s respiration, then sent her to a hospital — which sent her back to the nursing home, before she was returned to the hospital, where she died. Saint’s ordeal came after her daughter, a registered nurse, said the home had been slow, in her opinion, to diagnose her condition and failed to trea...