It’s 3 a.m. Your child is struggling to breathe. You rush her to the nearest emergency room. The waiting room is packed. And there is only one emergency physician responsible for a room full of sick and frightened patients. You might assume the hospital couldn’t find another doctor to work that night. But what if someone decided another doctor costs too much?

Most patients assume the doctors working in an emergency room work for the hospital whose name is on the building. Often, they don’t. Hospitals frequently contract with outside companies to staff emergency departments with emergency physicians. Increasingly, those companies are owned by private-equity firms, whose business model depends on generating returns for investors, creating an environment where clinical staffing is an expense line item to be managed, rather than a critical safeguard for patients.