Collecting that money would have given Centinela a measure of relief. But the bills went unpaid, and the century-old medical center was sold. The new owners slashed services, closed half the operating rooms and laid off a third of the employees. Who owed Centinela that elusive $25 million? According to hospital officials, it was health insurance companies. “Insurers have found a very creative way of denying, delaying or slowing payments in a way that is having a real impact on patient care and some of our survival,” said Von Crockett, Centinela’s chief executive. “Every single doctor and hospital is writing off money they are legally owed but don’t collect. It’s an insane situation.”