"If the bloodied man at Hennepin had arrived a day earlier, he might have died while his doctors continued to monitor him. But he had stumbled into an experiment. A small group of Hennepin doctors had decided to place an ultrasound machine in the E.R.’s trauma bay, to see if they could quickly diagnose hemorrhaging in the heart."

https://www.newyorker.com/science/annals-of-medicine/could-ultrasound-replace-the-stethoscope