Hanson

The first time cardiologist Sonia Tolani performed CPR outside a hospital was in 2009.

She was on the subway in New York City, headed home from work, when she saw a man slump to the ground and stop breathing.

"It was super crowded, it was like rush hour," she remembers. "I just decided we needed to do something, and dragged him out into the center of the subway train [and] I just started doing CPR."