Masha says that Yao saved her life after she was shot by an unknown assailant and points to a long scar down the center of her chest. Yao is an EMT, not a cardiac surgeon, and it is highly unlikely that he would possess the skills and equipment to do a sternotomy. Even if he did perform direct cardiac massage, it would be quicker to do a limited left lateral thoracotomy and access the heart from between the ribs.
In the opening scene, Melissa McCarthy's aviator sunglasses reflect a chase car and camera crew, alternating between locations and various fabricated backgrounds.