Step-by-step explanation:
The paramedics after arriving were surprised to see Greg performing chest compression on Tony's chest because Tony was still able to breathe though he was shallow breathing. Chest compression is given to person suffering by cardiac arrest. By giving chest compression, oxygenated blood circulate through the body and keeps the other organs and specially the brain alive for some time until defibrillator is given. Chest compression provides adequate blood flow in the body.