What is the emergency procedure that helps to restore a person's breathing and heartbeat?

The emergency procedure designed to restore a person's breathing and heartbeat is cardiopulmonary resuscitation, commonly known as CPR. CPR is a lifesaving technique used in emergencies when someone's heart has stopped beating or they are not breathing. It involves a combination of chest compressions and rescue breaths, aimed at maintaining blood flow to vital organs until professional medical help can arrive.

This procedure is critical in cases of cardiac arrest as it helps to keep oxygenated blood circulating in the body, which can significantly increase the chances of survival and minimize brain damage. Other options do not address the immediate life-threatening situation of respiratory or cardiac failure. For instance, cardioversion is a procedure used to restore a normal heart rhythm and would not be initiated without the backup of CPR in an emergency. Cerebral thrombosis treatment focuses on blood clots in the brain, which is unrelated to heart and breathing issues. Cardiovascular rehabilitation is a program to help patients recover after heart events but is not an emergency procedure. Thus, the primary function of CPR as an immediate response makes it the correct answer.