Circulation

CPR (or cardiopulmonary resuscitation) is a combination of rescue breathing (mouth-to-mouth resuscitation) and chest compressions. If someone isn't breathing or circulating blood adequately, CPR can restore circulation of oxygen-rich blood to the brain and heart. Without CPR irreversible brain damage can occur in 3-4 minutes and the chance of survival from cardiac arrest reduces by 10% per minute without defibrillation. 

CPR may be necessary during many different emergencies, including accidents, near-drowning, suffocation, poisoning, smoke inhalation, electrocution injuries, and suspected sudden infant death syndrome (SIDS) 

Reading about CPR and learning when it's needed will give you a basic understanding of the concept and procedure, but it's strongly recommended that you learn the details of how to perform CPR by taking a course. If CPR is needed, using the correct technique will give someone the best chance of recovery. 

CPR is most successful when started as quickly as possible, but you must first determine if it's necessary. It should only be performed when a person shows no sign of life or agonal breathing.

First, determine that it's safe to approach the person in trouble. For instance, if someone was injured in an accident on a busy highway, you'd have to be extremely careful about ongoing traffic as you try to help. Or if someone touched an exposed wire and was electrocuted, you'd have to be certain that he or she is no longer in contact with electricity before offering assistance to prevent becoming electrocuted yourself. (For instance, turn off the source of electricity, such as a light switch or a circuit breaker.) 

Once you know that you can safely approach someone who needs help, quickly evaluate whether the person is responsive. Look for things such as eye opening, sounds from the mouth, or other signs of life like movement of the arms and legs. A shake and shout can help determine if there is any level of responsiveness. This can be done by gently shaking the shoulders and asking if they're all right.

If there is a response leave them in position if safe then gain assistance. If there is no response shout for help. The next step is to check if the victim is breathing. You can determine this by LOOKING at the persons chest for the rise and fall of breaths and LISTENING for the sound of air going in and out of the mouth or nose and FEELING for air from the patients mouth against your face.  In a CPR or basic life support (BLS) course, participants practice techniques for determining if breathing or circulation is adequate. If you can't determine whether someone is breathing or has agonal breathing, you should call for a defibrillator and/or 999 and then begin CPR and continue until help arrives.

Whenever CPR is needed, remember to call for emergency medical assistance. Current CPR courses teach you that if you are alone with an unresponsive infant or child, give CPR for 1 minute before leaving the victim to obtain emergency assistance.