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Cardiopulmonary resuscitation (CPR) is an emergency procedure that combines chest compressions often with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest. It is recommended in those who are unresponsive with no breathing or abnormal breathing, for example, agonal respirations.
CPR involves chest compressions for adults between 5 cm (2.0 in) and 6 cm (2.4 in) deep and at a rate of at least 100 to 120 per minute. The rescuer may also provide artificial ventilation by either exhaling air into the subject’s mouth or nose (mouth-to-mouth resuscitation) or using a device that pushes air into the subject’s lungs (mechanical ventilation). Current recommendations place emphasis on early and high-quality chest compressions over artificial ventilation; a simplified CPR method involving chest compressions only is recommended for untrained rescuers. In children, however, only doing compressions may result in worse outcomes. Chest compression to breathing ratios is set at 30 to 2 in adults.
CPR alone is unlikely to restart the heart. Its main purpose is to restore partial flow of oxygenated blood to the brain and heart. The objective is to delay tissue death and to extend the brief window of opportunity for a successful resuscitation without permanent brain damage. Administration of an electric shock to the subject’s heart, termed defibrillation, is usually needed in order to restore a viable or “perfusing” heart rhythm. Defibrillation is effective only for certain heart rhythms, namely ventricular fibrillation or pulseless ventricular tachycardia, rather than asystole or pulseless electrical activity. Early shock when appropriate is recommended. CPR may succeed in inducing a heart rhythm that may be shockable. In general, CPR is continued until the person has a return of spontaneous circulation (ROSC) or is declared dead.
CPR serves as the foundation of successful cardiopulmonary resuscitation, preserving the body for defibrillation and advanced life support. Even in the case of a “non-shockable” rhythm, such as pulseless electrical activity (PEA) where defibrillation is not indicated, effective CPR is no less important. Used alone, CPR will result in few complete recoveries, though the outcome without CPR is almost uniformly fatal.
Studies have shown that immediate CPR followed by defibrillation within 3–5 minutes of sudden VF cardiac arrest dramatically improves survival. In cities such as Seattle where CPR training is widespread and defibrillation by EMS personnel follows quickly, the survival rate is about 20 percent for all causes and as high as 57 percent if a witnessed “shockable” arrest. In cities such as New York, without those advantages, the survival rate is only 5 percent for witnessed shockable arrest.
In adults compression-only CPR by bystanders appears to be better than chest compressions with rescue breathing. Compression-only CPR may be less effective in children than in adults, as cardiac arrest in children is more likely to have a non-cardiac cause. In a 2010 prospective study of cardiac arrest in children (age 1–17) for arrests with a non-cardiac cause, provision by bystanders of conventional CPR with rescue breathing yielded a favorable neurological outcome at one month more often than did compression-only CPR (OR 5.54). For arrests with a cardiac cause in this cohort, there was no difference between the two techniques (OR 1.20). This is consistent with American Heart Association guidelines for parents.
When done by trained responders, 30 compressions interrupted by two breaths appears to have a slightly better result than continuous chest compressions with breaths being delivered while compressions are ongoing.
There is a higher proportion of patients who achieve spontaneous circulation (ROSC), where their heart starts beating on its own again, than ultimately survive to be discharged from hospital (see table above). This may be due to medical staff being ultimately unable to address the cause of the cardiac arrest, to other co-morbidities, or to the patient being gravely ill in more than one way. Ultimately, only 5–10% of patients in cardiac arrest will survive after an attempted resuscitation
While CPR is a last resort intervention, without which a person without a pulse will all but certainly die, the physical nature of how CPR is performed does lead to complications that may need to be rectified. Common complications due to CPR are rib fractures, sternal fractures, bleeding in the anterior mediastinum, heart contusion, hemopericardium, upper airway complications, damage to the abdominal viscera − lacerations of the liver and spleen, fat emboli, pulmonary complications − pneumothorax, hemothorax, lung contusions.
The most common injuries sustained from CPR are rib fractu