Cardiopulmonary resuscitation (CPR) is a collection of interventions performed to provide oxygenation and circulation to the body during cardiac arrest. Our current, modern day approach to his process stemmed from the work of a handful of doctors in the 1950s and had now evolved into the process that we will discuss further here. The most widely accepted guidelines in North American are those produced by the American Heart Asociation (AHA). These are published every 5 years, after the International Liaison Committee on Resuscitation (ILCOR) meeting.`
Each year, almost 350,000 Americans die from heart disease. Half of these will die suddenly, outside of a hospital, because of the sudden cessation of spontaneous, organized cardiac function. The most common cause of sudden cardiac arrest in adults is ventricular fibrillation. Although advances in emergency cardiac care continue to improve the chances of survival, sudden cardiac arrest remains a leading cause of death in many parts of the world. As of 2016, cardiac disease continues to be the leading cause of death in the United States.
Seventy percent of cardiac arrests that occur outside of a hospital happen in the home. Other people never witness half of these cardiac arrests. Despite advances in emergency medical services, the survival rate remains low. Adult victims of non-traumatic cardiac arrest that receive resuscitation attempts by emergency medical services have a rate of survival to hospital discharge of only 10.8%. In comparison, adult patients who develop cardiac arrest in a hospital setting have rates of survival to hospital discharge of up to 25.5%.
The definitive treatment for ventricular fibrillation is electrical defibrillation. If a defibrillator is not readily available, brain death is likely to occur in less than 10 minutes. CPR is a means of providing artificial circulation and ventilation until defibrillation can be performed. Conventional manual CPR, combining chest compressions with rescue breathing, when done properly, can provide up to 33% of normal cardiac output and oxygenation.
The patient will be found unconscious and unresponsive with the absence of a pulse and spontaneous respirations. However, there is a prognostic benefit in determining the last time the patient was seen normal, or better yet, the time of loss of pulse. Additionally, collateral history from bystanders, family members, friends, and primary care physician can help etiologic evaluation.
There are no specific physical examination findings, but signs of cyanosis and reduced peripheral perfusion can suggest a cause for the arrest.
The absence of a palpable pulse indicates the need for Cardiopulmonary Resuscitation. Markers of lack of perfusion such as unresponsiveness, even with a doppler able carotid or femoral pulse, can still be an indication for CPR.
Note: The technique described here is intended for a healthcare provider performing one-rescuer CPR on an adult victim in the out-of-hospital setting. The modifications for children and infants, and for in-hospital CPR are listed below. These recommendations are current, as of the 2015 American Heart Association's Guidelines update for CPR and Emergency Cardiac Care.
The immediate recognition of cardiac arrest is essential, to both initiate the EMS response and to begin CPR as soon as possible. In this era of universal mobile phone availability, it is now possible to call 911 while remaining with the victim. CPR is now begun by first performing chest compressions (C), followed by opening the airway (A) and delivering rescue breaths (B) (the CAB sequence as compared to the former ABC sequence). The hands are placed on the lower half of the sternum, and chest compressions are begun at a rate of 100 to 120 compressions per minute. The goal is the depress the sternum to a depth of at least two inches while avoiding excessive depth of compressions. The chest wall should be allowed to recoil fully on the upstroke to maintain coronary artery perfusion pressure. Thirty compressions are performed, followed by a brief pause for two rescue breaths. Because of the critical contribution of chest compressions to coronary artery perfusion, interruptions in chest compressions should be minimized, and as short as possible when needed. 
After 30 chest compressions, the rescuer performs a head-tilt/chin lift maneuver to open the airway (assuming there is no suspicion of a cervical spinal injury). If a cervical spine injury is suspected, the airway is opened by using the jaw-thrust maneuver without extending the head. Two rescue breaths are administered: the rescuer takes a "regular" breath (not deep or excessive) and delivers a rescue breath lasting approximately one second, which should be enough just to allow the chest to rise. The process is repeated for a second rescue breath.
Ideally, a health care provider who is inclined to intervene as an out-of-hospital rescuer should have ready access to a barrier device such as a rescue mask. However, this is not always the case. Mouth-to-mouth rescue breaths have been the alternative, which many untrained rescuers are hesitant to perform, especially on an unknown victim. This is a decision that healthcare providers must make for themselves. Compression-only CPR has been accepted as appropriate for untrained lay rescuers. If extenuating circumstances prohibit a health care provider in the out-of-hospital setting from performing rescue breathing without a barrier device, it would be prudent to perform compression-only CPR until emergency management services (EMS) arrives.
The cycle of 30 chest compressions alternated with two rescue breaths is continued until an automated external defibrillator (AED) becomes available, or until additional help arrives.
By definition, infant CPR applies to patients whose age is less than one year. Child CPR applies to patients from one year of age through puberty. From puberty onward, adult CPR guidelines apply. The modifications for infant and child CPR are listed below. All other aspects of CPR follow the adult guidelines, including starting the process with the Compression first (CAB) sequence, and the rate of compressions being 100 to 120 per minute. The sternum should be depressed to a depth of approximately one-third of the anteroposterior diameter of the chest; this is about two inches in the child, and 1.5 inches in the infant.
Child CPR Modifications
Chest compressions on a child are performed by placing the heel of one or two hands (depending on the size of the child) over the lower half of the sternum. The chest is compressed to a depth of approximately two inches, at a rate of 100 to120 per minute. After 30 compressions, administer two sequential breaths and return to chest compressions. Continue the cycle of 30 compressions to two breaths until help arrives.
Chest compressions on an infant are performed by placing two fingers on the sternum just below the nipple line. The infant's chest is compressed to a depth of approximately 1.5 inches, at a rate of 100 to 120 per minute. After 30 compressions, administer two sequential breaths and return to chest compressions. Continue the cycle of 30 compressions to two breaths until help arrives.
In the hospital setting, ventilation is usually performed with a bag-valve-mask (BVM) device. Bag-valve-mask ventilation needs to be performed by a provider skilled in its use. If the patient is not intubated, CPR is done by one provider performing chest compressions, while the second provider provides BVM ventilation. The ratio of compressions to ventilations changing to 15 compressions to two ventilations. Once a patient is intubated, it is no longer necessary to perform "cycles" of compressions and ventilation. Chest compression is performed continuously, while rescue breaths are given independently via the BVM at a rate of 10 per minute (one ventilation every six seconds). Unskilled operators frequently tend to provide BVM at a higher frequency than this.
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