Cardiopulmonary resuscitation (CPR) is an emergency medical procedure for a victim of cardiac arrest or, in some circumstances, respiratory arrest. CPR is performed in hospitals, or in the community by laypersons or by emergency response professionals.
For 50 years CPR has consisted of the combination of artificial blood circulation with artificial respiration i.e., chest compressions and lung ventilation. However, in March 2008 the American Heart Association and the European Resuscitation Council, in a historic reversal, endorsed the effectiveness of chest compressions alone--without artificial respiration--for adult victims who collapse suddenly in cardiac arrest (see Cardiocerebral Resuscitation below). CPR is generally continued, usually in the presence of advanced life support, until the patient regains a heart beat (called "return of spontaneous circulation" or "ROSC") or is declared dead.
CPR is unlikely to restart the heart, but rather its purpose is to maintain a flow of oxygenated blood to the brain and the heart, thereby delaying tissue death and extending the brief window of opportunity for a successful resuscitation without permanent brain damage. Defibrillation and advanced life support are usually needed to restart the heart.
CPR has been known in theory, if not practice, for many hundreds or even thousands of years; some claim it is described in the Bible, discerning a superficial similarity to CPR in a passage from the Books of Kings (II 4:34), wherein the Hebrew prophet Elisha warms a dead boy's body and "places his mouth over his". In the 19th century, Doctor H. R. Silvester described a method (The Silvester Method) of artificial respiration in which the patient is laid on their back, and their arms are raised above their head to aid inhalation and then pressed against their chest to aid exhalation. The procedure is repeated sixteen times per minute. This type of artificial respiration is occasionally seen in films made in the early part of the 20th century.
A second technique, called the Holger Neilson technique, described in the first edition of the Boy Scout Handbook in the United States in 1911, described a form of artificial respiration where the person was laid on their front, with their head to the side, and a process of lifting their arms and pressing on their back was utilized, essentially the Silvester Method with the patient flipped over. This form is seen well into the 1950s (it is used in an episode of Lassie during the Jeff Miller era), and was often used, sometimes for comedic effect, in theatrical cartoons of the time (see Tom and Jerry's "The Cat and the Mermouse"). This method would continue to be shown, for historical purposes, side-by-side with modern CPR in the Boy Scout Handbook until its ninth edition in 1979.
However it was not until the middle of the 20th century that the wider medical community started to recognize and promote artificial respiration combined with chest compressions as a key part of resuscitation following cardiac arrest. The combination was first seen in a 1962 training video called "The Pulse of Life" created by James Jude, Guy Knickerbocker and Peter Safar. Jude and Knickerbocker, along with William Kouwenhouen had recently discovered the method of external chest compressions, whereas Safar had worked with James Elam to prove the effectiveness of artificial respiration. It was at Johns Hopkins University where the technique of CPR was originally developed. The first effort at testing the technique was performed on a dog. Soon afterwards, the techique was used to save the life of a child. Their combined findings were presented at annual Maryland Medical Society meeting on September 16, 1960 in Ocean City, and gained rapid and widespread acceptance over the following decade, helped by the video and speaking tour they undertook. Peter Safar wrote the book ABC of resuscitation in 1957. In the U.S., it was first promoted as a technique for the public to learn in the 1970s.
Mouth-to-mouth ventilation was combined with chest compressions based on the assumption that active ventilation is necessary to keep circulating blood oxygenated, and the combination was accepted without comparing its effectiveness with chest compressions alone. However, research over the past decade has shown that assumption to be in error, resulting in the AHA's acknowledgment of the effectiveness of chest compressions alone (see Cardiocerebral resuscitation below).
The medical term for the condition in which a person's heart has stopped is cardiac arrest (also referred to as cardiorespiratory arrest). CPR is used on patients in cardiac arrest in order to oxygenate the blood and maintain a cardiac output to keep vital organs alive.
Blood circulation and oxygenation are absolute requirements in transporting oxygen to the tissues. The brain may sustain damage after blood flow has been stopped for about four minutes and irreversible damage after about seven minutes. If blood flow ceases for 1 or 2 hours, the cells of the body die unless they get an adequately gradual bloodflow, (provided by cooling and gradual warming, rarely, in nature [such as in a cold stream of water] or by an advanced medical team). Because of that CPR is generally only effective if performed within 7 minutes of the stoppage of blood flow. The heart also rapidly loses the ability to maintain a normal rhythm. Low body temperatures as sometimes seen in drowning prolong the time the brain survives. Following cardiac arrest, effective CPR enables enough oxygen to reach the brain to delay brain death, and allows the heart to remain responsive to defibrillation attempts.
If the patient still has a pulse, but is not breathing, this is called respiratory arrest and artificial respiration is more appropriate. However, since people often have difficulty detecting a pulse, CPR may be used in both cases, especially when taught as first aid (see below).
Research has shown that lay personnel cannot accurately detect a pulse in about 40% of cases and cannot accurately discern the absence of pulse in about 10%. The pulse check step has been removed from the CPR procedure completely for lay persons and de-emphasized for healthcare professionals.
In March 2007, a Japanese study in the medical journal The Lancet presented strong evidence that compressing the chest, not mouth-to-mouth (MTM) ventilation, is the key to helping someone recover from cardiac arrest. An editorial by Gordon Ewy MD (a proponent of CCR) in the same issue of The Lancet called for an interim revision of the ILCOR Guidelines based on the results of the Japanese study, but the next scheduled revision of the Guidelines was not until 2010. However, on March 30, 2008, the American Heart Association broke away from the ILCOR position and stated that compression-only CPR works as well as, and sometimes better than, traditional CPR.
The method of delivering chest compressions remains the same, as does the rate (100 per minute), but the rescuer delivers only the compression element which, the University of Arizona claims, keeps the bloodflow moving without the interruption caused by MTM respiration. It has been claimed that the use of compression only delivery increases the chances of lay person delivering CPR.
Rhythmic abdominal compression-CPR works by forcing blood from the blood vessels around the abdominal organs, an area known to contain about 25 percent of the body's total blood volume. This blood is then redirected to other sites, including the circulation around the heart. Findings published in the September 2007 issue of the American Journal of Emergency Medicine using pigs found that 60 percent more blood was pumped to the heart using rhythmic abdominal compression-CPR than with standard chest compression-CPR, using the same amount of effort. There was no evidence that rhythmic abdominal compressions damaged the abdominal organs and the risk of rib fracture was avoided. Avoiding mouth-to-mouth breathing and chest compressions eliminates the risk of rib fractures and transfer of infection.
However, “cough CPR” cannot be used outside the hospital because the first symptom of cardiac arrest is unconsciousness in which case coughing is impossible. Further, the vast majority of people suffering chest pain from a heart attack will not be in cardiac arrest and CPR is not needed. In these cases attempting “cough CPR” will increase the workload on the heart and may be harmful. When coughing is used on trained and monitored patients in hospitals, it has only been shown to be effective for 90 seconds.
The American Heart Association (AHA) and other resuscitation bodies do not endorse "Cough CPR", which it terms a misnomer as it is not a form of resuscitation. The AHA does recognize a limited legitimate use of the coughing technique:
"This coughing technique to maintain blood flow during brief arrhythmias has been useful in the hospital, particularly during cardiac catheterization. In such cases the patients ECG is monitored continuously, and a physician is present.
There is a clear correlation between age and the chance of CPR being commenced, with younger people being far more likely to have CPR attempted on them prior to the arrival of emergency medical services. It was also found that CPR was more commonly given by a bystander in public, than when an arrest occurred in the patient's home, although health care professionals are responsible for more than half of out-of-hospital resuscitation attempts. This is supported by further research, which suggests that people with no connection to the victim are more likely to perform CPR than a member of their family.
There is also a correlation between the cause of arrest and the likelihood of bystander CPR being initiated. Lay persons are most likely to give CPR to younger cardiac arrest victims in a public place when it has a medical cause; victims in arrest from trauma, exsanguination or intoxication are less likely to receive CPR.
Finally, it has been claimed that there is a higher chance of CPR being performed if the bystander is told to only perform the chest compression element of the resuscitation.
Studies have shown the importance of immediate CPR followed by defibrillation within 3–5 minutes of sudden VF cardiac arrest improve survival. In cities such as Seattle where CPR training is widespread and defibrillation by EMS personnel follows quickly, the survival rate is about 30 percent. In cities such as New York City, without those advantages, the survival rate is only 1-2 percent.
|Type of Arrest||ROSC||Survival||Source|
|Witnessed In-Hospital Cardiac Arrest||48%||22%|
|Unwitnessed In-Hospital Cardiac Arrest||21%||1%|
|Bystander Cardiocerebral Resuscitation||40%||6%|
|Bystander Cardiopulmonary Resuscitation||40%||4%|
|No Bystander CPR (Ambulance CPR)||15%||2%|
|Defibrillation within 3-5 minutes||74%||30%|
Certain ZOLL defibrillation pads are capable of performing similar function, in that they may display rate and depth of compressions. Additionally, a certain algorithm allows them to monitor electrical activity even during CPR (" see-thruCPR").
Another system called the AutoPulse is electrically powered and uses a large band around the patients chest which contracts in rhythm in order to deliver chest compressions. This is also backed by clinical studies showing increased successful return of spontaneous circulation.
It is important to note that CPR techniques portrayed on television and in film are purposely incorrect. Actors performing simulated CPR will keep their elbows bent, to prevent force from reaching the fictional victim's heart. As well as causing significant local trauma, in theory performing CPR on healthy persons may disrupt heart rhythms.