Human Cardiovascular system - Cardiopulmonary-Resuscitation-(CPR)
(CPR) is an emergency procedure for people in cardiac arrest or, in some circumstances, respiratory arrest. CPR is performed in hospitals and in the community. CPR involves physical interventions to create artificial circulation through rhythmic pressing on the patient!!!s chest to manually pump blood through the heart, called chest compressions, and usually also involves the rescuer exhaling into the patient (or using a device to simulate this) to inflate the lungs and pass oxygen in to the blood, called artificial respiration. Some protocols now downplay the importance of the artificial respirations, and focus on the chest compressions only. CPR is unlikely to restart the heart; its main 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. Advanced life support and defibrillation, the administration of an electric shock to the heart, is usually needed for the heart to restart. This only works for patients in certain heart rhythms, namely ventricular fibrillation or pulseless ventricular tachycardia, rather than the !!!flat line!!! asystolic patient although CPR can help induce a shockable rhythm in an arrested patient. CPR is generally continued, usually in the presence of advanced life support (such as from EMS providers), until the patient regains a heart beat (called "return of spontaneous circulation" or "ROSC") or is declared dead.
The main indication for CPR is cardiac arrest (a condition in which a person!!!s heart has stopped). CPR is used on people 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 one to two 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 seven 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 near-drownings 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.
In 2005, CPR guidelineswere published by the International Liaison Committee on Resuscitation (ILCOR), agreed at the 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. The primary goal of these changes was to simplify CPR for lay rescuers and healthcare providers alike, to maximize the potential for early resuscitation. The important changes for 2005 were:
- A universal compression-ventilation ratio (30:2) recommended for all single rescuers of infant (less than one year old), child (1 year old to puberty), and adult (puberty and above) victims (excluding newborns).The primary difference between the age groups is that with adults the rescuer uses two hands for the chest compressions, while with children it is only one, and with infants only two fingers (index and middle fingers).While this simplification has been introduced, it has not been universally accepted, and especially amongst healthcare professionals, protocols may still vary.
- The removal of the emphasis on lay rescuers assessing for pulse or signs of circulation for an unresponsive adult victim, instead taking the absence of normal breathing as the key indicator for commencing CPR.
- The removal of the protocol in which lay rescuers provide rescue breathing without chest compressions for an adult victim, with all cases such as these being subject to CPR.
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.
Compression only Resuscitation
The traditional International Liaison Committee on Resuscitation approach described above has been challenged in recent years by advocates for compression-only CPR, also known as cardiocerebral resuscitation (CCR). This technique is simply chest compressions without artificial respiration. The respiration component of CPR has been a topic of major controversy over the past decade. The CCR method has been championed by the University of Arizona!!!s Sarver Heart Center. A study by the university claimed a 300% greater success rate over standard CPR. The exceptions were in the case of drowning or drug overdose. 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 Compressions
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.
Internal cardiac massage
Internal cardiac massage is the process of cardiac massage carried out through a surgical incision into the chest cavity. This distinguishes the process from conventional, external cardiac massage, which is carried out by compression near the sternum during cardiopulmonary resuscitation.
A form of "self-CPR" termed "Cough CPR" was the subject of a hoax chain e-mail entitled "How to Survive a Heart Attack When Alone" which wrongly cited "ViaHealth Rochester General Hospital" as the source of the technique. Rochester General Hospital has denied any connection with the technique. Rapid coughing has been used in hospitals for brief periods of cardiac arrhythmia on monitored patients. One researcher has recommended that it be taught broadly to the public. However, ï¿½cough CPRï¿½ cannot be used outside the hospital because the first symptom of cardiac arrest is unconsciousness in which case coughing is impossible, although myocardial infarction (heart attack) may occur to give rise to the cardiac arrest, so a patient may not be immediately unconscious. 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 ï¿½cough CPRï¿½ 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."
Used alone, CPR will result in few complete recoveries, and those who do survive often develop serious complications. Estimates vary, but many organizations stress that CPR does not "bring anyone back," it simply preserves the body for defibrillation and advanced life support. However, in the case of "non-shockable" rhythms such as Pulseless Electrical Activity (PEA), defibrillation is not indicated, and the importance of CPR rises. On average, only 5%-10% of people who receive CPR survive. The purpose of CPR is not to "start" the heart, but rather to circulate oxygenated blood, and keep the brain alive until advanced care (especially defibrillation) can be initiated. As many of these patients may have a pulse that is impalpable by the layperson rescuer, the current consensus is to perform CPR on a patient who is not breathing. Studies have shown the importance of immediate CPR followed by defibrillation within 3ï¿½5 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. In most cases, there is a higher proportion of patients who achieve a Return of Spontaneous Circulation (ROSC), where their heart starts to beat on its own again, than ultimately survive to be discharged from hospital (see table below). This is due to medical staff either being ultimately unable to address the cause of the arrhythmia or cardiac arrest, or in some instances due to other co-morbidities, due to the patient being gravely ill in more than one way.
|Type of Arrest||ROSC||Survival|
|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 3ï¿½5 minutes||74%||30%|
ROSC = Return of spontaneous circulation
Chest compression adjuncts
Several devices have become available in order to help facilitate rescuers in getting the chest compressions completed correctly. These devices can be split in to three broad groups - timing devices, those that assist the rescuer to achieve the correct technique, especially depth and speed of compressions, and those which take over the process completely.
They can feature a metronome (an item carried by many ambulance crews) in order to assist the rescuer in getting the correct rate. The CPR trainer cited here has timed indicators for pressing on the chest, breathing and changing operators.
Manual assist devices
Studies have shown that audible and visual prompting can improve the quality of CPR and prevent the decrease of compression rate and depth that naturally occurs with fatigue, and to address this potential improvement, a number of devices have been developed to help improve CPR technique. These items can be devices to placed on top of the chest, with the rescuers hands going over the device, and a display or audio feedback giving information on depth, force or rate, or in a wearable format such as a glove. Several published evaluations show that these devices can improve the performance of chest compressions. As well as use during actual CPR on a cardiac arrest victim, which relies on the rescuer carrying the device with them, these devices can also be used as part of training programmes to improve basic skills in performing correct chest compressions. Certain defibrillation pads are capable of performing similar function, in that they may display rate and depth of compressions. Additionally, a certain algorithm may allow them to monitor electrical activity even during CPR.
There are also some devices available which take over the chest compressions for the rescuer. These devices use techniques such as pneumatics to drive a compressing pad on to the chest of the patient. One such device, known as the LUCAS, was developed at the University Hospital of Lund, is powered by the compressed air cylinders or lines available in ambulances or in hospitals, and has undergone numerous clinical trials, showing a marked improvement in coronary perfusion pressure and return of spontaneous circulation. 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.
Chance of receiving CPR
Various studies suggest that in out-of-home cardiac arrest, bystanders, lay persons or family members attempt CPR in between 14% and 45% of the time, with a median of 32%. This indicates that around 1/3 of out-of-home arrests have a CPR attempt made on them. However, the effectiveness of this CPR is variable, and the studies suggest only around half of bystander CPR is performed correctly. 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. This is likely because of the shock experienced by finding a family member in need of CPR; it is easier to remain calm - and think clearly - when the person in need of CPR is a complete stranger, as in this case one will not be as frightened. 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.
Chance of receiving CPR in time
CPR is only likely to be effective if commenced within 6 minutes after the blood flow stops, because permanent brain cell damage occurs when fresh blood infuses the cells after that time, since the cells of the brain become dormant in as little as 4ï¿½6 minutes in an oxygen deprived environment and the cells are unable to survive the reintroduction of oxygen in a traditional resuscitation. Research using cardioplegic blood infusion resulted in a 79.4% survival rate with cardiac arrest intervals of 72ï¿½43 minutes, traditional methods achieve a 15% survival rate in this scenario, by comparison. New research is currently needed to determine what role CPR, electroshock, and new advanced gradual resuscitation techniques will have with this new knowledge .A notable exception is cardiac arrest occurring in conjunction with exposure to very cold temperatures. Hypothermia seems to protect the victim by slowing down metabolic and physiologic processes, greatly decreasing the tissues!!! need for oxygen. There are cases where CPR, defibrillation, and advanced warming techniques have revived victims after substantial periods of hypothermia.
Chest compressions are capable of causing significant local blunt trauma, including bruising or fracture of the sternum or ribs. Performing CPR on a healthy person may or may not disrupt normal heart rhythm, but regardless the technique should not be performed on a healthy person because of the risk of trauma. The portrayal of CPR technique on television and film often is purposely incorrect. Actors simulating the performance of CPR may bend their elbows while appearing to compress, to prevent force from reaching the chest of the actor portraying the victim. Other techniques, such as substituting a mannequin torso for the "victim" in some shots, may also be used to avoid harming actors. History 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, resting on the palms of both hands. Upward pressure applied at the patientï¿½s elbows raised the upper body while pressure on their back forced air into the lungs, essentially the Silvester Method with the patient flipped over. This method would continue to be shown, for purposes, side-by-side with modern CPR in the Boy Scout Handbook until its ninth edition in 1979. The technique was later banned from first-aid manuals in the UK. 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 Kouwenhoven and Joseph S. Redding had recently discovered the method of external chest compressions, whereas Safar had worked with Redding and 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 by Redding, Safar and JW Perason. Soon afterwards, the technique 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. Artificial respiration 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