Science Fair Project Encyclopedia
The medical term for this condition is cardiac arrest or, if the patient still has a pulse, respiratory arrest (the combined term cardiorespiratory arrest is also used). The most common treatable cause of cardiac arrest outside of a hospital is a heart attack leading to a heart rhythm disturbance. CPR can be used for cardiac or respiratory arrest due to drowning, drug overdoses and poisoning, electrocution and any other conditions featuring similar symptoms.
Even when performed correctly, CPR can injure the person it is performed on (this is normal, and people should not hesitate to do CPR out of the fear of hurting someone as someone in cardiac arrest does need CPR) and it is never guaranteed to save someone's life. CPR should only be performed on a person in cardiac arrest (no signs of circulation) or on a CPR manikin. Those wishing to learn and perform CPR should take CPR training from a qualified instructor. Reading the Wikipedia is not a substitute for first aid training. Moreover, since the Wikipedia may be altered by anyone at anytime, some parts of the article may be inaccurate.
Heart action and respiratory effort are absolute requirements in transporting oxygen to the tissues. The main organ to suffer from oxygen starvation is the brain, which may sustain irreversible damage after about five minutes. The heart also rapidly loses the ability to maintain a normal rhythm. 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.
CPR is commonly taught to ordinary people who may be the only ones present in the crucial few minutes before emergency personnel are available.
CPR is almost never effective if started more than 15 minutes after collapse because permanent brain damage has probably already occurred. A notable exception is cardiac arrest occurring with exposure to very cold temperatures. A patient cannot be pronounced dead before he has been brought back to a normal temperature by appropriate means: Hypothermia seems to protect the victim somewhat. There are cases where CPR, defibrillation, and advanced warming techniques have revived hypothermia victims after over 30 minutes.
CPR was developed by Peter Safar in the 1950s, and he wrote the book ABC of resuscitation in 1957. It was first promoted as a technique for the public to learn in the 1970s. Early marketing efforts oversold the effectiveness of CPR in rescuing heart attack and other victims. The standards for CPR in the United States are established by the American Heart Association. Rewritten every several years, most recently in 2000, these standards now have a more conservative view of the potential of bystander CPR and stress the importance of immediate defibrillation.
CPR for adults
CPR is best performed by someone who has received training, but generally it would be unwise to wait for such a person to arrive before commencing CPR. Adult CPR is also appropriate for children over 8 years old. Child CPR (below) is indicated for children smaller than an average 8-year-old.
Assessing the situation
The first step in a CPR scenario is to ensure that there is no ongoing danger to any person involved before the patient is approached. The cause of a first accident may cause a second one. This may include:
- Poisonous gas or live electric wires
- Ongoing traffic
- Explosives or inflammable materials (this would make defibrillation dangerous)
Approaching the patient
The person attempting CPR approaches the patient visibly and announces his/her role and offers help. Direct questions ("Can you hear me?", "What happened?", "Where are you hurt?") or instructions ("Open your eyes!") are favoured. Most recommend announcing to the patient that he/she will be touched ("I am going to touch your shoulder, all right?"); the rescuer can take the hand of the patient and ask him to squeeze his hand, in case the patient is conscious but too weak, or incapable, to speak.
If the casualty responds and there are no safety issues, more time is available to summon help as needed.
If there is no response (patient unconscious), a single rescuer will generally need to call for help before commencing CPR.
Calling for help
Anyone who can be involved may call for help and report an unconscious patient. The primary rescuer may need to do this him/herself if no others are available. Rescue services will generally require the following information:
- Name of the person calling
- Place and originating telephone number/radio bandwidth
- Presence of an unconscious patient and other important safety issues (e.g. obvious large volume of blood loss, head injury, burns)
A for Airway
Quick inspection of the mouth may reveal a blocked airway. If possible, the patient should be placed on his/her back on a firm surface. The next step is to get a further view of the mouth and throat, and to make as much space for breathing as possible:
- In the possibility of a neck injury, lifting the chin or jaw may be enough to stabilise the airway;
- In other cases, tilting the head back will lift the tongue away from the back of the mouth, opening the airway.
B for Breathing
After opening the victim's airway, breathing effort is checked. Placing one's cheek in front of the victim's mouth (about 3-5 cm away), while looking at the chest and gently putting one's hand on the chest of the patient, should allow one to detect any of the following signs:
- feeling the airflow on the cheek
- hearing the airflow
- feeling the chest rise and fall
- seeing the chest rise and fall
This is done for 10 seconds. If there is no breathing, artificial respiration is commenced. Both the abdomen and the chest should rise and fall together.
If the victim is breathing, he/she is placed on the side (in the recovery position) and covered the patient. More time is now available to call for help. The absence of breathing effort is a further reason to summon emergency medical services (or to update them that the patient is not breathing) and to start mouth-to-mouth breathing. If there is a public access defibrillator nearby, a bystander may be able to fetch it.
Rescue breathing is the act of mechanically forcing air into a patient's respiratory system; it is only indicated in respiratory arrest, and not in a weakly breathing patient. Ideally, one should never blow into an unknown body for fear of projections of bodily fluids (blood, vomit, etc); thus, a CPR mask or even a cotton handkerchief would be better to protect the rescuer.
Initially, two rescue breaths are given. In rare cases these can help a nearly breathing patient recover spontaneous respiration.
- Tilt back the head of the patient to extend his airway. In most unconscious patients, the jaw will fall open.
- Use two fingers to lift the chin. This will lift the casualty's tongue and stop it blocking the airway.
- In some cases (like some cases of epilepsy), the muscles of the patients are so contracted that it is impossible to open the mouth. Note that the patient will not "swallow" their tongue, contrary to urban legend. If breathing into the mouth is impossible because of a clenched jaw, seal the lips closed and instead breath into the nostrils.
- Close the nose of the patient with your free hand
- take a deep breath, put your mouth on the mouth of the patient in an airtight manner, and blow into the mouth of the patient slowly and gently for no more than 2 seconds. Do not try to inflate the lungs like a balloon, breaths should be gentle to prevent air from entering the stomach.
When you have given two rescue breaths, check for signs of circulation (check the carotid pulse if that is what you have been taught to do), while keeping an eye on his respiration. Chances are that
- the patient might have recovered spontaneous respiration thanks to your rescue breaths
- the patient might be in a state of cardio-respiratory arrest
If the patient has recovered spontaneous respiration, put him in the recovery position, cover him, and monitor his respiration on a regular basis until a mobile medical unit arrives.
If the patient is in a state of cardio-respiratory arrest, you will have to perform CPR.
If you are on your own, and the casualty's condition is obviously the result of injury, drowning, or choking, perform CPR for a minute, and then go and get help. For any other adult casualty, go and get help yourself immediately if you find that breathing is absent. When you return to the patient begin this procedure again, starting with opening the airway.
If breath does not reach the lungs (victims' chest does not rise), probable causes are:
- The victim's tongue is still obstructing the airway. You need to repeat the chin lift and head tilt. This is by far the most common explanation.
- Air is escaping elsewhere. You need to make sure you are sealing around the mouth and pinching the nose fully.
- There is a foreign body obstructing the airway. In this situation, reposition their head and look in the mouth for obstructions. Try to give up to three more breaths. If these do not cause the chest to rise you will need to perform Abdominal thrusts. This may force an obstruction from the windpipe into the mouth. After 15 thrusts, look for and remove any foreign objects in the mouth, and then try to give two rescue breaths. If they go in, assess the casualty's circulation and act as appropriate. If they do not go in, try 15 thrusts again.
- If the breaths do go in and if there is a pulse, continue rescue breathing at a rate of 1 every 5-6 seconds (10-12/min).
If you did not tilt the head because of possible neck injury but the breaths are still not entering the lungs, tilt the head anyway. The victim will certainly die without air in their lungs.
C for Circulation
Methods of checking for circulation vary, and are taught in line with the accepted teaching in a particular organisation or country. In the United Kingdom, a layperson is advised not to check the pulse but to check for signs of circulation such as colour in the skin or movement like breathing, coughing or twitching, for no more than 10 seconds.
If students are trained to take the casualty's pulse, it is performed as follows.
To check for a pulse place your fingers on the victim's Adam's Apple and slide them to the side until you find a groove in the neck above the carotid artery. Check for pulse for no more than ten seconds.
Pulse can also be found in the wrists and the ankles, although in an emergency situation there is not usually time to check for pulse here. On infants it can be found on the inside of the upper arm.
If there is no breathing, coughing or movement after the rescue breaths but there is circulation, continue rescue breathing. Check for signs of circulation regularly, the patient might fall into cardiac arrest any time.
The American Heart Association notes that agonal respirations should not be confused with normal breathing or signs of circulation. Agonal respirations are sometimes seen in cardiac arrest victims and is a physiological reflex to the lack of oxygen. They are characterized by infrequent gasping breaths. If agonal respirations are seen, they should be ignored and CPR promptly started if no signs of circulation are detected.
If there is no circulation:
Send a bystander to call for help using the emergency telephone number. Tell the bystander something like:
- Call for an ambulance. Tell them we're at [your current location] and there is one victim about [victim's approximate age] who is a state of cardiac arrest. Come back as soon as you have done that. Will you do that ?
Even if alert has already be given, this will help the medical unit better prepare their intervention.
Begin chest compressions:
- Place the victim on their back on a firm surface. (a soft surface will render the compression completely useless).
- Kneel next to the victim's chest.
- Remove, open or cut the patient's excess clothes. CPR must be performed close to the patient’s chest (although doing CPR through a t-shirt or similar thin clothing is acceptable).
- Place your hands directly above the sternum, one on top of the other, two fingers' width above the point where the lower ribs meet. To avoid injuring ribs, only the heel of your hand should touch the chest. (The American Heart Association suggests using the CPR landmark described as, "in the center of the chest, between the nipples".)
- Shift your weight forward on your knees until your shoulders are directly over your hands.
- Keeping your elbows locked straight, repeatedly bear down and then come up, bear down and come up. You must depress the chest of an average adult about 2 inches (4-5cm) with each compression. It is important to release completely after each chest compression.
- Compress the chest about 100 times every minute. To get the right speed and rhythm, count out loud as you do the compressions, saying "1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5". Try to compress and release for equal periods of time.
- After each 15 compressions, give the victim 2 rescue breaths (see B for Breathing)
- Return to the victim's chest and put your hands in the correct position again.
- Repeat this cycle of 15 and 2 for a total of 4 times every minute.
Continue until there is:
- breathing, coughing or movement or other signs of circulation return
- qualified help arrives and you are asked to stop (if a defibrillator arrives, its operation will have priority on the CPR).
- you are too exhausted to continue.
Common mistakes in performing chest compressions include rocking back and forth and bending the elbows. It is also important to note that, particularly in elderly patients, crepitations will often occur. Crepitations are the shattering of bones in the rib cage and sternum. They can be both heard and felt. Do not discontinue CPR due to crepitations, although check your hand position if bone breakage appears to be excessive.
In some places, including the UK and the United States, some experts no longer advise laypersons to assess the carotid pulse because it wastes time and studies have shown it leads to an incorrect conclusion in up to 50% of cases. Instead they recommend looking for other visible signs of circulation. Health professionals are still advised to perform a carotid pulse check, taking no more than 10 seconds, whilst also checking the other signs of a circulation.
D for Defibrillation
For cardiac arrest following a heart arrhythmia (which can occur after a heart attack, electrocution, electroltye imbalance), defibrillation is the most effective treatment. CPR is not usually effective on its own, but since defibrillation is rarely available within four to five minutes of cardiac arrest, bystander CPR remains essential in preventing oxygen deprevation damage to the heart and brain. New research indicates that when a person has been in prolonged cardiac arrest and a defibrillator arrives, two to three minutes of CPR before attempting defibrillation improves the victim's prospects (Weisfeldt 2004).
Automated external defibrillators are placed in busy public places such as malls and office buildings or in hard-to-reach locations such as ships and aircraft. They are therefore referred to as public access defibrillators. In most countries, police units also carry them. You might thus be able to perform precise defibrillation before the arrival of the medical units.
The probability of a successful defibrillation starts at 90% immediately after the cardiac arrest, and decreases by ten percents every minute. After ten minutes of CPR without defibrillation, chances of survival are low. Without CPR, chances of survival drop dramatically after only two minutes. You should perform CPR to the best of your ability until a trained medical professional (for example, a paramedic) is available to assess the casualty's condition.
CPR for children age twelve months to eight years
The method of CPR for children is similar to that used for adults. However there are some differences, as children have less lung capacity and a somewhat faster respiration rate. Also, compressions should be considerably less forceful than those used on adults.
A conscious child struggling to breathe will often find the best position to keep a partially obstructed airway open and should be allowed to maintain that position until medical help is available. If the young victim is unresponsive, position the child or infant on the back on a firm, flat surface and begin CPR.
- For Airways: place your hand on the child's forehead and gently tilt the head slightly backward to open the airway. Augment the head tilt by placing 1 or 2 fingers from the other hand under the chin and gently lifting upward. Note that when opening the airway, a child's head should not be tilted as far back as you would an adult's.
- For Breath: Give two effective rescue breaths, in the same manner as you would for an adult. However, remember that an infant will need much less air than a larger child or an adult would. A proper amount of air will move the chest up and down between breaths. A slow, deliberate delivery will reduce the likelihood of forcing air into the stomach, causing distension. Rescue breathing is the single most important maneuver in rescuing a nonbreathing child or infant. If repeated rescue breathing attempts do not result in airflow into the lungs, evidenced by chest movement, a foreign body obstruction should be suspected.
- For Circulation, as discussed in the section on adult CPR, either check for circulation by checking a pulse or alternatively by checking for obvious signs of life, according to your training. In children over one year old, the pulse can be felt at the side of the neck. To check the pulse: while maintaining the head tilt with one hand, find the windpipe at the level of the Adam's apple with two fingers of the other hand. Slide the fingers into the groove between the windpipe and neck muscles, as for adults.
If the child is over 1 year of age, compression is applied to the breastbone by the heel of one hand, located in the midline, 2 fingers'-breadth above the tip of the breastbone (just below the imaginary line between the two nipples). With one hand, the chest is compressed to about one third of the depth of the chest (the exact distance depends on the size of the child) at a rate at about 100 compressions per minute, as for an adult. Compression and relaxation time should be equal and the rhythm smooth and even. The fingers must be kept off the chest.
While the 5:1 ratio has been used in the U.S. for decades "because oxygen is more important for children," a March 2002 study by Norwegian Air Ambulance recommends that children and infants receive the same 15:2 ratio as adults, because the 5:1 approach provides exactly the same number of breaths per minute in actual practice, but fewer chest compressions, since a substantial amount of time is lost due to switching positions.
CPR for infants
Infants under twelve months of age have significantly higher pulse and respiration rates than adults. CPR must be modified significantly to account for the differences.
Tilting the head and lifting the chin will not work in infants, as they have little or no neck. The infant should be cradled in the dominant arm, with the head resting in the rescuer's palm. As in children, the compression/respiration ratio should be 5:1, not 15:2 as in adults.
Respirations are easiest if performed with the mouth covering the entire nose and mouth, and should be given in short puffs of air and not full exhalations. Chest compressions should be delivered at a rate of at least one hundred per minute using two fingers on the sternum at the nipple line, with a compression depth of half an inch to an inch depending on the size of the child.
CPR training is available through many commercial, volunteer and governmental organizations worldwide, including the American Red Cross, American CPR Training, the National Heart Association and St. John Ambulance.
CPR is a practical skill and needs to be regularly practiced on a resuscitation manikin to ensure full competency. Where knowledge of CPR is a job requirement, six monthly refresher courses are recommended.
CPR training should not be confined to just the medical professionals. Almost anyone is able to perform CPR: early CPR is essential in preventing brain damage during a cardiac arrest until a defibrillator or other medical help arrives.
Myths and Popular Culture
Several medical studies have indicated that CPR is inaccurately portrayed in the media: it is commonly described on television and movies as the definitive treatment of cardiac arrest and leads the general public to believe that CPR alone can have an extraordinary resuscitation save rate.
The truth remains that while CPR is an integral part of the resuscitation process, it cannot be used to replace other resuscitative adjuncts such as defibrillation, airway management and intravenous drug therapy. While CPR prevents brain damage by circulating oxygen throughout the body, it does not restart the heart, nor can it be done forever. Therefore, it is very unlikely for someone to resuscitate another person with CPR only, unless in very special circumstances. Usually if someone "regains" signs of circulation after only bystander CPR was performed, it is usually because the victim was not actually in true cardiac arrest.
Many rescuers who have performed CPR—healthcare provider and layperson alike—have indicated their surprise about what it is really like to perform CPR. Some note that they were unprepared for cartilage separation (considered to be normal in some cases) during chest compression, and believed that they were performing CPR incorrectly (when they were not). Others note that they were shocked when patients vomited, a stark contrast to the clean environment CPR was taught to them in classes. In some cases, rescuers blamed themselves when patients were not resuscitated, believing it was their fault for doing “CPR incorrectly” or “not doing CPR well enough”.
It is important to educate the general public and healthcare professionals that CPR is never guaranteed to save someone's life. People need to know that even if CPR is performed perfectly, the person in cardiac arrest may still not be resuscitated. The American Heart Association notes that "some hearts are too sick to be saved" and reflects the reality that CPR is not a cure-all but merely an important part of the resuscitation process. Rescuers who perform CPR should never be blamed for a patient's death because of "inadequate CPR": it is not CPR's goal to "save" someone, but only to maintain the heart and brain until more advanced medical help arrives to provide basic life support and advanced cardiac life support. CPR itself is an inexact and evolving science.
Continue CPR until help arrives or your life is placed in danger by continuing to perform CPR.
See also wilderness first aid for situations where it may be impossible to continue CPR and guidelines for how to proceed in such a situation.
- Weisfeldt ML. Public access defibrillation: good or great? BMJ USA 2004;328:E271-E272. Fulltext. PMID 14988214.
- How to do CPR on an adult : easy to understand instructions from eHow.com
- How to do CPR on a child
- CPR for an infant : clear and concise instructions.
- Circulation. 1997;95:2174-2179 Current American Heart Association Single-rescuer adult basic life support
- European Resuscitation Council includes the European 2000 guidelines
- UK Resuscitation Council
- Open Directory: CPR and First Aid Training
- Learn CPR - Site with basic description of CPR procedure
- BBC First Aid Action - includes some information about CPR
- Open Directory: CPR websites
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