pertaining to the heart and lungs. cardiopulmonary resuscitation (CPR) the manual application of chest compressions and ventilations to patients in cardiac arrest, done in an effort to maintain viability until advanced help arrives. This procedure is an essential component of basic life support (BLS), basic cardiac life support (BCLS), and advanced cardiac life support (ACLS).The preliminary steps of CPR, as defined by the American Heart Association, are (1) calling for help; (2) establishing unresponsiveness in the victim by tapping or gently shaking and shouting at him or her; (3) positioning the victim in a supine position on a hard surface; (4) giving two breaths; and (5) checking the pulse. These are begun as quickly as possible; prompt action is essential for successful outcome. At the moment breathing and heart action stop, "clinical death" ensues. Within four to six minutes the cells of the brain, which are the most sensitive to lack of oxygen, begin to deteriorate. If breathing and circulation are not restored within this period of time, irreversible brain damage occurs and "biological death" takes place.Although CPR is strongly recommended as a life-saving measure, it is not without danger; specific risks include rib fracture, damage to the liver or heart, and puncture of lungs or large blood vessels. All health care providers should receive instruction and practice in CPR under the direction of a qualified instructor. The public in general should also be encouraged to learn CPR for use in emergency situations.Once it has been established that a person is in need of CPR, the rescuer immediately begins the "ABC's" of CPR: Airway, Breathing, and Circulation. Opening the airway and determining by look, sound, and feel is the first step for determining whether the person will be able to resume unassisted breathing. This is accomplished by lifting the chin up and back and bringing the mandible forward. If there is no evidence of spontaneous breathing, the rescuer corrects obstruction of the airway by a foreign body, when this is indicated. This is done by one or more of the following methods: back blows, manual chest thrusts, and finger sweeps. Once the airway is open, rescue breathing is started by means of mouth-to-mouth resuscitation (see artificial respiration).The third element of CPR is circulation, which begins by establishing the presence or absence of a pulse. If there is no pulse, compression of the chest is begun. This consists of rhythmic applications of pressure on the lower half of the sternum (NOT on the xiphoid process, which may injure the liver). For a normal-sized adult, sufficient force is used to depress the sternum about 4 to 5 cm (1½ to 2 in). This raises intrathoracic pressure and produces the output of blood from the heart. When the pressure is released, blood is allowed to flow into the heart. Compressions should be maintained for one-half second; the same length of time is allowed for the relaxation period.Chest compression is always accompanied by rescue breathing. The two must be coordinated so that there is regular and uninterrupted circulation of blood and aeration of the lungs.CPR is a psychomotor skill and all health care providers should keep their certification current in order to be proficient in this procedure in case of emergency. The techniques of CPR provide basic life support (BLS) in all cases of respiratory and cardiac arrest. Standards and guidelines for CPR and emergency cardiac care (ECC), including BCLS and ACLS, have been developed cooperatively by the American Heart Association and the National Academy of Sciences-National Research Council. Reprints of these standards can be obtained from local chapters of the American Heart Association or from the American Heart Association, Distribution Department, 7272 Greenville Ave., Dallas, TX 75231-4596, telephone (800) 553-6321.Cardiopulmonary resuscitation. Airway: One hand is placed under the neck to extend it. With the other hand the chin is lifted so that it points upward. Sometimes this maneuver clears the airway and is all that is necessary to reinstate spontaneous breathing. Breathing: The nostrils are pinched and the chin held in position so that the rescuer's mouth can make a tight seal over the victim's mouth. Circulation: Compression of the chest with a downward thrust is alternated with breathing. If one person is performing CPR, he or she first blows into the victim's lungs, applies pressure to the sternum 15 times, and then continues a cycle of 2 breaths to 15 compressions. Cardiopulmonary resuscitation. Airway: One hand is placed under the neck to extend it. With the other hand the chin is lifted so that it points upward. Sometimes this maneuver clears the airway and is all that is necessary to reinstate spontaneous breathing. Breathing: The nostrils are pinched and the chin held in position so that the rescuer's mouth can make a tight seal over the victim's mouth. Circulation: Compression of the chest with a downward thrust is alternated with breathing. If one person is performing CPR, he or she first blows into the victim's lungs, applies pressure to the sternum 15 times, and then continues a cycle of 2 breaths to 15 compressions. Cardiopulmonary resuscitation. Airway: One hand is placed under the neck to extend it. With the other hand the chin is lifted so that it points upward. Sometimes this maneuver clears the airway and is all that is necessary to reinstate spontaneous breathing. Breathing: The nostrils are pinched and the chin held in position so that the rescuer's mouth can make a tight seal over the victim's mouth. Circulation: Compression of the chest with a downward thrust is alternated with breathing. If one person is performing CPR, he or she first blows into the victim's lungs, applies pressure to the sternum 15 times, and then continues a cycle of 2 breaths to 15 compressions. Cardiopulmonary resuscitation. Airway: One hand is placed under the neck to extend it. With the other hand the chin is lifted so that it points upward. Sometimes this maneuver clears the airway and is all that is necessary to reinstate spontaneous breathing. Breathing: The nostrils are pinched and the chin held in position so that the rescuer's mouth can make a tight seal over the victim's mouth. Circulation: Compression of the chest with a downward thrust is alternated with breathing. If one person is performing CPR, he or she first blows into the victim's lungs, applies pressure to the sternum 15 times, and then continues a cycle of 2 breaths to 15 compressions.