The Advent of Cardiopulmonary Resuscitation (CPR)

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The Advent of Cardiopulmonary Resuscitation (CPR)

Overview

Cardiopulmonary Resuscitation (CPR) is an emergency first aid procedure designed to re-establish or simulate heart and lung action. During cardiac arrest, CPR provides a percentage of oxygenated blood to the heart and brain, helping to keep these organs alive until advanced life support is provided. CPR techniques focus on the "ABCs" of resuscitation—Airway, Breathing, and Circulation. Modern CPR was introduced in the medical community in the late 1950s, and is delivered using rescue breathing and chest compressions. The advent of CPR contributed to fundamental changes in the delivery of medical care, created ethical end-of-life considerations, and influenced outlook on health and fitness.

Background

During the 1950s, American physicians James Elam and Peter Safar were the first contemporary researchers of the airway "A" and breathing "B" components of CPR. Elam doubted the methods then-in-use for artificial respiration, which included the use of arm lifts and slow pressure applied to the chest. Elam proposed that expired air given directly to the victim through mouth-to-nose breathing would provide more oxygen to the body. Elam then demonstrated that his own expired air could maintain normal arterial oxygen levels in surgical patients when blown through their endotracheal tubes. Elam published his findings in 1954, and traveled to lobby governmental agencies and colleagues, championing the simplicity of his technique.

Safar, while sharing a long car ride home from an anesthesia conference with Elam, also became interested in resuscitation research. In a series of experiments on human volunteers begun in 1956, Safar focused on mouth-to mouth resuscitation. He found that mouth-to-mouth resuscitation techniques provided superior lung ventilation than the existing manual maneuvers. Safar demonstrated the ease of learning and performing mouth-to-mouth resuscitation techniques. Additionally, Safar addressed the issue of airway obstruction which often accompanies unconsciousness, showing that simply tilting the head backward and the jaw upward usually opens the airway. In 1958, Safar's research was published, and the medical community adopted Safar's mouth-to-mouth resuscitation methods. The American Medical Association called mouth-to-mouth resuscitation "an easily learned life-saving procedure" and encouraged that "information about expired air breathing be disseminated as widely as possible."

The discovery of artificial circulation was accidental, and actually a rediscovery of techniques similar to external cardiac massage described in late nineteenth-century medical literature. At that time, external cardiac massage was not accepted, and remained forgotten for over half a century. Instead, surgeons practiced open cardiac massage, in which the physician simulated circulation by squeezing the heart with his hand, as the preferred treatment for cardiac arrest until the 1950s. The circulation "C" component of CPR was rediscovered by two engineering scientists at Johns Hopkins University in 1958. William Kouwenhoven and G. Guy Knickerbocker studied ventricular fibrillation (an inefficient, "quivering" heart rhythm which leads to cardiac arrest) in anesthetized dogs. Knickerbocker noticed a slight momentary rise in blood pressure when defibrillation paddles (an instrument which delivers an electric shock to return the fibrillating heart to an efficient rhythm) were rested on the dog. Through a series of experiments, Kouwenhoven and Knickerbocker, along with surgeon James Jude, learned that when applying pressure straight downward with the heel of the hand to the sternal area of the chest, artificial circulation was most efficient. Through trial and error they also determined the most effective rate of chest compressions (60-80 per minute) and the optimal depth of compressions (1.5-2 inches). After successfully applying their techniques to human patients, the three scientists published their findings in 1960, asserting that cardiac resuscitation could be performed anywhere and "all that is needed is two hands."

Impact

Modern CPR was created in 1960 when the three techniques, mouth-to-mouth resuscitation, the head tilt, and chest compressions, were united. Safar joined Kouwenhoven and Jude to study the merger of the techniques, and together they conducted a world-wide tour to promote CPR to the medical community. American physician Archer S. Gordon, who defined the early manual artificial respiration methods, embraced CPR and contributed the "A, B, C" mnemonic for its airway, breathing, and circulation components. Gordon also helped produce a training film in 1962 which educated millions of medical personnel and students in CPR methods. The American Heart Association formally endorsed CPR in 1963, and founded a committee dedicated to its study. By 1966, the National Academy of Sciences reported recommendations to standardize the performance and training of CPR, allowing CPR to become the standard first-line treatment for hospitalized victims of cardiac arrest. The same year, deaths from cardiac arrest in hospitals began to decline.

Heart disease was the leading cause of death in America by 1960, due in part to Americans' changing lifestyles. Nutritional habits changed as processed, convenience, and fast foods contributed a higher fat and salt content to the diet. Simultaneously, increased urbanization led to a more sedentary lifestyle. As a result, more Americans suffered myocardial infarctions (heart attacks), and most of these occurred outside the hospital. Coupled with trauma suffered from automobile accidents on increasingly crowded roadways, the need for CPR outside the hospital was quickly realized.

In 1966, a national standard for training ambulance personnel was created, which included CPR, and led to the rise of emergency medical technicians (EMTs). EMTs could provide CPR at the scene and en route to the hospital. Often, however, victims of cardiac arrest, despite receiving CPR, arrived at the hospital too late to be saved by advanced life support techniques, including defibrillation. CPR delivery outside of the hospital made defibrillation and advanced life support necessary outside of the hospital as well. The first mobile cardiac care unit in the United States was established in New York in 1968, based on a similar program in Belfast, Northern Ireland. Staffed with doctors, nurses, and technicians, the unit provided medications, CPR, and defibrillation to victims with cardiac emergencies at the scene and during transport to the hospital. Although successful, the program was not practical. As it required a physician to be in attendance, often the unit experienced delays arriving at the scene after waiting for the physician to extricate himself from hospital duties and jump aboard the ambulance. American physician and engineer Eugene Nagel devised a method to deliver advanced emergency care in the field while allowing the physician to monitor the patient from the hospital in 1968. Nagel developed the first portable telemetry machine (used to determine the heart rhythm and relay it to a physician at the hospital) and trained rescue firemen in Miami in its use. In 1969, Nagel's "paramedics" performed CPR on a 60-year-old man, then used the portable defibrillator to shock the fibrillating man's heart back to a normal rhythm. Today, the paramedic system of providing advanced emergency medical care is in use throughout the developed world.

CPR was introduced into the community in 1972 in Seattle. Under Seattle's "tiered response" system, all emergency personnel, including volunteer firefighters, were trained in CPR. The first available personnel unit was assigned to reach the emergency site quickly and provide CPR, followed by the paramedics who initiated advanced life support and transported the patient to the hospital. Seattle physician Leonard Cobb, after analyzing Seattle's emergency response data, found the sooner CPR was started, the more favorable were the chances for survival. Cobb embarked upon an ambitious program to train 100,000 Seattle area citizens in a modified version of CPR, reasoning that bystanders can become the first responders to a medical emergency. Although the medical community was skeptical at first, by 1973 the American Heart Association defined the standards for basic CPR, and by 1974 , the American Red Cross conducted popular CPR classes for the public throughout the Unites States. Community-based CPR continues today as one of America's most farreaching public health initiatives of the twentieth century.

Empowered with the new knowledge of CPR, Americans in the mid-1970s began a period of increased health consciousness. Aerobics, exercising in a manner to build cardio-vascular endurance and fitness, was embraced by many Americans who included aerobic exercise into their regular routine for the first time. Running and, particularly, jogging became popular aerobic pastimes. Health and exercise clubs increased in number, and athletic wear became a fashion trend. Americans became familiar with their individual "cholesterol counts" (fatty acids in the blood which are a risk factor for heart disease), and sought ways to improve them through a plethora of self-help publications on the market. The natural foods trend of the 1960s reemerged, with an emphasis on heart-healthy foods. These trends continue to evolve today. The rate of American deaths from heart disease reached a plateau, then experienced a decline during the 1980s and 1990s. Further innovations in life-sustaining treatment of heart disease as well as lifestyle improvements are credited with the reduction.

The advent of CPR gave rise to ethical questions, both in the hospital and the community. Prior to 1950, cardiac arrest almost always resulted in death. With CPR and advanced life support, medical personnel have greater options and responsibility to deter or determine when death occurs. The precise incidence of CPR effectiveness is not known, and at times those who are saved by CPR require intensive long-term life support. For these reasons, many with advanced disease or age choose not to undergo CPR and advanced life support. Legislation was passed in most states urging medical personnel to honor a patient's "living will" expressing end-of-life choices. Legislation was also refined to protect and encourage bystanders to render first aid, including CPR if needed, to victims in emergency situations. Most hospitals have ethics committees to define standards of life-sustaining and end-of-life care, and assist medical personnel and patients dealing with this issue.

The American Heart Association continues to set the standards for CPR training and performance. Since its inception, revisions to CPR include considerations for administering CPR to a child, an infant, or an injured person. The Heimlich maneuver for aiding a choking victim is included along with the breathing section of CPR training. Following the CPR example, health officials are encouraging many sectors of the public to receive training in advanced life support using the newly developed automatic defibrillator. New methods are under study to increase oxygen to the brain during CPR. The most significant aspect of CPR, however, remains its ability to be easily learned, and performed in almost any location, enabling trained citizens as well as professionals to give aid during critical emergencies.

BRENDA WILMOTH LERNER