What is resuscitation? |

Physiology of Respiration and Circulation

Every cell in the human body needs a constant and steady supply of oxygen. The delivery of oxygen is possible only through a continuous movement of oxygen-rich blood, with the heart and lungs working efficiently together. To survive, the body must have a functioning heart and lungs, or an outside force that makes both organs function artificially. Two major life-threatening conditions include respiratory arrest (cessation of breathing) and cardiac arrest (cessation of heartbeat). Death is certain unless something is done to put oxygen into the blood and circulate it throughout the body. Cardiopulmonary resuscitation (CPR) is the artificial action of putting oxygen into the lungs and making the heart pump blood throughout the body. By understanding the anatomy and physiology of the heart and lungs, and their entire systems, it is easier to see how CPR can help a person who is not breathing and whose heart is not pumping blood.

The respiratory system.
This system has many parts, from the nose down to the smallest sacs of the lungs. After air is taken in through the nose or mouth, it moves farther down into the throat (pharynx), past the larynx (voice box) and the trachea (windpipe). Next, the inhaled air goes through specialized tubes called bronchi, one connected to each lung. From this larger tube, the air passage narrows into smaller tubes called bronchioles. The bronchioles become smaller and end at the air sacs, called alveoli. Alveoli are actually millions of tiny air sacs that allow oxygen to move into the bloodstream and carbon dioxide to be removed from the blood and exhaled. The
alveoli are hollow and surrounded by a very thin, specialized membrane that is only one
or two cells thick. This transfer of needed oxygen, along with the removal of the carbon dioxide waste products, happens through the small capillaries surrounding the alveoli. In the blood, oxygen attaches to the hemoglobin found in red blood cells, and, in return, carbon dioxide crosses back into the lungs in order to be exhaled.

It is this carbon dioxide buildup in the blood that stimulates how deep and how often one breathes. An area of the brain called the medulla is considered the body’s respiratory center because it is responsible for sending electrical signals to the chest
muscles that control breathing. A check-and-balance system monitors the amount of carbon dioxide in the bloodstream. When the level increases, the rate and depth of respirations also increase so that the excess amount can be exhaled.

The brain sends messages via the nerves to the muscles of the ribs. In addition to smaller muscles between each rib, the neck and shoulder muscles must also help during breathing. The diaphragm, a large, sheetlike muscle that separates the chest from the abdominal organs, also plays a major role in inspiration and expiration. The diaphragm extends from front to back by attaching to the lower part of the ribs. During inhalation, the muscles raise the ribs up and forward while the diaphragm moves downward toward the abdominal cavity, thus making room for the lungs to expand. As a result, the pressure inside the lungs becomes less than that of the surrounding air. It is this difference in air pressure, not an actual sucking in of air, that causes air to move into the lungs. The act of exhaling occurs when these muscles relax, causing the ribs to move back down and the diaphragm to rise. The size of the chest cavity decreases, the elastic nature of the lungs causes them to become smaller, and air moves out of the lungs.

The circulatory system. Life cannot be sustained simply by air moving in and out of the lungs. Once the oxygen moves from the tiny air sacs in the lungs and across into the bloodstream, it must be moved to every cell in the body. This transportation is possible because of the
circulation of blood within the many vessels. At the center of this circulatory system, the heart acts as the pump, pushing blood out through the large arteries and the smaller arterioles and capillaries. After reaching the capillaries, the oxygen is delivered to the cells, and waste products such as carbon dioxide are picked up. The capillaries branch into larger venules and then into even larger veins. The major veins, from all areas of the body, return blood to the heart that is no longer rich in oxygen. Instead, it contains carbon dioxide that needs to be removed. It is this lack of oxygen that makes the blood in veins appear bluish, whereas the oxygen-rich blood found in arteries is more red in color.

The heart is responsible for sending out oxygen-carrying blood to all body tissues and moving carbon dioxide-rich blood to the lungs so that it can be exhaled. The right side of the heart is responsible for receiving blood that no longer has enough oxygen, called deoxygenated blood. The blood is next pumped through the bottom half of the heart (right ventricle) into a specialized artery called the pulmonary artery and then into each lung. Although the term “arteries” is usually reserved for vessels carrying blood with high levels of oxygen, there is one exception: The pulmonary artery does not carry oxygen-rich blood. The blood then flows into smaller capillaries surrounding the alveoli in the lungs, where it exchanges carbon dioxide for oxygen. On the return trip to the left side of the heart, after leaving the lungs, the oxygenated blood moves through the pulmonary veins. Blood then travels from the left upper portion of the heart (left atrium) to the left ventricle, which is the major muscle of the heart responsible for pumping blood to all the cells of the body.

In summary, the right side of the heart carries deoxygenated blood from the body to the lungs. The left side of the heart receives the oxygenated blood from the lungs and pumps it throughout the body. The huge network of connections in the circulatory system, from the heart all the way out to the tips of the toes and returning to the heart, makes up a closed system that must not have any large leaks, which occur during bleeding.

Indications and Procedures

It might seem that whether the heart is functioning is not a matter of yes or no, black or white. However, there are many gray areas that represent a heart that is beating but not working in a manner that will support life. These gray areas include many types of abnormal beats, known as
arrhythmias, or abnormal rhythms. If the heart is beating too fast (tachycardia) or extremely slowly (bradycardia), then it cannot supply body tissues with needed oxygenated blood. A constant and even pressure of blood flow must also be maintained.

The amount of pressure inside the circulatory system varies.
Blood pressure is measured as systolic pressure over diastolic pressure. In a blood pressure reading of 120/70, the top number, 120, indicates the amount of pressure on the walls of the vessels when the heart is beating (contracting). The bottom number, 70, reflects the amount of pressure on the vessel walls between beats when the heart is at rest. In cases when both numbers are extremely low or high, the system is not working properly and urgent measures must be taken to identify and fix the problem.

When either the circulatory or the respiratory system is not able to perform properly, the entire body suffers quickly. Without oxygenated blood, brain damage begins within four to six minutes. While sitting, the human heart pumps sixty to one hundred times each minute, moving about 5.5 liters of blood throughout the body every minute. The average 150-pound man has a total of about 6.75 liters of blood that must be kept constantly moving. The heart acts like a pump because it is a special muscle with its own electrical system. Much the same way as a light switch turns on a light bulb, the heart pumps because an electrical message at the top of the heart, in the sinoatrial (S-A) node, makes the entire heart muscle contract. This natural pacemaker keeps the heart beating when all things are in proper working order. If the heart stops beating correctly or the lungs do not work, however, the person will die unless resuscitation is started.

Resuscitation means making the heart pump blood and getting oxygen into and out of the lungs. In an example of the most severe case, a person is found not breathing and without a pulse. Cardiopulmonary resuscitation (CPR) courses teach that the first step is to open the airway and be sure that nothing is blocking the flow of air in and out of the lungs. If a blockage is found, it must be removed immediately. If the person is not breathing, the rescuer must breathe for him or her. Artificial respiration, or mouth-to-mouth ventilation, in which one individual breathes air into another’s mouth, will force oxygen-containing air into the lungs so that it can be picked up in the bloodstream and transported to body cells. Pinching the patient’s nose and blowing into the mouth forces air into the lungs in much the same way as taking a deep breath. Yet this artificial breathing alone is not enough. The oxygen put into the lungs must be moved around the body, which can only be done through circulating blood.

To move the blood through the circulatory system, something must be done to make the heart pump. This can be accomplished through chest compressions. Since the heart lies between the breastbone (sternum) and the spine, it is surrounded by hard, bony structures. By pressing in the correct position, with sufficient pressure and depth, the heart muscle can be squeezed. This squeezing action will result in blood being forced out of the heart and onto its path around the body. The oxygen blown into the lungs will be picked up by the passing blood and moved out to necessary areas of the body.

Even with the use of proper techniques, however, cardiopulmonary resuscitation should only be a temporary measure for a person who has no pulse and who is not breathing. CPR is only a momentary first-aid measure. Yet this procedure is a vital one: Until further medical assistance can be given, it is extremely important that oxygen circulate in the patient’s body.

CPR is usually done by the first responder who finds the victim. This form of resuscitation is known as basic life support (BLS). The administration of BLS is the step just before advanced cardiac life support (ACLS), which offers additional treatment measures given by medically trained personnel. ACLS is given by emergency medical technicians (EMTs), paramedics responding in ambulances, or other health care professionals. While continuing CPR, the medical team will start advanced care before or during the drive to a hospital emergency department.

To provide the proper treatment, paramedics must determine the electrical activity of the heart. The heart’s rhythm is recorded on an electrocardiograph (ECG or EKG) machine, which helps the medical team find the cause of the problem. The portable ECG machine, which is commonly called a cardiac monitor, displays the electrical activity in the heart. When the electrical impulses are not producing a rhythmic beating pattern, various treatment procedures may follow, depending on how the heart is pumping or if it is working at all. It is possible to correct a heart that has an irregular beat caused by abnormal electrical activity. A total lack of electrical activity in the heart is called asystole and is recorded on the monitor as a flat line. The ACLS team can attempt to adjust the abnormal electrical signal but usually cannot mechanically restart a heart that has no electrical impulses. Other heart problems produce other types of tracings on the monitor. In one type of arrhythmia called ventricular fibrillation, the heart has a rapid, chaotic electrical activity that does not allow the heart to beat;
the patient will stop breathing and will have no pulse. In this case, CPR is needed to reduce brain damage caused by decreased oxygen to cells, while paramedics and other health care professionals begin advanced life support in an attempt to reverse the dying process.

Many different protocols exist on how ACLS treatment should progress, and the following is merely one example. In 2005, the American Heart Association made changes in CPR, BLS, and ACLS protocols. The medics may use an electrical machine known as a defibrillator to deliver electrical shocks through the chest and toward the heart in the hope of correcting the rhythm. A single electric shock is given, followed by CPR. A needle and special catheter are placed in a vein to start intravenous (IV) fluids, in which medications can be given to travel to the heart through the veins. A high concentration of oxygen is delivered through a tube inserted through the mouth or nose and passed into the upper part of the lung so that artificial ventilation can aid in the movement of concentrated oxygen. Adrenaline (also known as epinephrine) is given through the IV; this drug will increase the blood flow to the heart and brain by narrowing other vessels and will also increase the heart rate and blood pressure. CPR is continued for two minutes, then a brief pause occurs for another single electric shock. CPR resumes immediately.

Studies of actual resuscitation processes have demonstrated that CPR was often stopped while personnel prepared medications or prepared to defibrillate. These pauses caused the absence of blood flow and oxygen for prolonged periods of time. This observation led to the new guidelines. Single shocks are given, rather than the previous three shocks of increasing voltage. CPR is given continuously except during the actual shock.

The next drug given may be amiodarone, which helps to calm a heart that is beating too fast or erratically. If the irregular rhythm has still not been corrected, then sodium bicarbonate may given to reduce the acids produced in the body because of the lack of oxygen. This entire scenario is repeated until the heart is beating in a manner that will sustain life or it is determined by a physician that the person cannot be resuscitated.

Other drugs that are used for specific heart problems include atropine, lidocaine, vasopressin, procainamide, verapamil, dopamine, and adenosine. All these drugs target specific problems during a cardiac episode. For individuals who are successfully resuscitated and are stable but unresponsive on arrival at the hospital, induced hypothermia is recommended for the first twenty-four hours to improve brain functioning.

When the heart slows or weakens to the point that it is barely beating, life can be artificially maintained in a few cases by using a cardiac pacing unit to create an artificial heartbeat electrically, a procedure called cardiac pacing. This artificial heartbeat may be sufficient until a permanent pacemaker can be implanted.

Perspective and Prospects

Over the years, huge advances have been made in resuscitation measures. More lives have been saved by the training of medical personnel to administer advanced life support before a patient reaches the hospital. Lifesaving drugs and defibrillation have greatly decreased the death rate for
heart attack victims and cardiac patients. With the continued training of emergency medical technicians, the survival rate can improve as a result of earlier and more aggressive medical treatment.

Medical treatment could be avoided entirely, however, if more preventive health measures were implemented. With continued research identifying risk factors, the public can be educated about how to prevent conditions that lead to heart attacks. Among the known risk factors are cigarette smoking, hypertension (high blood pressure), high cholesterol and triglycerides, lack of exercise, excess weight and improper nutrition, stress, and diabetes mellitus. Three risk factors cannot be changed: predisposing heredity, gender (men are more likely to have heart attacks), and increasing age.

With further research, the first group of risk factors may be addressed in society through extensive education, but heart attack rates cannot be curbed unless people change their lifestyles. An understanding of heredity, gender, and age risk factors can bring changes in these rates only through further research into their relationship to heart attacks.

Until people are willing to change their lifestyles, early recognition of the warning signs of a heart attack may be the easiest method of increasing survival rates. A heart attack occurs when the heart muscle itself does not receive enough oxygen. The heart muscle has its own blood supply through the coronary arteries. The blood supply to the heart may be reduced by a clot or by a narrowing in the coronary arteries. The warning signals of a heart attack include a squeezing tightness or pressure in the chest; pain in either arm, neck, jaw, or between the shoulder blades; sweating; nausea; weakness; and shortness of breath. People with diabetes and women may have milder or different symptoms. Too often, people deny that they could be suffering a heart attack, with many believing that the pain is heartburn or indigestion. If medical attention is sought immediately, however, severe damage can often be reduced or stopped. Special drugs such as streptokinase or tissue plasminogen activator (TPA) can dissolve clots that interfere with blood flow, while surgical techniques such as coronary artery bypass surgery (CABG) or angioplasty can open clogged arteries. Heart transplants offer a solution for patients with extensive heart damage. Research continues to decrease the rejection rates for heart transplants. Medications are being developed to decrease the buildup of plaque in arteries. The fields of genetics and gene therapy hold many keys to the prevention and treatment of heart disease.

It is important to note that all medically trained personnel, from the EMT to the emergency medicine physician, must be able to perform life-support measures. Unless patients have given appropriate do-not-resuscitate (DNR) orders, they will receive some form of the previously mentioned procedures. A living will
is a legal document that directs medical personnel in the level of care an individual wishes to have. For example, a person with advanced cancer may want to not be placed on a breathing machine. Those wishes are to be communicated through a living will. Without this document, health care providers are mandated by law to provide lifesaving measures. Future resuscitation measures will be influenced by ethical questions regarding when to sustain life.

Bystander CPR (initiation of CPR by the first person to find a cardiac arrest victim) is a vital component in the chain of survival between BLS and ACLS. It has been recognized, however, that very few people are willing to perform mouth-to-mouth rescue breathing, a vital component of success for CPR. Therefore, it has been acknowledged that it is better to at least open the victim’s airway by extending the neck and doing chest compressions alone versus doing nothing at all. The layperson will no longer be taught to check for a pulse before initiating CPR. Checking for a pulse was removed from the recommendations because it was demonstrated that laypersons could not be taught to reliably check for a pulse. Instead, they will be taught to look and examine for “signs of circulation,” which include breathing, coughing, or chest movements, before starting CPR. Another recommendation for BLS was to train nonmedical professionals such as police, firefighters, security officers, and others exposed to large populations in the use of the automated external defibrillator
(AED). The AED has two pads that, when applied to the chest of the cardiac
victim, analyze the electrical heart activity. The AED then administers the electrical shock (defibrillation) necessary to restart a heart if the cause of cardiac arrest was ventricular fibrillation, the most common arrhythmia of cardiac arrest. Bystander CPR and early defibrillation by the AED have been shown to do more to reduce morbidity and mortality from cardiac arrest than all current therapies for cardiac arrest combined.

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