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Chronic obstructive
pulmonary disease is persistent obstruction of the airways occurring with
emphysema, chronic bronchitis, or both disorders.
In the United States, about 12 million people suffer from chronic obstructive pulmonary disease (COPD). It is second only to heart disease as a cause of disability that forces people to stop working. It is the fourth most common cause of death, accounting for more than 120,000 deaths per year in the United States. The number of deaths from COPD has increased more than 60% over the last 20 years, and more than 95% of all COPD-related deaths occur in people older than age 55. COPD affects men more often than women, but men and women die as a result of COPD at about equal rates. COPD is more often fatal in whites than in nonwhites and in blue-collar workers than in white-collar workers.
COPD leads to chronic airflow obstruction, which is defined as a persistent decrease in the rate of airflow from the lungs when the person breathes out (exhales). This airflow obstruction is partially reversible in most people, either spontaneously or with treatment. COPD includes the diagnoses of chronic obstructive bronchitis and emphysema. Many people have both disorders. Chronic bronchitis is defined as cough that produces sputum repeatedly during two successive years. When chronic bronchitis involves airflow obstruction, it qualifies as chronic obstructive bronchitis. Emphysema is defined as widespread and irreversible destruction of the alveolar walls (the cells that support the air sacs, or alveoli, that make up the lungs) and enlargement of many of the alveoli.
The small airways (bronchioles) of the lungs contain smooth muscles and are normally held open by their attachments to alveolar walls. In emphysema, the destruction of alveolar wall attachments results in collapse of the bronchioles, causing permanent airflow obstruction. In chronic bronchitis, the glands lining the larger airways (bronchi) of the lungs enlarge and increase their secretion of mucus. Inflammation of the bronchioles develops and causes smooth muscle to contract (spasm), further obstructing airflow. Inflammation also causes airflow to be blocked by secretions. Asthma is also characterized by airflow obstruction (see Asthma). However, in contrast with the airflow obstruction of COPD, the airflow obstruction of asthma is completely reversible in most people, either spontaneously or with treatment.
The airflow obstruction of COPD causes air to become trapped in the lungs after a full exhalation, increasing the effort required to breathe. Also in COPD, the number of capillaries in the walls of the alveoli decreases. These abnormalities impair the exchange of oxygen and carbon dioxide between the alveoli and the blood. In the earlier stages of COPD, oxygen levels in the blood may be decreased, but carbon dioxide levels remain normal. In the later stages, carbon dioxide levels increase and oxygen levels fall.
The decrease in oxygen levels in the blood stimulates the bone marrow to send more red blood cells into the bloodstream, a condition known as secondary polycythemia (see Myeloproliferative Disorders: Polycythemia Vera). The decrease in oxygen levels in the blood also increases the pressure in the artery through which blood flows from the heart to the lungs (pulmonary artery). As a result of the increased pressure, pulmonary hypertension and cor pulmonale can occur (see Pulmonary Hypertension:Pulmonary Hypertension ). People with COPD also have an increased risk of developing heart rhythm abnormalities (arrhythmias). For smokers, the risk of developing lung cancer is higher than it would be on the basis of cigarette smoking alone.
Causes
Cigarette smoking is the most important cause of COPD, although only about 15% of smokers develop the disease. Pipe and cigar smokers develop COPD more often than nonsmokers but not as often as cigarette smokers. With aging, susceptible cigarette smokers lose lung function more rapidly than nonsmokers. Lung function improves only a little if people stop smoking. However, the rate of decline of lung function returns to that of nonsmokers when people stop smoking, thus delaying development and progression of symptoms.
COPD tends to occur more often in some families, so there may be an inherited tendency. Working in an environment polluted by chemical fumes or dust may increase the risk of COPD (see Environmental Lung Diseases: Introduction). Exposure to air pollution and to smoke from nearby cigarette smokers (secondhand or passive smoke exposure) worsens COPD and may cause COPD.
A rare cause of COPD is a hereditary condition in which the body produces a markedly decreased amount of the protein alpha1-antitrypsin. The main role of this protein is to prevent neutrophil elastase (an enzyme in certain white blood cells) from damaging the alveoli. Consequently, emphysema develops by early middle age in people with severe alpha1-antitrypsin deficiency (also called alpha1-antiprotease inhibitor deficiency), especially in those who also smoke.
Symptoms
In people with COPD, a mild cough that produces clear sputum develops by around age 45. The cough usually occurs when the person first gets out of bed in the morning. Cough and sputum production persist. Shortness of breath may occur with exertion. Sometimes, shortness of breath first occurs only with a lung infection, during which time the person coughs more and has an increased amount of sputum. The color of the sputum changes from clear or white to yellow or green.
By the time people with COPD reach their middle to late 60s, especially if they continue smoking, shortness of breath with exertion becomes more troublesome. Pneumonia and other lung infections occur more often. They may result in severe shortness of breath even when the person is at rest and may require hospitalization. Shortness of breath during activities of daily living, such as toileting, washing, dressing, and sexual activity, may persist after the person has recovered from the lung infection.
About one third of people with severe COPD experience severe weight loss, in part because shortness of breath makes eating difficult and in part because of increased levels in the blood of a substance called tumor necrosis factor. Swelling of the legs often develops, which may be due to cor pulmonale. People with COPD may intermittently cough up blood, which is usually due to inflammation of the bronchi, but which always raises the concern of lung cancer. Morning headaches may occur because breathing decreases during sleep, which causes increased retention of carbon dioxide.
As COPD progresses, some people, especially those who have emphysema, develop unusual breathing patterns. Some people breathe out through pursed lips. Others find it more comfortable to stand over a table with their arms outstretched and weight on their palms, a maneuver that improves the function of the respiratory muscles. Over time, many people develop a barrel chest as the size of the lungs increases because of trapped air. Low oxygen levels in the blood can give a blue tint to the skin (cyanosis). Clubbing of the fingers is rare (see Symptoms and Diagnosis of Lung Disorders: Clubbing) and raises the suspicion of lung cancer.
Fragile areas in the lungs may rupture, permitting air to leak from the lung into the pleural space, a condition called pneumothorax (see Pleural Disorders: Pneumothorax). This condition often causes sudden pain and shortness of breath and requires immediate intervention by a doctor to remove the air from the pleural space.
A flare-up of COPD is a worsening of symptoms, usually cough, increased sputum, and shortness of breath. Sputum color often changes to yellow or green, and fever and body aches sometimes occur. Shortness of breath may be present when the person is at rest and may be severe enough to require hospitalization. Severe air pollution, common allergens, and viral or bacterial infections may cause flare-ups. During severe flare-ups, people may develop a life-threatening condition called acute respiratory failure. Among the possible symptoms are severe shortness of breath (a feeling likened to being drowned), severe anxiety, sweating, cyanosis, and confusion.
Diagnosis
Chronic bronchitis is diagnosed by the history of a prolonged productive cough. People with chronic obstructive bronchitis have chronic bronchitis and evidence of airflow obstruction on pulmonary function tests. Emphysema is diagnosed on the basis of findings observed during a physical examination and on pulmonary function test results. However, by the time the doctor notices these abnormalities, emphysema is moderately severe. It is not important for doctors to differentiate between chronic obstructive bronchitis and emphysema. The most important determinant of how the person feels and functions is the severity of the airflow obstruction.
In mild COPD, a doctor may find nothing unusual during the physical examination. As the disease progresses, wheezes may be heard through the stethoscope, and prolonged expiration and decreased breath sounds become apparent. Chest movement diminishes during breathing, and use of the neck and shoulder muscles in breathing may occur.
In mild COPD, the chest x-ray is usually normal. As COPD worsens, the chest x-ray shows over-inflation of the lungs. Thinning of blood vessels suggests the presence of emphysema.
Doctors can evaluate airflow obstruction with forced expiratory spirometry (see Symptoms and Diagnosis of Lung Disorders: Lung Volume and Flow Rate Measurements). Decrease in the forced expiratory volume in 1 second (FEV1) and the ratio of the FEV1 to the forced vital capacity (FVC) are required to demonstrate airflow obstruction and to make the diagnosis.
A blood test may show an abnormally high level of red blood cells (polycythemia). Pulse oximetry or a sample of blood taken from an artery often shows low levels of oxygen. High levels of carbon dioxide in the arteries occur late in the course of the disease.
In people who develop COPD at a young age, especially when there is a family history of COPD, the alpha1-antitrypsin blood level is measured to determine whether alpha1-antitrypsin deficiency is present. This genetic disorder is also suspected when COPD develops in people who have never smoked.
Treatment
The most important treatment for COPD is to stop smoking (see Drug Use and Abuse: Nicotine). Stopping smoking when the airflow obstruction is mild or moderate often lessens cough, reduces the amount of sputum, and slows the development of shortness of breath. Stopping smoking at any point in the disease process provides some benefit. Trying several strategies at once is most likely to be effective. Among these strategies are committing to a specific date for quitting, using behavior modification techniques (for example, making cigarettes difficult to obtain or rewarding oneself for abstaining for increasingly long periods of time), group counseling and support sessions, and nicotine replacement (for example, by chewing nicotine gum, wearing a nicotine skin patch, or using a nicotine inhaler, nicotine lozenge, or nicotine nasal spray). The drugs varenicline and bupropion may also help decrease tobacco craving. However, even with the most effective methods, less than half of people have quit smoking after one year.
People should also try to avoid exposure to other airborne irritants, including secondhand smoke and air pollution.
Contracting influenza or developing pneumonia may worsen COPD markedly. Therefore, all people with COPD should receive an influenza vaccination every year and a pneumococcal vaccination every 5 or 6 years.
Treatment of Symptoms:
Wheezing and shortness of breath are relieved when airflow obstruction improves. Although airflow obstruction due to emphysema is not reversible, bronchial smooth muscle spasm, inflammation, and increased secretions are all potentially reversible.
Inhaled bronchodilators are given with a device that allows the user to spray a specific and consistent dose of a drug into the airways via the mouth and throat (metered-dose inhaler). Inhaled bronchodilators include anticholinergic and beta-adrenergic agonist drugs. Both relax muscles around the bronchioles. Anticholinergic drugs include ipratropium and tiotropium. Ipratropium is given about 4 times daily, and tiotropium is given once daily. Inhaled short-acting beta-adrenergic agonists, such as albuterol , more rapidly relieve shortness of breath than anticholinergic drugs and so can be most useful during flare-ups. Salmeterol , a long-acting beta-adrenergic agonist with a delayed onset of action, can be given by inhalation every 12 hours. This drug is useful for prolonged relief of symptoms in some people, especially at night.
Many people can use metered dose inhalers more effectively when they inhale the drug through a delivery device called a spacer (see Asthma: How to Use a Metered-Dose Inhaler ). Inhaled bronchodilators may also be given using nebulizers. This mode of therapy should be reserved for people who have severe disease or for those who cannot use a metered-dose inhaler properly. A nebulizer creates a mist of drug, and the timing of its inhalation does not have to be coordinated with breathing. Nebulizers are more portable than they were in the past; some units can even be plugged into the cigarette lighter in a car.
Corticosteroids are helpful for many people with moderate and severe COPD whose symptoms cannot be controlled by the other drugs or for those who get frequent flare-ups despite the use of other drugs. Inhaled corticosteroids do not prevent decline of lung function over time. However, their use improves symptoms and results in decreased frequency of COPD flare-ups. Because the drug is delivered to the lungs, inhaled corticosteroids produce fewer side effects than treatment given by mouth. However, high doses of inhaled corticosteroids can have effects throughout the body, such as worsening of osteoporosis. Corticosteroids given by mouth are largely restricted to treatment of COPD flare-ups or are given to people who continue to have symptoms from airflow obstruction and who are not responding to a simpler regimen.
Theophylline is given only to people who do not respond to other drugs. The dose must be carefully controlled by the doctor, and, in some patients, levels of the drug in the blood must be measured periodically. A long-acting form of the drug permits once-daily or twice-daily dosing in many people and helps to control shortness of breath at night.
There is no reliable therapy for thinning secretions so they can be coughed up more easily. However, avoiding dehydration may prevent thickening of secretions. A rule of thumb is to drink enough fluids to keep the urine pale except for that passed first in the morning. In severe COPD, respiratory therapy may help loosen secretions in the chest.
Spirometry and pulse oximetry are often used to monitor symptoms. Arterial blood gas measurements add information that is useful in severe disease.
Treatment of Flare-ups:
Flare-ups should be treated as soon as possible. When bacterial infection is suspected, a 7- to 10-day course of antibiotic treatment is usually prescribed. Many doctors give people who have COPD a supply of an antibiotic to be kept on hand and taken early in a flare-up. A number of antibiotics can be taken by mouth, including trimethoprim-sulfamethoxazole , doxycycline , amoxicillin -clavulanate, and ampicillin . Many doctors reserve more expensive antibiotics, such as azithromycin , clarithromycin , and levofloxacin , for more severe lung infections, for people in whom treatment with the older and less expensive drugs has not worked, for those who have severe symptoms, and for those at risk of infection with organisms that are not likely to be eliminated by the older drugs (resistant bacteria). People whose immune system is suppressed or those who live in nursing homes are most likely to be infected with resistant bacteria.
People with severe flare-ups require hospitalization and treatment with short-acting beta-adrenergic agonist drugs and ipratropium , oral or intravenous corticosteroids, and oxygen. They may require machine-assistance with breathing (mechanical ventilation) and sometimes placement of an endotracheal (breathing) tube. Although many people with COPD think they should take antibiotics to prevent flare-ups, there is no indication that this practice is effective.
Oxygen Therapy:
Long-term oxygen therapy (see Rehabilitation for Lung and Airway Disorders: Oxygen Therapy) prolongs the life of people who have advanced COPD and severely reduced oxygen levels in their blood. Although round-the-clock therapy is best, using oxygen 12 hours a day also has some benefits. This therapy reduces the excess of red blood cells caused by low blood oxygen levels and helps to relieve cor pulmonale caused by COPD. Oxygen therapy may also improve shortness of breath during exercise.
Different devices are available for oxygen therapy. Electrically driven oxygen concentrators are used when electrical outlets are available. Compressed oxygen is available in small tanks that permit people to travel outside of their homes for 2 to 6 hours. Liquid oxygen systems are more expensive but are preferable for active people as they permit several hours away from the source reservoir. People must never use oxygen therapy near open flames or while smoking.
Pulmonary Rehabilitation:
Pulmonary rehabilitation can help people who have COPD (see Rehabilitation for Lung and Airway Disorders: Introduction), but it does not improve lung function. Programs encompass education about the disease, exercise, and nutritional and psychosocial counseling. These programs can improve independence and quality of life, decrease the frequency and length of hospital stays, and improve the ability to exercise. Exercise programs can be carried out in an outpatient setting or at home. Walking (sometimes on a treadmill) is usually used to exercise the legs. Sometimes stationary bicycling and stair climbing are also used. Weight lifting is used for the arms. Often, oxygen is recommended during exercise. As with any exercise program, gains in conditioning are quickly lost if the person stops exercising. Special techniques are taught for decreasing shortness of breath during activities, such as cooking, engaging in hobbies, and sexual activity.
Other Treatments:
Over-the-counter cough suppressants usually help little and are not recommended. For people with a severe alpha1-antitrypsin deficiency, the missing protein can be replaced. The treatment, which requires weekly intravenous infusions of the protein, is expensive.
Single lung transplantation may be used in certain people who are usually younger than 60 and have severe airflow obstruction. The goal of lung transplantation is to improve quality of life, because survival time is rarely increased. Lifelong immunosuppression is required, placing people at risk of infections.
Lung volume reduction surgery can be carried out in people with severe emphysema in the upper portions of their lungs. In this operation, the most severely diseased portions of the lungs are removed, thus permitting the remaining portions of the lungs and the diaphragm to function better. It is not known how long the improvement lasts. People are required to stop smoking for at least 6 months before surgery. They should undergo an intense rehabilitation program to determine whether overall function can be improved significantly without surgery before undertaking this operation, which carries a risk of death of about 5%.
Prognosis
and End-of-Life Issues
COPD itself usually does not cause death or severe symptoms if the person stops smoking at a time when airflow is only mildly obstructed. Continued smoking, however, virtually assures that symptoms will worsen. With moderate and severe airflow obstruction, the prognosis becomes progressively worse. People in advanced stages of COPD are likely to need considerable help with medical care and with activities of daily living. They may, for example, arrange to live on a single floor of their house, eat several small meals rather than one large meal, and avoid wearing shoes that must be tied. Death may result from respiratory failure, lung cancer, heart disorders (for example, heart failure or heart rhythm abnormalities), pneumonia, pneumothorax, or blockage of the arteries leading to the lungs (pulmonary embolism).
People with end-stage disease who develop flare-ups may need a breathing tube and mechanical ventilation. The duration of mechanical ventilation may be prolonged, and some people remain ventilator-dependent until death. It is important for people to consider with their doctors and loved ones whether or not they wish this kind of supportive therapy and to do so before a flare-up occurs. The best way to ensure that the person's wishes regarding prolonged mechanical ventilation are carried out is to prepare an advance directive (see Legal and Ethical Issues: Advance Directives) and appoint a health care proxy (see Legal and Ethical Issues: Surrogate Decision Making).
Last full review/revision April 2007 by Robert A. Wise, MD
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