Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the collective name for two diseases—emphysema and chronic bronchitis. Both diseases decrease air movement in the lungs because of blockage in the airways. Unlike asthma, in which the blockage comes and goes, in COPD, the blockage persists.

See the figure How Airways Become Obstructed.

Emphysema is the form of COPD in which abnormal air-filled spaces form among the millions of tiny air sacs (alveoli) in the lungs. These air-filled spaces develop when the thin walls that make up and separate clusters of alveoli and that hold the airways open are destroyed. Destruction of these walls leads to partial or complete obstruction of the small airways. The obstruction makes it difficult for air to move out of the lungs when a person exhales. Some air is trapped so that more air remains in the lungs after exhaling than would in a person with healthy lungs.

The number of tiny blood vessels (capillaries) in the walls of the alveoli decreases. Having fewer blood vessels and obstructed airways means that movement of oxygen and carbon dioxide between the alveoli and the blood is impaired. As a result, the level of oxygen in the blood may decrease while the level of carbon dioxide may increase. A lower oxygen level in the blood, if severe enough, causes shortness of breath, high blood pressure in the lungs, and strain on the right side of the heart. The strain can eventually lead to heart failure. A low oxygen level in the blood may also stimulate the body to produce more red blood cells, a condition called secondary polycythemia.

Chronic bronchitis is the form of COPD that affects the airways rather than the alveoli. Chronic bronchitis is characterized by a persistent cough that produces sputum. Chronic bronchitis differs from acute bronchitis, which usually begins with an infection and typically lasts no more than a few weeks; chronic bronchitis lasts 3 months or more during 2 successive years. Obstruction in chronic bronchitis is caused by swelling of the walls of the airways, spasm of muscle tissue in the walls of the airways, and formation of excess mucus, which is coughed up as sputum.

In the United States, about 16 million people have COPD. COPD is especially common among people over age 55. It is a very common cause of death and is becoming increasingly so. Fortunately, treatment can help control symptoms and improve the quality of life of most people with this disease.

Causes

Cigarette smoking is the most common cause of COPD. Almost all people with COPD are or have been smokers. Pipe and cigar smokers are at lower risk than cigarette smokers but are still at greater risk of COPD than are people who do not smoke tobacco in any form.

People exposed to smoke from nearby cigarette smokers (secondhand, or passive, smoke exposure) and people who have worked or lived in an environment polluted by chemical fumes or dust are also at a slightly increased risk of developing mild COPD. Thus, some nonsmokers develop mild COPD.

Symptoms

A mild cough that produces clear sputum is frequently an early symptom of COPD. The person usually has this cough when first getting out of bed in the morning. Gradually, shortness of breath develops as the obstruction slows airflow and increases the effort of breathing. At first, the shortness of breath may be noted only with physical exertion. Or, the shortness of breath may be noted only with a chest cold (acute bronchitis).

As the disease progresses, shortness of breath with exertion becomes more troublesome. The person may hear himself wheeze. Severe shortness of breath may even occur at rest. Shortness of breath while performing everyday activities, such as going to the bathroom, washing, and dressing, may persist after recovery from even a minor cold. More serious infections, such as pneumonia, become more common and cause symptoms more severe than in people with healthy lungs.

When COPD becomes more severe, some people lose weight because, among other reasons, shortness of breath makes eating difficult, and the overworked breathing muscles consume more energy. Commonly, the legs swell, which may be due to heart failure. People with more severe COPD may intermittently cough up blood even when they have mild lung infections. Coughing up blood also raises concern about the possibility of lung cancer, which occurs more frequently among people with smoking-related COPD. Headaches may occur in the morning because breathing worsens during sleep, which can lead to higher levels of carbon dioxide in the blood and decreased delivery of oxygen to the brain.

As COPD progresses, some people, especially those who have emphysema, develop altered breathing patterns. Some breathe out through pursed lips. Others are more comfortable standing over a table with their arms outstretched and their weight on their palms, a position that helps them breathe more easily. Some people gradually develop a barrel-shaped chest as their lungs expand because of trapped air. The skin, fingernails, or lips may turn bluish (cyanosis) if the level of oxygen in the blood is very low.

Occasionally, sudden pain develops on one side of the chest and shortness of breath worsens if an overexpanded area of the lung tears the lung's surface. The tear allows air to leak from the lung into the space between the lung and the rib cage (pleural space). This condition is called a pneumothorax. A pneumothorax can make breathing very difficult and usually requires emergency care.

Many people experience flare-ups, with a noticeable worsening of their cough, an increase in the amount of sputum, and increased shortness of breath. These flare-ups may be due to a viral infection, a bacterial infection, or exposure to inhaled substances that irritate the airways. During a flare-up, sputum color tends to change from white to yellow or green, and fever and body aches may occur. Shortness of breath may worsen, becoming a problem even when the person is at rest.

Diagnosis

Emphysema is diagnosed on the basis of the medical history and physical examination as well as on tests that measure lung function during inhalation and exhalation (pulmonary function tests). The doctor tries to determine, by measuring lung function, the severity of airflow obstruction and whether airflow improves in response to drugs. Chronic bronchitis is diagnosed solely on the basis of a history of a persistent cough that produces sputum.

When COPD is in an early stage, the doctor may find nothing during a physical examination. As the disease progresses, the doctor may hear wheezing through a stethoscope and may notice that exhalation takes longer than expected. The doctor may also notice that as the person breathes, the chest moves less and the muscles in the neck and shoulders contract. With severe disease, it may be difficult for the doctor to hear breath sounds at all with the stethoscope because less air is moving in and out of the air spaces and there is less lung tissue to transmit breath sounds to the chest wall.

In early COPD, results of a chest x-ray are usually normal. As COPD worsens, the chest x-ray shows over-expansion of the lungs.

Oxygen in the blood can be measured by taking a sample of blood from an artery or by using a clip attached briefly to an ear or a finger (pulse oximetry). Oxygen is often at low levels at rest or with exercise. Occasionally, a blood test shows an abnormally high number of red blood cells (polycythemia). Increasing the production of red blood cells is one way the body tries to overcome a decreased level of oxygen in the blood. When COPD is severe, high levels of carbon dioxide can be detected in blood samples taken from arteries.

Treatment

The most important treatment for COPD is to stop all forms of smoking, including cigarettes, cigars, and pipes. Ex-smokers should avoid inhaling secondary smoke, which may mean avoiding bars and restaurants that allow smoking or asking a family member who smokes to do so only outside the house. Stopping smoking when obstruction of airflow is minimal or even moderate often lessens cough, reduces the amount of sputum produced, and slows the progression of shortness of breath. Stopping smoking at any point can be beneficial. Reducing exposure to other irritants in the air, including secondhand smoke and air pollution, is also recommended. Many people with COPD benefit from staying in air-conditioned spaces.

If the person develops the flu (influenza) or pneumonia, the shortness of breath that accompanies COPD usually worsens suddenly. Therefore, people with COPD are advised to receive the influenza vaccine every year and the pneumococcal vaccine at the time of diagnosis. Revaccination with the pneumococcal vaccine is often recommended every 6 years. At the first sign of a cold, a person with COPD should consult a doctor. Often, the doctor provides a plan for such occasions so that the patient can begin treatment on his own.

Treatment of symptoms: Treatment aims to relieve symptoms of wheezing and shortness of breath by reducing airflow obstruction. Obstruction due to emphysema is irreversible, so treatment is not very helpful for the emphysema component of COPD. But other changes in the airways of people with COPD are to some degree potentially reversible, including muscle spasm and increased mucus and swelling of the walls of the airways. Therefore, treatment that targets these components can be helpful in reducing airflow obstruction.

Many drugs used to treat COPD are taken through an inhaler, which is a device that allows the user to spray very tiny droplets of a drug into the lungs via the mouth and throat. These droplets can then be inhaled deeply into the lungs. An inhaler that provides a specific and consistent dose is called a metered-dose inhaler. Ipratropium, which helps open (dilate) obstructed airways by reducing muscle spasm, can be taken up to 4 times daily. A short-acting beta-adrenergic agonist drug, such as albuterol, relieves shortness of breath more rapidly. A combination of ipratropium and albuterol, taken through an inhaler, is also available.

See the figure How to Use a Metered-Dose Inhaler.

Salmeterol, a long-acting beta-adrenergic agonist drug, is taken every 12 hours with a small disc-shaped device that contains the drug in powder form. After pulling a small lever on the device, the person places his mouth around a small opening and inhales the salmeterol in a single breath. Salmeterol provides prolonged relief of symptoms for some people, especially at night, but does not begin working for at least 15 minutes after use.

For people who have difficulty using metered-dose inhalers or who do not get enough relief from them, other options are available. A delivery device called a spacer can be used with a metered-dose inhaler. Ipratropium and albuterol may also be taken with the aid of a nebulizer. A nebulizer is a portable machine that creates a mist of drug, and its use does not have to be coordinated with breathing. It requires a power source, such as household current, a battery, or a car's cigarette lighter. Therapy with a nebulizer is reserved for people who have severe disease.

Theophylline is often taken by people who respond minimally or not at all to other drugs. This drug is taken in pill form. The dose is adjusted by the doctor based on levels of theophylline in the blood, which are measured periodically. The short-acting form is usually taken 4 times a day, but long-acting forms of theophylline can be taken once or twice daily.

Corticosteroids may be helpful for people whose symptoms cannot be controlled by the other drugs. Corticosteroids lessen symptoms and help reduce the frequency of flare-ups. Corticosteroids are available in inhalers or as pills. Recently, a combination of salmeterol and a corticosteroid in powder form has been developed. This combination of drugs is taken with a disc-shaped device. After pulling the small lever on the device, the person places his mouth around a small opening and inhales both drugs in a single breath.

Because inhaled corticosteroids go directly into the lungs, they produce fewer side effects than corticosteroids taken as pills. However, high doses of inhaled corticosteroids taken for several years may also have side effects, such as osteoporosis. Corticosteroids taken as pills are largely restricted to people with COPD flare-ups or those who have severe symptoms from airflow obstruction despite undergoing other therapy.

No reliable therapy is available to thin the mucus so that it can be coughed up more easily. However, drinking enough to avoid dehydration may prevent thick mucus accumulation. When COPD is severe and mucus is excessive, respiratory therapy may help loosen mucus in the chest.

Treatment of flare-ups: A doctor treats flare-ups as soon as possible. About half of flare-ups are due to viruses and half to bacterial infections.

If a viral cause is suspected, the doctor usually recommends rest, plenty of fluids, and, occasionally, corticosteroids for several days. If treatment fails, hospitalization may be needed.

If a bacterial infection is suspected, the doctor usually prescribes an antibiotic. Many doctors give people who have moderate or severe COPD a supply of an antibiotic and advise them to start taking the drug early in a flare-up. There are many options for antibiotics that can be taken by mouth. Antibiotics do not prevent flare-ups. Sometimes corticosteroids are taken by mouth for about 10 to 14 days to help reduce the severity and length of flare-ups due to bacterial infections.

Oxygen therapy: Oxygen therapy prolongs life and improves quality of life for people with severe COPD and severely reduced oxygen levels in their blood. Although round-the-clock therapy is best, using oxygen at least 12 hours a day also has some benefits. This therapy often improves mental functioning and helps relieve shortness of breath, high blood pressure in the lungs, and heart failure caused by COPD.

Different devices are available for providing oxygen therapy. People who are homebound can use electrically powered oxygen concentrators. The use of compressed oxygen in small tanks permits trips outside the home. Liquid oxygen systems are more expensive but are preferable for active people, because liquid oxygen permits longer trips away from home. A special valve called a demand valve can be attached to the portable oxygen delivery device to increase the length of time that the unit can be used before a refill is needed. Oxygen therapy cannot be used near open flames or while smoking.

Surgery: Lung volume reduction surgery, which involves removing areas where air is persistently trapped, may help relieve severe symptoms.

Pulmonary rehabilitation: Pulmonary rehabilitation can help most people feel better. Programs include education about the disease, exercise, nutrition, and counseling. These programs can improve the person's 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 the clinic and at home. Stationary bicycling, stair climbing, and walking are used to exercise the legs. Weight lifting is used for the arms. Often, oxygen is used during exercise. However, gains are quickly lost if the person stops exercising. Special techniques are taught for decreasing shortness of breath during such strenuous activities as exercise and sexual activity. For example, the person can be taught to keep his lips partly closed, as if whistling, during exhalation (pursed-lip breathing). Pulmonary rehabilitation, however, does not improve lung function or prolong survival.

Outlook

As airway obstruction worsens, the outlook becomes progressively worse, with an increased risk of death. Death may result from respiratory failure, pneumonia, pneumothorax, heart rhythm abnormalities (arrhythmias), or blockage of the arteries that lead to the lungs (pulmonary embolism). Cigarette smokers lose lung function more rapidly than nonsmokers do. If a person stops smoking, lung function improves minimally. Continued smoking, however, virtually ensures that symptoms will worsen. People with COPD have a risk of lung cancer beyond that due to their use of cigarettes.

People in late stages of COPD are likely to need considerable help adhering to their recommended medical care and with performing everyday activities. Some older people find that staying at home becomes too difficult because of fatigue, shortness of breath, the need for oxygen, and the complexities of taking prescribed drugs. Such people may move to a nursing home to obtain the care they need.

People with end-stage disease who develop flare-ups or pneumonia may need to have a tube put down their throat and be temporarily supported with mechanical ventilation in an intensive care unit. The period of mechanical ventilation may be short or long, and some people remain dependent on the ventilator until death. People on a ventilator cannot eat or talk, thus quality of life is greatly diminished. It is important for people to consider and discuss with their doctors and loved ones whether they wish to have this kind of therapy. Some people choose another alternative—hospice care. The best way of ensuring that one's wishes are carried out is to discuss them with loved ones and to have completed an advance directive, such as a living will or a durable power of attorney for health care.