Table of Contents
Definition of Chronic Obstructive Pulmonary Disease (COPD)
Chronic obstructive pulmonary disease are a serious, often debilitating, and potentially fatal condition in which INFLAMMATION and scarring destroy alveoli, bronchioles, and bronchi.
The most common cause of COPD is cigarette smoking; 8 of 10 Americans who have COPD are smokers. Uncontrolled ASTHMA and chronic lung diseases such as ASBESTOSIS and SILICOSIS can also progress to COPD. About 16 million people in the United States have COPD and more than 100,000 of them die from it each year.
COPD takes years to decades to develop, and its damage is permanent. The most common presentation is that of chronic BRONCHITIS, in which there is repeated inflammation of the bronchi. Each bout of inflammation results in the formation of SCAR tissue as the damaged area heals. Over time the scar tissue causes the bronchi to narrow, with areas of constriction that severely limit the flow of air. ATELECTASIS (collapse) may occur in affected bronchial structures, reducing the ability of the lung to diffuse oxygen into the bloodstream.
In about 10 percent of people who have COPD the damage extends to the alveoli, the clusters of air sacs where oxygen-carbon dioxide exchange takes place. Repeated inflammation and scarring causes the alveoli to enlarge and lose elasticity, a state called emphysema. The damaged alveoli can take in air but cannot collapse sufficiently to expel the air completely. A rare form of emphysema is an inherited deficiency of the enzyme alpha-1-antitrypsin (AAT), which regulates the presence of elastin in the tissues of the alveoli. AAT deficiency results in reduced elastin, further limiting alveolar function. Because of the intimate correspondence between the capillary BLOOD supply and alveolar oxygen content, blood supply shifts away from damaged alveoli.
The ultimate damage of COPD, regardless of whether the primary course of disease started as bronchial or alveolar, is so profound that both dimensions of damage eventually overtake the LUNGS and the lungs lose the ability to recoil (return to their normal shape and size), diminishing the ability to exhale. Consequently, people who have COPD can breathe in with relative ease but struggle to move air back out of their lungs. People who have moderate to advanced COPD typically exhale through pursed lips, an effort to more forcefully exhale. Even with this effort, the person may be unable to blow out a match.
As the disease process progresses the less elastic lungs expand within the thoracic cavity, pushing the ribs out and the DIAPHRAGM down to produce a characteristic barrel chest deformity. However, these structural changes further limit the ability of the diaphragm and intercostal muscles to expand the chest for inhalation, restricting the ability of the lungs to draw in air. This generates a characteristic posture adaptation in which the person leans forward to use other muscles in the neck and shoulders to assist with BREATHING. Ordinary movements such as raising the arms (such as to wash or brush the hair) consequently cause shortness of breath because such movements reduce the involvement of these ancillary muscles. In its later stages COPD affects both inhalation and exhalation.
Symptoms and Diagnostic Path
The symptoms of COPD include
- progressive DYSPNEA (shortness of breath)
- wheezing (whistling sounds with exhalation)
- persistent, productive COUGH
- HEMOPTYSIS (bloody SPUTUM)
- edema (swelling due to fluid retention) in the feet, ankles, and lower legs
- CYANOSIS (bluish hue to the lips and SKIN that signals inadequate oxygenation)
- physical signs characteristic of COPD (barrel chest, purse-lip breathing, forward-leaning posture) when emphysema is dominant
- current or previous cigarette smoking
The diagnostic path includes a complete pulmonary workup to evaluate lung capacity and function, which typically show significant reductions. Chest X-rays and COMPUTED TOMOGRAPHY (CT) SCAN show the extent of damage to the lungs as well as displacement of the thoracic structures. The doctor typically does sputum cultures to identify or rule out INFECTION. Diagnostic blood tests often show an elevated ERYTHROCYTE (red blood cell) count particularly in people who have low oxygen levels, indicative of the body’s attempt to improve the oxygen-carrying ability of the blood. Diagnostic efforts focus on ruling out other possible causes for symptoms as well as correlating physical findings with history of smoking.
Classification of Chronic Obstructive Pulmonary Disease (COPD)
|stage 0||at risk||smokes but has no COPD symptoms|
|stage 1||mild||chronic COUGH|
|stage 2||moderate||chronic, productive cough DYSPNEA with exertion|
|stage 3||severe||chronic, productive cough excessive SPUTUMdyspnea at rest right HEART FAILURE common|
Treatment Options and Outlook
The most important element of treatment is SMOKING CESSATION. Although it is not possible to reverse damage that has already occurred, treatment aims to minimize further lung damage and improve function of the remaining lung. Medications such as bronchodilators relax and open the airways, easing the flow of air in and out of the lungs. CORTICOSTEROID MEDICATIONS reduce inflammation and in some people may also help open the airways. When infection is present, the doctor may prescribe ANTIBIOTIC MEDICATIONS.
However, people who have COPD often have extensive bacterial flora, making it difficult for the doctor to determine whether there is an actual infection present. People who have COPD should receive annual INFLUENZA immunizations and PNEUMONIA vaccination every five years. As with all lung diseases, it is important to minimize as much as possible other triggers: SINUSITIS, GASTROESOPHAGEAL REFLUX DISORDER (GERD), and exposure to known ALLERGENS.
For some people surgery to remove the upper lobes of the lungs, called lung volume reduction surgery (LVRS), relieves tension within the thoracic cavity and improves pulmonary function and overall lung capacity. LUNG TRANSPLANTATION may be a viable treatment option for some people, replacing one of the diseased lungs with a donor lung. The criteria for these procedures are stringent and take into account numerous health and lifestyle factors.
Nutritional support is essential for people with advanced COPD, who typically lose significant body weight as the effort to breathe requires intense work from numerous muscles. Regular physical exercise is also important. Though breathing with exertion may severely limit the duration of activity, maintaining physical STRENGTH allows the body to make the most of the available oxygen the lungs can diffuse into the bloodstream. Many hospitals have pulmonary rehabilitation programs with specialists who can teach targeted exercises to improve AEROBIC FITNESS and MUSCLE strength. For many people pulmonary rehabilitation is as effective as any surgical alternatives. Walking remains one of the most effective activities.
Complications of COPD are common, particularly in the later stages. Typical complications include HEART FAILURE, PULMONARY HYPERTENSION and RESPIRATORY FAILURE. Doctors sometimes refer to the combination of right-heart failure and pulmonary hypertension as cor pulmonale. People who have COPD are particularly vulnerable to viral infections such as COLDS and influenza, and often develop secondary bacterial infections such as pneumonia and acute bronchitis.
Risk Factors and Preventive Measures
The leading risk factor for COPD is cigarette smoking. The most effective preventive measure is never to smoke and to avoid exposure to secondhand smoke (ENVIRONMENTAL CIGARETTE SMOKE). Smoking cessation can improve lung capacity and function, though cannot undo damage that has already occurred. Prompt and appropriate treatment of other pulmonary conditions, such as asthma, helps minimize permanent damage that could set the stage for COPD to subsequently develop. Though COPD occurs primarily in people over age 40, this is a consequence of cumulative damage to the lungs over time rather than aging.