What Is Chronic Obstructive Pulmonary Disease?
Chronic obstructive pulmonary disease (COPD) is a lung disease that results in progressively impaired breathing. Two primary disorders that constitute COPD are emphysema and chronic bronchitis; most patients with COPD exhibit a combination of both.
Chronic bronchitis is a persistent inflammation of the bronchial tubes in the lungs, producing a recurrent cough with large amounts of mucus. When the cells lining the airways are irritated beyond a certain point, the tiny cilia (hair-like projections) that normally trap and eliminate foreign matter cease to function properly. The buildup of irritants leads to the production of excess mucus, which clogs air passages and produces the characteristic heavy cough of bronchitis. Bronchitis is classified as chronic when the patient coughs up sputum most of the days of a three-month period, two consecutive years in a row.
Emphysema is progressive damage to the lungs, resulting from destruction of tissue and loss of elasticity in the alveoli, where oxygen enters and carbon dioxide exits the bloodstream. If the lungs are damaged by the chemicals in cigarette smoke or by the persistent inflammation and coughing of chronic bronchitis, the delicate walls of the alveoli may become progressively enlarged, inelastic, and far less functional. The loss of elasticity, often combined with narrowing of the small airways in the lungs (sometimes to the point of collapse), traps stale air instead of allowing it to be exhaled. The affected air sacs are thus unable to deliver oxygen to the bloodstream or to remove carbon dioxide—contributing to the characteristic shortness of breath of emphysema.
Lung damage may progress until breathing is severely impaired, at which time the condition is potentially life-threatening. Low blood-oxygen levels may cause the pressure in the pulmonary arteries to become elevated (pulmonary hypertension), which in turn may prevent the right side of the heart from adequately pumping blood through the lungs.
The onset of COPD is usually very gradual. It develops over a number of years, and symptoms may not appear until the disease has already progressed quite far. Lung damage is permanent, but it is preventable in many cases by avoiding smoking.
Who Gets Chronic Obstructive Pulmonary Disease?
In the United States, approximately 16.4 million people suffer from COPD. The disease is two to three times more common in men than in women. Most people with COPD are current or former smokers.
- Shortness of breath, worse with exertion.
- A persistent, mucus-producing cough, especially in the morning (a symptom of chronic bronchitis).
- A chronic dry cough (a symptom of emphysema).
- In severe cases, symptoms of COPD may include coughing up blood, chest pain, and blue-purple complexion.
- Swollen legs and ankles (from cor pulmonale, or pulmonary hypertension and right-sided heart failure).
- Difficulty in exhaling.
- Smoking is the most common cause of COPD.
- Air pollution may be a contributing factor.
- Industrial or chemical fumes can damage the airways.
- Repeated viral or bacterial lung infections may thicken the lining of the bronchial walls, narrow the airways, and stimulate excessive mucus production in the lungs.
- People with occupations that require constant exposure to dust, chemicals, or other lung irritants, may be more susceptible to emphysema.
- Young children living with heavy smokers are more susceptible to chronic respiratory inflammation.
- Asthma also increases the risk for developing COPD later in life.
- A small number of people (an estimated 100,000 Americans) have a hereditary deficiency of an enzyme, alpha-1- antitrypsin, that in healthy people helps protect the lungs. In the absence of the enzyme, the walls of the alveoli break down, causing emphysema to develop. It is critical that people with this deficiency never smoke, since smoking significantly increases the severity of their emphysema.
After medical history and physical examination, pulmonary function tests are the primary diagnostic tools for COPD. Diagnosis may also include analysis of sputum and a blood sample from both an artery and a vein to measure oxygen and carbon dioxide levels.
Pulmonary function tests demonstrate characteristic abnormalities in lung function that, in the proper clinical context (i.e., medical history, physical examination, chest x-ray) confirm or support the diagnosis of COPD and give some idea of the degree of impairment and prognosis.
There are four components to pulmonary function testing:
- Spirometry. A spirometry machine measures the amount of air entering and leaving the lungs. The patient inhales into a tube as deeply as possible and then exhales as forcefully and rapidly as they can, until they can exhale no more. To be an adequate test, the patient must exhale all the air they possibly can continue exhaling for at least another 6 seconds. Usually, three separate attempts are made and the best result is used for evaluation.
- Postbronchodilator spirometry. Spirometry is often repeated after giving the patient a bronchodilator, such as an inhaled beta-agonist. This procedure provides some information on the potential responsiveness of the airways to medication. It is also useful for determining whether steroid treatment has been beneficial, a few weeks after initiating therapy.
Peak expiratory flow rate (PEFR) also can be obtained. PEFR can be compared with readings the patient obtains at home with a peak flow meter. A peak flow meter is a portable device that consists of a small tube with a gauge that measures the maximum force with which one blows air through the tube.
- Lung volumes. Lung volumes are measured in two ways, gas dilution or body plethysmography. The gas dilution method is performed after the patient inhales a gas, such as nitrogen or helium. The amount of volume in which the gas is distributed is used to calculate the volume of air the lungs can hold. Body plethysmography requires the patient to sit in an airtight chamber (usually transparent to prevent claustrophobia) and inhale and exhale into a tube. The pressure changes in the plethysmograph are used to calculate the volumes of air in the lungs.
The most important measurements obtained are residual volume and total lung capacity (TLC). A high TLC demonstrates hyperinflation of the lungs, which is consistent with emphysema. Increased residual volume signifies air trapping. This demonstrates an obstruction to exhalation.
- Diffusion capacity. Diffusion capacity is a measurement of gases transferred from the alveoli to the capillary. The patient inhales a very small amount (very safe) of carbon monoxide. How much of it is taken into the blood is measured. A reduced diffusion capacity is consistent with emphysema but is seen in a many other lung diseases as well.
- Don’t smoke; avoid smoke-filled rooms. Once a patient quits smoking, the rate of decline of lung function slows considerably.
- Drink plenty of fluids to loosen mucus secretions. Avoid caffeine and alcohol, however, since they have a diuretic effect and may lead to dehydration.
- Moisten indoor air with a cool-mist humidifier.
- Try to avoid going outside on cold days or days when the air quality is poor, and avoid exposure to cold, wet weather. If bronchitis is advanced and unrelenting, you may want to consider moving to a warmer and drier climate.
- Don’t use cough suppressants. Coughing is necessary to clear accumulated mucus from the lungs, and suppressing it may potentially lead to serious complications.
- A viral respiratory tract infection may trigger a flare-up of symptoms; decrease the risk of catching one by minimizing contact with people suffering from respiratory infections and washing your hands often. Get vaccinated for influenza (annually) and pneumonia (currently two different pneumonia vaccines are recommended).
- A bronchodilator may be prescribed to widen the bronchial passages. Oxygen may be administered in more severe cases. Some studies suggest that using a mucus clearance device before an inhaled bronchodilator can improve both lung function and exercise capacity while reducing shortness of breath. If bronchodilators fail to relieve airway obstruction adequately, corticosteroids (both oral and inhaled) may diminish inflammation in some people.
- Your doctor may prescribe antibiotics to treat or to prevent bacterial lung infections, since patients with COPD are more susceptible to these. Antibiotics should be taken for the full term prescribed.
- Your doctor may instruct you on how to drain mucus from your lungs by assuming various positions that lower your head below your torso (a technique known as postural drainage).
- Breathing exercises (as instructed by your doctor) may prove beneficial.
- In very severe cases of emphysema with extensive lung damage, a lung transplant may be advised (heart-and-lung transplants are advised if progressive lung disease has weakened the heart). In lung volume reduction surgery (LVRS), the upper portions of the diseased lungs are removed. How the procedure improves symptoms and lung function for some patients is not well understood. Single or double lung transplantation may be an option for some severe cases. Many selection criteria have to be met and they vary from facility to facility.
- Don’t smoke (smoking is the primary cause of COPD).
- Avoid spending long periods outside on days when the air quality is poor.
When To Call Your Doctor
- Call a doctor if symptoms become severe; for example, if shortness of breath or chest pain becomes more intense, your cough worsens or you cough up blood, you develop a fever, you begin to vomit, or your legs and ankles swell more than usual.
- Make an appointment with a doctor if you have experienced a recurrent, persistent, mucus-producing cough for parts of the last two years, or if you experience persistent shortness of breath.
- If you have sudden, severe difficulty breathing—and especially if your lips or complexion turn bluish or purplish—get medical assistance immediately.
Reviewed by Allen J. Blaivas, D.O., Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network.