COPD, or chronic obstructive pulmonary disease, is a condition in which the airways in the lungs become broken down and narrowed, often due to smoking cigarettes. Sometimes the air sacs are also damaged. As the lungs become more damaged over time, it becomes increasingly difficult to breathe through the narrowed airways (also known as bronchial tubes). When the damage is severe, it may also become difficult to get enough oxygen into the blood and to get rid of excess carbon dioxide. These changes all lead to shortness of breath and other symptoms. Unfortunately, the symptoms of COPD cannot be completely eliminated with treatment and the condition usually worsens over time.
The term COPD includes both chronic bronchitis and emphysema. The effects of chronic bronchitis and emphysema on breathing are similar, although there are some differences in symptoms, effects on the body, and treatment.
This article reviews the risk factors, symptoms, and tests used to diagnose COPD and its components, chronic bronchitis and emphysema. An article that discusses treatment of COPD is available separately. (See "Patient information: Chronic obstructive pulmonary disease (COPD) treatments (Beyond the Basics)".)
To understand why COPD develops, it is important to understand how the lungs work. Normally, air that we breathe passes from the nose and mouth through the airways to the tiny air sacs of the lung, called alveoli. In the air sacs, oxygen that we breathe passes through the walls of air sacs into the bloodstream (figure 1). Carbon dioxide passes in the reverse direction, out of the bloodstream, back into the alveoli, and is then eliminated by breathing out (figure 2). Carbon dioxide is a waste product of the body's metabolism, and must be regularly removed.
In people who develop COPD, irritating gases and particles are inhaled while smoking or breathing smoke filled air (secondhand smoke) or other fumes or particles, including air pollution. These gases and particles can injure the airways and lungs and cause irritation (inflammation). Over time, the inflammation becomes chronic, damages the lung tissue, and may cause scarring (figure 3). This lung damage makes it more difficult to breathe in and out and makes it harder for oxygen and carbon dioxide to pass across the walls of the air sacs. (See "Chronic obstructive pulmonary disease: Definition, clinical manifestations, diagnosis, and staging".)
Reasons for airflow blockage — Any disease that interferes with airflow out of the lungs can cause COPD. Most people with COPD have chronic bronchitis and emphysema, and some also have asthma.
Chronic bronchitis — Chronic bronchitis is the term used to describe people who have a chronic cough that produces sputum. Chronic bronchitis can scar the airways and reduce airflow.
Emphysema — Emphysema is the term used to describe damage to the air sacs in the lung. This damage can also restrict airflow.
Asthma — Asthma is a chronic inflammatory disorder of the airways. The chronic inflammation leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. Treatment is usually successful in reversing inflammation and airway narrowing. In a minority of people with asthma, the chronic inflammation permanently restricts airflow. When this airway narrowing cannot be completely reversed with treatment, the person is said to have COPD.
COPD RISK FACTORS
Smoking cigarettes significantly increases the risk of developing COPD. However, approximately 20 percent of people who develop COPD have never smoked.
Other factors that increase the risk of developing COPD include an abnormal sensitivity and exaggerated response to inhaled substances (called airway responsiveness), other exposures, such as secondhand exposure to smoke and workplace exposure to environmental dust or organic materials, or exposure to air pollution. COPD can run in families. (See "Chronic obstructive pulmonary disease: Risk factors and risk reduction".)
Genetic risk factors for COPD include severe deficiency of alpha-1 antitrypsin, a protein that protects the lungs. (See 'Alpha-1 antitrypsin deficiency' below.)
COPD usually causes no or mild symptoms at first. As the disease progresses, symptoms usually worsen. The most common symptoms include:
●Coughing and spitting up phlegm (mucus)
●Wheezing (a whistling or squeaking noise as you breathe)
●Shortness of breath at first with activity and, as disease worsens, at rest
If you have shortness of breath, a chronic cough, or cough up phlegm, your healthcare provider may recommend testing for COPD. The test used to diagnose COPD is a type of a pulmonary (lung) function test (PFT). (See "Chronic obstructive pulmonary disease: Definition, clinical manifestations, diagnosis, and staging".)
Pulmonary function tests (PFTs) — The pulmonary function test (PFT) that measures airway obstruction is called spirometry, and is required to diagnose COPD. Spirometry can detect COPD even in people who do not yet have symptoms.
During spirometry, you take a deep breath in and then blow out as hard and as fast as you can into a tube connected to a machine called a spirometer. The spirometer measures how fast and how much air you can blow out of your lungs. If the measurement is abnormal, the next step is to repeat the test after you use a bronchodilator that you breathe from an inhaler (which should improve the measurement). In people with asthma, the test measurements usually return to normal, but in people with COPD, the test measurements may only partially improve.
After the diagnosis of COPD is confirmed, spirometry is repeated over time to monitor the status of the disease and the effectiveness of treatment.
In some cases, additional pulmonary function tests are performed. These tests include measurements of lung volume, oxygenation, carbon dioxide, gas exchange, and exercise performance. The results of these tests are used to evaluate for lung diseases other than COPD that may be contributing to shortness of breath and to guide treatment of COPD in specific cases.
●Measurements of lung volume are usually performed in a box that looks like an old fashioned phone booth. People with more severe COPD may have an increase in lung volume.
●Another machine can measure the ability of the lungs to transfer gases like oxygen. This machine usually uses a very small amount of carbon monoxide, which is not enough to cause harm, but which reflects how oxygen is absorbed. With emphysema, the ability to transfer gases is typically reduced.
●Oximetry measures the amount of oxygen in the blood using a device called a finger oximeter, which clips onto the finger like a clip-on earring. Oximetry may also be checked during exercise, such as walking on level ground or climbing stairs. When the oxygen saturation drops to 88 percent or below, supplemental oxygen is usually prescribed. (See "Patient information: Chronic obstructive pulmonary disease (COPD) treatments (Beyond the Basics)".)
●An arterial blood gas sample may be obtained to determine if you have problems clearing carbon dioxide from the blood. Arterial blood gas is usually obtained by taking a blood sample from the artery in your wrist.
●There are several types of exercise tests. The simplest is to determine how far you can walk in 6 minutes. In this test, your pulse, difficulty breathing, and blood oximetry are usually measured. A more extensive test can be performed on a bicycle or a treadmill that can measure your maximum ability to perform physical work and can monitor both heart and lung function. This test is often used to assess other causes for shortness of breath and before starting a rehabilitation program.
Alpha-1 antitrypsin deficiency — Alpha-1 antitrypsin deficiency is a genetic disorder which causes 2 to 3 percent of the cases of emphysema in the United States. All adults who have symptoms of COPD should be tested for alpha-1 antitrypsin deficiency. (See "Clinical manifestations, diagnosis, and natural history of alpha-1 antitrypsin deficiency" and "Treatment of alpha-1 antitrypsin deficiency".)
Chest x-ray and computed tomography (CT scan) — In general, a chest x-ray is not needed to make the diagnosis of COPD because COPD does not affect the chest x-ray unless the disease is very severe. Your doctor may perform a chest x-ray, however, to exclude other lung diseases. The CT scan is a very sensitive test to detect the presence of emphysema. In patients with severe disease, a CT scan to determine the presence of emphysema can help guide treatment.
The first and most important part of any treatment plan for COPD is for smokers to stop smoking. This is true regardless of how long ago you were diagnosed with COPD and how severe your disease is. Studies of people with COPD show that worsening of the disease is slowed in people who stop smoking. (See "Patient information: Quitting smoking (Beyond the Basics)".)
Currently, there is no cure for COPD; however, many treatments are available for the symptoms and complications of this disorder. Most patients require ongoing treatment to keep symptoms under control.
A separate topic discusses the treatment of COPD. (See "Patient information: Chronic obstructive pulmonary disease (COPD) treatments (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Chronic obstructive pulmonary disease (COPD), including emphysema (The Basics)
Patient information: Shortness of breath (dyspnea) (The Basics)
Patient information: Pneumothorax (collapsed lung) (The Basics)
Patient information: Cough in adults (The Basics)
Patient information: Chronic bronchitis (The Basics)
Patient information: Atelectasis (The Basics)
Patient information: Chronic pulmonary aspergillosis (The Basics)
Patient information: Breathing tests (The Basics)
Patient information: Medicines for chronic obstructive pulmonary disease (COPD) (The Basics)
Patient information: Lung transplant (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Chronic obstructive pulmonary disease (COPD) treatments (Beyond the Basics)
Patient information: Quitting smoking (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Arrhythmias in COPD
Bullectomy for giant bullae in COPD
Chronic obstructive pulmonary disease: Definition, clinical manifestations, diagnosis, and staging
Chronic obstructive pulmonary disease: Risk factors and risk reduction
Delivery of inhaled medication in adults
Management of infection in acute exacerbations of chronic obstructive pulmonary disease
Dynamic hyperinflation in patients with COPD
Lung volume reduction surgery in COPD
Management of acute exacerbations of chronic obstructive pulmonary disease
Management of stable chronic obstructive pulmonary disease
Management of the patient with severe COPD and cardiovascular disease
Mechanical ventilation in acute respiratory failure complicating COPD
Chronic obstructive pulmonary disease: Prognostic factors and comorbid conditions
Nocturnal ventilatory support in COPD
Nutritional support in advanced lung disease
Oxygen conserving devices
Pulmonary rehabilitation in COPD
Role of anticholinergic therapy in COPD
Role of inhaled glucocorticoid therapy in stable COPD
Role of methylxanthines in the treatment of COPD
Role of mucoactive agents in the treatment of COPD
Role of systemic glucocorticoid therapy in COPD
Use of oxygen in patients with hypercapnia
Clinical manifestations, diagnosis, and natural history of alpha-1 antitrypsin deficiency
Treatment of alpha-1 antitrypsin deficiency
The following organizations also provide reliable health information.
●National Library of Medicine
(www.nlm.nih.gov/medlineplus/copdchronicobstructivepulmonarydisease.html, available in Spanish)
●National Heart, Lung, and Blood Institute
●American Lung Association
Patient Support — There are a number of online forums where patients can find information and support from other people with similar conditions.
●About.com COPD Forum