Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive lung disease, is a general term for a group of conditions in which there is persistent difficulty in expelling (or exhaling) air from the lungs. COPD commonly refers to two related, progressive diseases of the respiratory system, chronic bronchitis and emphysema. Because smoking is the major cause of both diseases, chronic bronchitis and emphysema often occur together in the samepatient.

COPD is one of the fastest-growing health problems. Nearly 16 million peoplein the United States, 14 million with chronic bronchitis and 2 million with emphysema, suffer from COPD. COPD is responsible for more than 96,000 deaths annually, making it the fourth leading cause of death. Although COPD is more common in men than women, the increase in incidence of smoking among women since World War II has produced an increase in deaths from COPD in women. COPD has a large economic impact on the health-care system and a destructive impacton the lives of patients and their families. Quality of life for a person with COPD decreases as the disease progresses.

In chronic bronchitis, chronic inflammation caused by cigarette smoking results in a narrowing of the openings in the bronchi, the large air tubes of therespiratory system, and interferes with the flow of air. Inflammation also causes the glands that line the bronchi to produce excessive amounts of mucus,further narrowing the airways and blocking airflow. The result is often a chronic cough that produces sputum (mainly mucus) and shortness of breath. Cigarette smoke also damages the cilia, small hairlike projections that move bacteria and foreign particles out of the lungs, increasing the risk of infections.

Emphysema is a disease in which cigarette smoke causes an overproduction of the enzyme elastase, one of the immune system's infection-fighting biochemicals. This results in irreversible destruction of a protein in the lung called elastin, which is important for maintaining the structure of the walls of thealveoli, the terminal small air sacs of the respiratory system. As the wallsof the alveoli rupture, the number of alveoli are reduced and many of those remaining are enlarged, making the lungs of the patient with emphysema less elastic and overinflated. Due to the higher pressure inside the chest that mustbe developed to force air out of the less elastic lungs, the bronchioles, small air tubes of the respiratory system, tend to collapse during exhalation.Stale air gets trapped in the air sacs, and fresh air cannot be brought in.

In the general population, emphysema usually develops in older individuals with a long smoking history. However, there is also a form of emphysema that runs in families. People with this type of emphysema have a hereditary deficiency of a blood component, an enzyme inhibitor called alpha-1-antitrypsin (AAT). This type of emphysema is sometimes called early onset emphysema because itcan appear when a person is as young as 30 or 40 years old. It is estimatedthat there are between 75,000 and 150,000 Americans who were born with AAT deficiency. Of this group, emphysema afflicts an estimated 20,000-40,000 people(1-3% of all cases of emphysema). The risk of developing emphysema for an AAT-deficient individual who also smokes is much greater than for others.

The first symptoms of chronic bronchitis are cough and mucus production. These symptoms resemble a chest cold that lingers on for weeks. Later, shortnessof breath develops. Cough, sputum production, and shortness of breath may become worse if a person develops a lung infection. A person with chronic bronchitis may later develop emphysema as well. In emphysema, shortness of breath on exertion is the predominant early symptom. Coughing is usually minor and there is little sputum. As the disease progresses, the shortness of breath occurs with less exertion, and eventually may be present even when at rest. At this point, a sputum-producing cough may also occur. Either chronic bronchitisor emphysema may lead to respiratory failure--a condition in which there occurs a dangerously low level of oxygen or a serious excess of carbon dioxide inthe blood.

The first step in diagnosing COPD is a good medical evaluation, including a medical history and a physical examination of the chest using a stethoscope. In addition, the doctor may order further tests such as a test of pulmonary function to measure the air taken into and exhaled from the lungs, a chest x ray, and blood gas levels to determine the amount of oxygen and carbon dioxidepresent in the blood.

The precise nature of the patient's condition determines the type of treatment prescribed for COPD. With a program of complete respiratory care, disability can be minimized, acute episodes prevented, hospitalizations reduced, and some early deaths avoided. On the other hand, no treatment has been shown to slow the progress of the disease, and only oxygen therapy increases survival rate.

Medications frequently prescribed for COPD patients include bronchodilaters to open narrowed airways, corticosteroids to block inflammation, oxygen replacement (from portable or stationary tanks), and antibiotics to combat respiratory infection, among others.

Surgical procedures for emphysema are very rare. The great majority of patients cannot be helped by surgery, and no single procedure is ideal for those who can be helped.

A structured, outpatient pulmonary rehabilitation program helps the lungs tooperate more effectively in certain patients with COPD. Services may includegeneral exercise training, administration of oxygen and nutritional supplements, intermittent mechanical ventilatory support, continuous positive airway pressure, relaxation techniques, breathing exercises and techniques (such as pursed lip breathing), and methods for mobilizing and removing secretions.

COPD is a disease that can be treated and controlled, but not cured. Survivalof patients with COPD is clearly related to the degree of their lung function when they are diagnosed and the rate at which they lose this function. Overall, the median survival is about 10 years for patients with COPD who have lost approximately two-thirds of their lung function at diagnosis. In other words, these patients have a fifty-fifty chance of surviving more than 10 years.

Lifestyle modifications that can help prevent COPD, or improve function in COPD patients, include quitting smoking, avoiding respiratory irritants and infections, avoiding allergens, maintaining good nutrition, drinking lots of fluids, avoiding excessively low or high temperatures and very high altitudes, maintaining proper weight, and exercising to increase muscle tone.

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