Asthma

Asthma is a disorder of the respiratory system in which the passages that enable air to pass into and out of the lungs periodically narrow, causing coughing, wheezing, and shortness of breath. This narrowing is typically temporary and reversible, but in severe attacks, asthma may result in death. Asthma most commonly refers to bronchial asthma, an inflammation of the airways, but the term is also used to refer to cardiac asthma, which develops when fluid builds up in the lungs as a complication of heart failure. This article focuses on bronchial asthma.

More than 17 million Americans suffer from asthma, with nearly 5 million cases occurring in children under age 18. In the United States, asthma causes nearly 5,500 deaths each year. Asthma occurs in males and females of all ages, ethnic groups, and socioeconomic levels. For reasons not completely understood, asthma is generally more common in poor urban neighborhoods, in cold climates, and in industrialized countries.

Among all Americans, the prevalence of asthma increased more than 60 percent between 1982 and 1994, especially among children. Deaths from asthma increased more than 55 percent from 1979 to 1992. Scientists suspect that increased exposure to second-hand cigarette smoke, growing populations in polluted city centers, and new housing that is poorly ventilated contribute to the increase in asthma cases.

Breathing

Every cell in the human body requires oxygen to function, and the lungs make that oxygen available. With every breath we take, air travels to the lungs through a series of tubes and airways. After passing through the mouth and throat, air moves through the larynx, commonly known as the voice box, and then through the trachea, or windpipe. The trachea divides into two branches, called the right bronchus and the left bronchus, that connect directly to the lungs. Air continues through the bronchi, which divide into smaller and smaller air passages in the lungs, called bronchioles. The bronchioles end in clusters of tiny air sacs, called alveoli, which are surrounded by tiny, thin-walled blood vessels called capillaries.

Here, deep in the lungs, oxygen diffuses through the alveoli walls and into the blood in the capillaries and gaseous waste products in the blood—mainly carbon dioxide—diffuse through the capillary walls and into the alveoli. But if something prevents the oxygen from reaching t...

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...ng, may provoke hyperventilation, a rapid inhalation of oxygen that causes the airway to narrow. In asthmatics, hyperventilation often results in an attack. Many asthmatics are especially sensitive to physical exercise in cold weather.

Research suggests that genetic factors may increase the risk of developing the disorder. Children with a family history of asthma are more likely to develop asthma than other children. Despite this apparent genetic link, many people without a family history of asthma develop the disorder, and scientists continue to investigate additional causes.

Treatment

Physicians typically diagnose asthma by looking for the classic symptoms: episodic problems with breathing that include wheezing, coughing, and shortness of breath. When symptoms alone fail to establish a diagnosis of asthma, doctors may use spirometry, a test that measures airflow. By comparing a patient’s normal airflow, airflow during an attack, and airflow after the application of asthma medication, doctors determine whether the medicine improves the patient’s breathing problems. If asthma medication helps, doctors usually diagnose the condition as asthma.

Bibliography

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