asthma

[همسه]

What Is Asthma?

Asthma (AZ-ma) is a chronic (long-term) lung disease that inflames and narrows the airways. Asthma causes recurring periods of wheezing (a whistling sound when you breathe), chest tightness, shortness of breath, and coughing. The coughing often occurs at night or early in the morning.

Asthma affects people of all ages, but it most often starts in childhood. In the United States, more than 22 million people are known to have asthma. Nearly 6 million of these people are children.

Overview

The airways are tubes that carry air into and out of your lungs. People who have asthma have inflamed airways. This makes the airways swollen and very sensitive. They tend to react strongly to certain substances that are breathed in.

When the airways react, the muscles around them tighten. This causes the airways to narrow, and less air flows to your lungs. The swelling also can worsen, making the airways even narrower. Cells in the airways may make more mucus than normal. Mucus is a sticky, thick liquid that can further narrow your airways.

This chain reaction can result in asthma symptoms. Symptoms can happen each time the airways are irritated.




Figure A shows the location of the lungs and airways in the body. Figure B shows a cross-section of a normal airway. Figure C shows a cross-section of an airway during asthma symptoms.

What Causes Asthma?

The exact cause of asthma isn't known. Researchers think a combination of factors (family genes and certain environmental exposures) interact to cause asthma to develop, most often early in life. These factors include:


An inherited tendency to develop allergies, called atopy
Parents who have asthma
Certain respiratory infections during childhood
Contact with some airborne allergens or exposure to some viral infections in infancy or in early childhood when the immune system is developing
If asthma or atopy runs in your family, exposure to airborne allergens (for example, house dust mites, cockroaches, and possibly cat or dog dander) and irritants (for example, tobacco smoke) may make your airways more reactive to substances in the air you breathe.

Who Is At Risk for Asthma?

Asthma affects people of all ages, but it most often starts in childhood. In the United States, more than 22 million people are known to have asthma. Nearly 6 million of these people are children.

Young children who have frequent episodes of wheezing with respiratory infections, as well as certain other risk factors, are at the highest risk of developing asthma that continues beyond 6 years of age. These risk factors include having allergies, eczema (an allergic skin condition), or parents who have asthma.

Among children, more boys have asthma than girls. But among adults, more women have the disease than men. It's not clear whether or how sex and sex hormones play a role in causing asthma
Most, but not all, people who have asthma have allergies.

Some people develop asthma because of exposure to certain chemical irritants or industrial dusts in the workplace. This is called occupational asthma.



What Are the Signs and Symptoms of Asthma?

Common asthma symptoms include:

Coughing. Coughing from asthma is often worse at night or early in the morning, making it hard to sleep.
Wheezing. Wheezing is a whistling or squeaky sound that occurs when you breathe.
Chest tightness. This may feel like something is squeezing or sitting on your chest.
Shortness of breath. Some people who have asthma say they can't catch their breath or they feel out of breath. You may feel like you can't get air out of your lungs.

How Is Asthma Diagnosed?

Medical History
Physical Exam
Diagnostic Tests
Lung Function Test
Other Tests
Allergy testing to find out which allergens affect you, if any.
A test to measure how sensitive your airways are. This is called a bronchoprovocation test. Using spirometry, this test repeatedly measures your lung function during physical activity or after you receive increasing doses of cold air or a special chemical to breathe in.
A test to show whether you have another disease with the same symptoms as asthma, such as reflux disease, vocal cord dysfunction, or sleep apnea.
A chest x ray or an EKG (electrocardiogram). These tests will help find out whether a foreign object or other disease may be causing your symptoms

Diagnosing Asthma in Young Children

young child who has frequent wheezing with colds or respiratory infections is more likely to have asthma if:

One or both parents have asthma
The child has signs of allergies, including the allergic skin condition eczema
The child has allergic reactions to pollens or other airborne allergens
The child wheezes even when he or she doesn't have a cold or other infection

How Is Asthma Treated and Controlled?

Asthma is treated with two types of medicines: long-term control and quick-relief medicines. Long-term control medicines help reduce airway inflammation and prevent asthma symptoms. Quick-relief, or "rescue," medicines relieve asthma symptoms that may flare up.

Long-Term Control Medicines

Inhaled corticosteroids
Inhaled long-acting beta2-agonists
Leukotriene modifiers
Cromolyn and nedocromil
Theophylline

Quick-Relief Medicines

Inhaled short-acting beta2-agonists