Asthma

  • Basics

    Asthma is a chronic respiratory disease that causes difficulty breathing Figure 01. Asthma is caused by inflamed and constricted airways brought on by an allergic reaction or an environmental trigger. It is potentially life-threatening, but is controllable. Asthma often begins in childhood, even as early as infancy; however, it can occur at any age, even among elderly individuals.

    In asthma, the airways become narrowed, thereby trapping air and causing the lungs to become overinflated. The narrowing can occur in varying degrees over a short period of time, causing mild to severe breathing difficulty during an attack.

    Asthma affects more than 15 million people in the U.S., where the disease is responsible for more than 5,000 deaths each year. It is the most common chronic disease of childhood. While asthma can be very disruptive, frustrating, and expensive, if properly controlled, the likelihood of danger and discomfort decreases significantly.

    Asthma attacks can begin suddenly, or they can take days to develop. An asthma attack occurs when the airways undergo changes due to respiratory infection, allergies, irritants, and other environmental triggers.

    The inflammation of asthma causes recurrent episodes of wheezing, breathlessness, tightening of the chest, and coughing. The episodes often occur at night or in the early morning hours.

    Asthma is thought to have two primary stages: hyper-reactivity and the inflammatory response. The first stage, hyper-reactivity (also referred to as hyper-responsiveness), occurs when the smooth muscles in the airways constrict and narrow when exposed to inhaled allergens or other irritants. The airways of someone with asthma do not relax, making breathing difficult. The second stage is the inflammatory response. This reaction causes the airways to swell, fill with fluid, and produce thick, sticky mucus. You then experience wheezing and breathlessness, have difficulty exhaling, and have a cough that produces phlegm.

    Asthma attacks can be mild or severe. If you are having a mild to moderate attack, you may experience a tight sensation in the chest, wheezing, coughing, and difficulty sleeping. After you take asthma medication, the airways usually open up within a few minutes and the symptoms diminish.

    If you are having a severe asthma attack, you will become increasingly breathless, and your neck muscles may become tight. The lack of oxygen will cause your skin to turn bluish, and the skin between your ribs will appear to be sucked in. You may even lose consciousness. Both asthma medication and emergency medical assistance are essential during a severe attack.

    Click to enlarge: Anatomy of the lungs and inflamed airways

    Figure 01. Anatomy of the lungs and inflamed airways

  • Causes

    An asthma attack is usually triggered by something that bothers the lungs. The exact causes of asthma are complex and varied, and it is often difficult to determine precisely what initiates an attack. Genetic susceptibility and environmental triggers are among the factors believed to cause asthma. Intense exercise, especially when performed in cold air, may induce asthma. Asthma usually is worse at night when the airways are cooler, mucus does not clear as effectively, and the metabolism of medications can become altered. Sleep apnea may also be related to the incidence of asthma attacks. Sleep apnea is a disorder that occurs when the body “forgets” to breathe. Breathing ceases for a few seconds (sometimes as much as two minutes, or more) during sleep, but not as a result from an obstruction in the airways. The muscles that control breathing simply don't function correctly.

    Viral infections can be potent triggers. Viral respiratory infections, including the common cold and influenza, can be triggers for a severe asthmatic attack. Viral infections may be the main factor that causes chronic asthma.

    The common cold (rhinovirus) is one of the most common infectious agents associated with asthma attacks, and it can provoke and intensify asthma attacks.

    Allergens can initiate or perpetuate asthma. Airborne pollens, molds, dust, animal dander, and cockroach allergen can trigger asthmatic attacks. The dust mite, a component of house dust, is one of the key causes of asthma symptoms. Dust mites are invisible to the naked eye, and live in bedding, fabric, and carpet. Tobacco and wood smoke, perfume, paint, hair spray, or any other fumes can play a role in triggering asthma attacks. Food allergens or additives also are believed to trigger asthma.

    There is an association between gastroesophageal reflux disease (GERD) and asthma. Gastroesophageal reflux disease (GERD) causes heartburn when acid from the stomach creeps into the esophagus. The condition is common in many patients with asthma. Some researchers believe that GERD may cause asthma when the acid spill reaches the throat. The irritation this acid causes to the trachea (the tube which brings air in and out of the body) is believed to trigger spasms and narrowing of the airways in the lungs.

    Gastroesophageal reflux often is made worse with the use of oral theophyline, a commonly used bronchodilator medicine that helps stop asthma attacks. Reflux can be made worse because the bronchodilator medicine relaxes the gastroesophageal sphincter, thus allowing even more highly acidic digestive fluids to leak out of the stomach.

    Hormones may be involved in asthma. Some patients whose bodies produce too much thyroid hormone (hyperthyroidism) have persistent asthma. In asthmatic women, asthma frequently gets worse before menstrual periods.

    There is a close association between sinusitis and asthma. Sinusitis is an inflammation or infection of the air pockets on either side of and behind the nose. A reflex from the inflamed sinuses can trigger an asthma attack.

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