Airway Remodeling

Airway Remodeling

Summary

Airway remodeling refers to the changes that occur in the airway wall due to asthma-induced inflammation. Airway remodeling is usually permanent and can cause irreversible decline in lung function. Because the airway is compromised in people with airway remodeling, it takes less to set off symptoms and the condition often leads to more frequent asthma attacks.

Damage from airway remodeling occurs when the cells or muscles that line the airway become inflamed or sensitive. It can also occur when cells grow faster than normal, or when an abnormal amount of mucus accumulates in the airways.

While the damage itself is permanent, regular use of anti-inflammatory medications can slow or prevent further airway damage. These medications should be taken on a regular basis, even when symptoms are not present. Individuals with chronic asthma should work closely with their physicians to control their asthma symptoms and limit airway remodeling.

About airway remodeling

Airway remodeling is the structural changes that occur in the large and small airways as a result of chronic asthma inflammation. This damage often leads to a thickening of the airway wall and a decline in lung function (the ability to move air in and out of the lungs). According to the American Academy of Allergy, Asthma and Immunology, as many as 92 percent of patients with asthma experience some thickening of the bronchial wall in the large and small airways.

Airway remodeling usually occurs as a result of chronic asthma or COPD (chronic obstructive pulmonary disease). However, smoking cigarettes is also linked to airway remodeling. Acute asthma can cause less damage associated with minor airway remodeling.

The damage sustained during airway remodeling often results in asthma exacerbations such as increased asthma attacks and sensitivity to triggers (e.g., dander, pollen, mold), as well as difficulty breathing. This damage can also cause a diminished response to asthma medications. Airway remodeling often results in the following types of damage:

  • Cellular inflammation. Cells dilate and grow larger, constricting airways.

  • Airway wall thickening. The walls of both the large and small airways can grow thicker as cellular growth is stimulated by perceived damage.

  • Smooth muscle growth. The muscle mass of the smooth muscle increases in both the large and small airways, reducing the patient’s ability to inhale air into the lungs.

  • Epithelium erosion. This thin layer of protective cells that lines the airways becomes fragile and begins to erode and slough (shed). This further blocks the airways.

  • Mucus increase. The number and size of mucous glands located throughout the airways increases, reducing the diameter of airways and generating greater amounts of mucus than normal.

The permanent destructive changes associated with airway remodeling involve several different mechanisms. Unfortunately, little is known about why these mechanisms are triggered and clinical studies are ongoing. These changes include:

  • Destruction of elastic tissue in the airways. As the smooth muscles contract, the elastic tissue normally works as an opposing force to keep the muscles in check. However, once the elastic tissue is damaged (which is believed to be due to inflammation), the contracting muscles tighten without opposition, constricting the airways.

  • Thickened airways. This often leads to hyperresponsiveness in the bronchial tubes, which leads to more frequent asthma attacks.

  • Increase in the bulk of the smooth muscles, cellular growth and the increased production of mucus. These changes block the airways, increasing the number of breathing difficulties as well as sensitivity to attacks.

Treatment & prevention of airway remodeling

The damage sustained as a part of airway remodeling is irreversible. However, treating inflammation early and regularly (with anti-inflammatory drugs) in patients with chronic asthma is believed to slow or even prevent airway remodeling. Patients who are suffering from ongoing asthma conditions should work closely with their physician to avoid or limit permanent airway damage. Many patients with asthma do not use medications appropriately – bronchodilators tend to be overused and corticosteroids tend to be underused. It is important to use medications as directed by the physician.

The damage is believed to be the result of what is essentially one of the body’s defense mechanisms operating unchecked. Hence, it is difficult for researchers to find a therapy that can reverse airway remodeling damage without damaging the body’s ability to repair itself. While very little is known about the successful reversal of airway remodeling damage, there are some preventative measures currently available that work by preventing inflammation in the airway.

The most frequently-used method for controlling inflammation in the airway, improving asthma management and preventing airway remodeling involves the use of corticosteroids. These drugs are very effective at preventing inflammation and can be taken on a regular basis as a preventative controller of asthma symptoms.

Early studies seem to indicate that corticosteroid drugs, when taken before serious damage has occurred in the airways, can prevent long-term decline in lung function. The drugs may also be capable of preventing or reducing the damage caused by airway remodeling. However, this research is preliminary.

While the current research is not conclusive, most physicians stress the use of anti-inflammatory drugs – even when the asthma patient feels fine – to decrease the chances of severe airway remodeling damage developing. Inflammation is often present in an asthma patient’s lungs even during those periods where they feel fine. It is important that individuals with asthma always continue to take their regular anti-inflammatory treatments, even during symptom-free periods.

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about airway remodeling:

  1. Am I at risk for airway remodeling?

  2. Do my symptoms indicate airway remodeling?

  3. What may have caused me to develop airway remodeling?

  4. Does airway remodeling pose a danger to my overall health?

  5. Is the damage that has occurred reversible?

  6. Are there any treatments available to me?

  7. How does airway remodeling affect my asthma?

  8. What steps can I take to prevent further airway remodeling?
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