Asthma Chapter 6
Don't Lose Control
Long-Term Consequences of Uncontrolled AsthmaThere is no cure for asthma, but its symptoms can be managed. By using appropriate medications, the inflammation that characterizes the disease can usually be kept under control, and the number and severity of your asthma attacks can be reduced. READ MORE
If the inflammation of asthma is uncontrolled, the result may be lasting physical changes to the structure of the cells and tissues of your lungs. The walls of the airways can thicken and the interior of your airways narrow permanently, in a way that medications can’t help. This is especially true if your asthma is severe. This process is called airway remodeling.
Fortunately, it has been shown in studies that treating asthma early with inhaled corticosteroids can often keep inflammation under control, so that airway remodeling doesn’t occur. LESS
What Happens in Airway Remodeling?Uncontrolled asthma alters the lungs in a number of important ways:
- Muscle tissue enlarges. The amount of muscle mass increases in both the large and small airways (the large bronchi and the bronchioles), contributing to bronchospasm (contraction of the smooth muscle of the airways). Airway muscle tissue mass may increase three to four times the amount normally present. In a thickened airway wall, smooth muscle tissue needs to contract by only a small amount in order to completely close the airway.
- New blood vessels form and vessels dilate. A dense network of capillaries underlies your airways. In asthma, these capillaries dilate (widen) and new vessels form, termed angiogenesis, adding to the thickness of the airway wall. In addition, the new vessels are very permeable and increase edema (swelling) in the airway tissue.
- Scar tissue forms. The connective cells of the airway walls normally produce a number of different molecules that fill the spaces around the cells of your airways, called the extracellular matrix. In people with asthma, some of these structural molecules, particularly collagen, are produced in abnormal amounts, creating airway fibrosis—scar tissue in the airway wall.
- Mucus glands increase. Mucus glands are normally found in the tissue of the larger, or cartilaginous, airways (internal diameter of >2 mm). In people with asthma, they are found there and also in the smaller peripheral bronchioles, where they are not normally found. In addition, in asthma there are more mucus glands present in the airway wall, resulting in a greater amount of mucus being secreted. The mucus they secrete is also denser and less liquid than normal mucus. Most fatal attacks of asthma are caused by suffocation due to mucus plugging the airways.
Effects of Airway Remodeling: ThickeningThe end result of airway remodeling: the airway wall thickens, and the airway itself becomes narrower. All the parts of the airway wall—inner, outer, and total—thicken in people with asthma. The thickness of the airways was found to increase as much as 300% in cases of nonfatal asthma, and up to 100% in cases of fatal asthma. It’s likely that the airways increase more in size in more severe cases of asthma.
Effects of Airway Remodeling: HyperresponsivenessAll these changes have the effect of making the lungs even more hyperresponsive to triggers. In addition, the increased thickness of the outer wall of the airways may allow them to detach from the surrounding lung tissue, which normally helps to tether the airways and keep them open. This permits the smooth muscle to contract more, further narrowing the airway. READ MORE
What’s more, it seems that there is a vicious circle at work in airway remodeling. Although inflammation of the airways over time accounts for hyperresponsiveness and subsequently airway remodeling, it also seems that the remodeling itself then contributes to airway hyperresponsiveness. LESS
Is Airway Remodeling Permanent?For many years, asthma was considered a completely reversible condition. And, in fact, for many patients who have mild asthma or who maintain treatment with corticosteroid therapy, the symptoms of asthma are reversible, and there is no permanent remodeling of the airways. READ MORE
However, in the past two decades researchers have found that some patients do experience permanent remodeling of their airways. This happens most often in cases of severe asthma, when inflammation is not being kept under control with corticosteroid therapy, or when anti-inflammatory therapy is started later in the course of the disease.
It’s worth noting that these permanent structural changes can happen even in young patients and in people who have experienced asthma but have no further symptoms. LESS
What Does This Mean for People with Asthma?When airway remodeling occurs, the usual medications for opening the airways may prove ineffective, even at maximal doses. This is obviously very dangerous. It points to the need for keeping inflammation under control continuously and beginning anti-inflammatory treatment early. READ MORE
Unfortunately, this often doesn’t happen. One study reported that 72% of men and 86% of women with asthma had symptoms 15 years after their initial diagnosis of asthma. Only 19% of these people, however, were still seeing a doctor, and only 32% used any maintenance medication. LESS
The material on this site is for informational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any medical condition. Consult a licensed medical professional for the diagnosis and treatment of all medical conditions and before starting a new diet or exercise program. If you have a medical emergency, call 911 immediately.