Asthma and Airway Inflammation: The Big Picture
Asthma is a chronic inflammatory disorder. This inflammation causes the airway swelling and narrowing which leads to airway constriction. The symptoms of asthma—wheezing, shortness of breath, chest tightness, and coughing are due to this constriction.
Airway constriction can be measured using traditional lung function tests such as spirometry. However, while measuring airway constriction is important, it may not tell the whole story. In many cases, lung function tests may be normal, but airway inflammation can be present. This may indicate a potential loss of asthma control. When the airway inflammation is high it may indicate a higher risk of hospitalization or the need to go to the emergency room due to asthma.
Understanding airway inflammation
Airway inflammation is most frequently caused by exposure to allergens such as seasonal pollens, mold spores, and indoor allergens (e.g., animals or dust mites).
High levels of nitric oxide (NO) in the breath are a sign of allergic airway inflammation, and people with asthma have higher concentrations of NO in their breath than those without asthma. The measure of the concentration of NO in the breath is referred to as fractional exhaled nitric oxide, or FeNO. There is a simple, noninvasive breath test that is now available to measure FeNO.
In 2011, the American Thoracic Society published a guideline for the use of FeNO in asthma management. They concluded that FeNO is directly related to allergic airway inflammation and that it can be reliably used to assess and manage asthma. FeNO does not replace spirometry or a physician’s clinical assessment, but it can be an additional valuable tool to assist asthma management. Treating asthma effectively means taking into account the patient’s history, appropriate use of diagnostic tests, and appropriate interpretation of test results by a skilled physician who has been specially trained to diagnose and treat asthma.
It is critical that the physician know how to appropriately utilize certain testing modalities and also know how to tailor treatment based off of correct interpretation. Many studies have shown that regularly measuring airway inflammation using FeNO can help specialists prevent asthma exacerbations in their patients and also better manage the patients’ long-term asthma control. In particular, pregnant women whose asthma was managed by FeNO had fewer asthma exacerbations and, neonatal hospitalizations were also reduced. FeNO allows better control of asthma in pregnant women with the least medication.
Long-term asthma management
The preferred asthma therapies are inhaled steroids—they are highly effective in controlling asthma symptoms. However, they are associated with risks that necessitate close monitoring. The FeNO test is an inexpensive test that is used routinely in my office for effective monitoring of asthma inflammation. This, in combination with other tests such as spirometry and accurate allergy testing, make our approach to diagnosing and treating asthma highly effective.
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