The diagnosis of asthma is based on constriction of the small airways of the lung. The small airway constriction can occur intermittently or may be present chronically, on a daily basis. Even when asthma is chronic, the degree of airway constriction is variable resulting in the variability of symptoms.
There are two major mechanisms of small airway constriction. The treatment for each mechanism is different and both mechanisms usually must be treated for effective control of asthma. One mechanism of small airway constriction involves the constriction of smooth muscle bands that are wrapped around the small airways. The second mechanism involves inflammation of the inner lining of the small airway. The resulting swelling and excess mucus production impinge upon the opening of the airway. The constriction of the smooth muscle bands, the swelling of the airway lining, and the excess mucus production combine together to block the flow of air through the small airways. This is why asthma is often referred to as “small airways disease” and “airway obstruction”.
In contrast, bronchitis is a disease of the larger airways. Inflammation also occurs in bronchitis but the site of inflammation is the large airways. There is excess mucus production in bronchitis but there is no airway obstruction because the larger airways are so large that air still flows easily through them. The inflammation in both asthma and bronchitis can be triggered by a viral infection. In fact, many patients with
asthma develop both small and large airway inflammation when a virus infects their lungs.
With bronchitis, the viral infection can sometimes progress to a bacterial infection manifested by a cough productive of purulent sputum (green/yellow colored mucus). The production of purulent sputum usually indicates the need for treatment with antibiotics. Antibiotics have no effect on viruses so they are not used in most cases of viral triggered asthma. Instead, they are used for bronchitis with purulent sputum.
Treatment of asthma is aimed at the two mechanisms of small airway constriction. Albuterol or similar “rescue inhaler” gives fast relief by reversing the smooth muscle constriction mechanism. Various anti-inflammatory medications are used to treat the inflammatory mechanism of asthma. It can take several days of consecutive use for anti-inflammatory medications to begin to work so it is important to use the anti-inflammatory medications daily when they are prescribed.
Treatment of asthma should also include avoiding potential triggers. Just as viral infection of the lungs is a trigger for some asthmatics, cold air, airborne irritants, tobacco smoke, and allergens can be a trigger for many asthmatics. Allergy testing can identify allergy triggers and specific steps can be taken to avoid some allergens.
If asthma symptoms persist after taking steps to avoid allergens, allergy shots can sometimes help to make a person less sensitive to their allergic triggers.
Authored by Robert Settipane, MD