For many years, asthma was viewed as a disease of airway narrowing, or bronchoconstriction. In the traditional view, the bronchial passages, especially those encircled by specialized muscle fibers, became narrowed or constricted, and an inevitable “attack” would follow. The traditional explanation emphasized that constriction of the bronchial tubes was the primary event in asthmatics. The focus of asthma treatment centered on attempts at reversing constricted breathing passages. Consequently, treatment consisted mostly of relief of airway narrowing once symptoms developed and became established. Emphasis was placed on treatment of “attack” symptoms, rather than on preventive measures.
The principal “player” or “culprit” in asthma is inflammation.
The contemporary perspective on asthma recognizes the importance of bronchoconstriction, but assigns it a secondary role. The principal “player” or “culprit” in asthma is inflammation. In the contemporary model of asthma, asthmatics experience periods of active disease or exacerbation, along with quiescent periods of remission (Table Asthma: Quiescent versus Exacerbated). During an exacerbation, there is increased inflammatory activity in the asthmatic lung. The inflammation, if unchecked, leads to mucus gland stimulation with excess secretions, and to eventual bronchoconstriction, or airway narrowing. The increased mucus leads to cough. The bronchoconstriction is responsible for symptoms of breathlessness, wheezing, and chest tightness.
Table Asthma: Quiescent versus Exacerbated
|Inactive, asymptomatic asthma||Active, exacerbated asthma|
|Inflammation absent, quiescent||Heightened inflammation|
|Air passages are clear of mucus||Mucus production increases => leads to cough, clear mucus|
|Air tubes are patent, “fully” open||Air tubes narrow, constrict=> leads to wheezing, tightness, breathlessness|
Individuals with asthma have a propensity to develop an enhanced inflammatory response in their lungs. They are said to have an innate state of lung “baseline hyperreactivity.” A specialized lung test, called the methacholine challenge (bronchoprovocation) test, is helpful to clinicians when evaluating individuals suspected of having asthma and a state of lung hyperreactivity
The tendency to increased baseline hyperreactivity is likely hereditary
Increased baseline hyperreactivity explains why, for example, asthmatics are more “sensitive” to inhalation of different environmental stimuli such as cold air, strong odors, or cigarette smoke. The presence of bronchial hyperreactivity is of great interest to asthma researchers. It is tempting to speculate about a medication that could modify a person’s bronchial hyperreactivity and so reduce the severity of his or her asthma.
The current understanding of asthma as a disease primarily of inflammation, with secondary airway narrowing and constriction as a consequence of an increased inflammatory response, has both research and practical implications. It allows for preventive interventions and for more directed medications. Controlling and limiting airway inflammation controls asthma symptoms and allows for normal lung function, an excellent prognosis, and a healthy lifestyle. Prompt treatment of an exacerbation, if and when it occurs, always includes anti-inflammatory treatment in addition to specific treatment of bronchoconstriction. Recognition of the importance of inflammation in asthma has lead to a better understanding of asthma, and to the development of more effective treatment.
Asthma exacerbations often occur predictably and inevitably following certain exposures, such as the onset of cold winter temperatures, for example. Some individuals “get an attack” every fall at the change of season and must forego daily routines including work and school, or avoid leisure activities. Treatment of established symptoms of “an attack” in the traditional view might include a burst of medications, hopefully in the office setting, but possibly in the hospital. The contemporary view of asthma, however, emphasizes a preventative approach (Table The Contemporary View of Asthma).
Table The Contemporary View of Asthma
|The modern view of asthma emphasizes the all-important role of inflammation.|
|Consequently, contemporary asthma treatment includes:• avoiding factors that increase lung inflammation |
• medications that have anti-inflammatory properties
|The traditional view erroneously assigned a primary role to airway narrowing (bronchoconstriction).|
|Bronchoconstriction, or airway narrowing, is the consequence of a more powerful stimulus: airway inflammation.|
An asthmatic individual with a pattern of worsening symptoms at the change of season would be prescribed anti-inflammatory medication as winter approached, for example. By successfully controlling inflammation, and by being alert to early signs and symptoms of disease exacerbation, “attacks” would be avoided, along with significant lifestyle disruptions.