What is Severe Asthma?
Researchers have learned that 5-10 percent of asthmatics do not respond well to traditional asthma medications, making their asthma difficult to control. In order to better help these asthmatics, researchers now categorize them under a special asthma subtype called severe asthma, also known as Therapy-Resistant Asthma or Asthma COPD Overlap Syndrome. So, what is severe asthma, and what does it mean if you have it?
Defining severe asthma
Sally Wenzel, professor of medicine at the University of Pittsburgh, defines severe asthma as “patients who require high dose inhaled glucocorticoid (GC), or continuous or near continuous oral GC treatment to maintain asthma control or who never achieve control despite that treatment.” Different methodologies have been used to identify subtypes of asthma, including severe asthma.
Conditions commonly mistaken for severe asthma
Severe asthma must not be confused with other causes of "difficult to treat asthma", including:
Asthma exacerbated by uncontrolled asthma triggers (i.e. allergic asthma caused by exposure to molds)
Asthma that is poorly controlled due to nonadherence (i.e. not taking medicines as prescribed)
Disorders that mimic asthma (i.e. sinus infections)
What does a diagnosis of severe asthma mean?
A diagnosis of severe asthma, when confirmed, will include:
Chronic Airway Inflammation: This makes airways hypersensitive to asthma triggers, causing the smooth muscles surrounding them to spasm. This narrows or obstructs the airways. A second response is increased sputum production, further obstructing airways. This causes intermittent asthma symptoms like wheezing and shortness of breath. This response is completely reversible, and can be prevented and treated with typical asthma medications. This is seen in all asthmatics.
Airway Remodelling: This is also referred to as airway scarring. It’s associated with a permanent thickening of the walls lining airways, particularly smaller airways. This makes them chronically narrowed or chronically obstructed. The cause of this remains a mystery, although some speculate it has to do with asthma left untreated long-term, or too many severe asthma attacks. Another common cause is chronic inhalation of chemicals, such as those in tobacco and wood smoke. It causes persistent symptoms; it makes you feel short of breath even on a good asthma day. This response is irreversible, and there is at present no treatment. This is similar to what happens in COPD, and is only present in severe asthmatics.
These two components together act as a "double whammy", making asthma difficult to control. This probably means you also have:
Air trapping: Air can get past chronically narrowed airways but has a hard time getting back out. This causes air to become trapped inside your lungs.
Airflow limitation: This is best observed by a prolonged expiration. Sometimes it may seem you can exhale forever and never get all the air out. You can't generate enough flow to blow out a candle.
Fewer treatment options: No medicine treats airway remodelling. You respond poorly to traditional asthma medications, like inhaled corticosteroids. [Bronchial thermoplasty] can be effective in some individuals with severe asthma.
More frequent and severe asthma attacks: Their airways are increasingly brittle and narrow making them increasingly prone to more severe attacks compared to those with typical asthma.
Lots of doctor appointments: They'll need to see doctors who specialize in this type of asthma. They are also prone to more frequent and unscheduled doctor visits compared to those with typical asthma.
Lots of fees: While they consist of only 5-10 percent of asthmatics, they consume up to half the cost of asthma in both the U.S. and Europe.
Unanswered questions: So, why is it that only 5-10 percent of asthmatics develop severe asthma? Researchers are working overtime to answer this question and to create special guidelines and medicinal options to help them achieve optimal control of their disease.
What do we currently know about severe asthma?
Researchers believe the immune response that occurs in severe asthmatics is different than what occurs in traditional asthmatics. For instance, immune cells (called CD4-TH2 cells) secrete different inflammatory proteins than the same cells in traditional asthmatics. This makes their airways hypersensitive in such a way that does not respond sufficiently and effectively to corticosteroids.
Since patients with severe asthma experience most of the deaths associated with asthma and have more hospitalizations, it’s important to identify individuals with risk. Identifying the phenotypes in certain individuals prone to develop severe (resistant) asthma can allow physicians to tailor treatment to these individuals. The net result should be reduced symptoms, less progression of disease and lower health costs.
It’s important to note that there is some disagreement among the organizations that currently set the guidelines for classification of severe asthma. When it is diagnosed, patients need to be educated so that they understand when it is not safe to remain at home because high grade treatment like intravenous magnesium sulfate, assistance in ventilation or possible short-term intubation may be necessary.
It is well established that severe asthma accounts for a majority of healthcare costs for asthma. The true impact of severe asthma on people's lives was revealed in a survey released in September, 2015. Of 850 severe asthmatics surveyed, 25 percent reported daily symptoms, and 71 percent reported weekly symptoms. Likewise, 32 percent said it affected their social life, 23 percent said it affected their working life, 18 percent said it affected their family life, and 17 percent said it affected their sex life.
In conclusion, a proper diagnosisan should lead your doctor to the best treatment options to help you obtain ideal control of your disease, reducing hospitalizations and complications. Ongoing research should equal better breathing in the near future for all asthmatics.