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What is Asthma?

Kelly Fan, MD Kelly Fan, MD
Medically reviewed by Susan Kerrigan, MD and Marianne Madsen on February 17, 2023

Asthma is a chronic lung disease affecting 300 million people worldwide characterized by reversible airflow obstruction, airway hyperreactivity, and airway inflammation. Broadly speaking, there are two primary types of asthma. The first type is eosinophilic T2 high asthma which usually develops in childhood and is linked to allergies. The second type is non-eosinophilic T2 low asthma. This asthma phenotype is not as well defined and possibly associated with smoking, occupational exposures, environmental pollutants, chronic acid reflux, frequent viral infections, or obesity. Treatment principles for both broad types of asthma are consistent but advanced therapies are currently much better studied in eosinophilic T2 high asthma.


What are the symptoms seen in patients with asthma?


Asthma is characterized by episodes of airflow obstruction causing chest tightness, wheezing, chronic cough, and shortness of breath. In between episodes, asthmatics can often feel normal without many, if any, pulmonary symptoms. Exposure to a particular pollen during the spring season or exercise leading to airway constriction are common triggers that can lead to worsening asthma symptoms. It’s important for asthmatics to identify and avoid the triggers that set off their symptoms. Most patients with asthma do well over time, needing only rescue inhalers sporadically. However, patients with poorly controlled asthma can develop fixed airflow obstruction. This implies a permanent loss of lung function and need for stronger inhaler therapies on a daily basis.


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Asthma - Overview

Asthma - Overview

How is asthma diagnosed?


Asthma is diagnosed with a combination of clinical history, physical examination, imaging studies, and laboratory tests. Most cases of asthma can be suggested by the clinical history and physical examination. However, asthma symptoms are nonspecific and other conditions can share similar symptoms. Additional tests are sometimes needed to distinguish asthma from these other conditions such as COPD or bronchiectasis. A chest x-ray or CT scan is often normal in asthmatics but may show airway dilation, inflammation, and mucous plugging in a patient with bronchiectasis. Blood work that would suggest a diagnosis of asthma include high IgE antibody levels and elevated eosinophils (a type of blood cell).


Pulmonary function testing is perhaps the most widely ordered study by pulmonologists. These are non-invasive tests in which a patient breathes into the testing apparatus, allowing quantification of how well the lungs are functioning.


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Asthma - Diagnosis

The patterns seen on the pulmonary function testing will help define the degree and type of lung impairment. It is used in all lung diseases including asthma, COPD, bronchiectasis, interstitial lung disease, pulmonary hypertension, lung cancer, and pleural diseases. In asthmatics, pulmonary function testing helps with diagnosis and trending disease progression. Monitoring how a patient’s pulmonary function testing changes can suggest how well a patient is responding to treatment.


How is asthma managed?


A combination of lifestyle interventions and inhaler medications are the cornerstone of asthma management. In patients with more advanced disease, subcutaneous biological therapies and bronchoscopy procedures can be considered.


All patients with asthma should consider lifestyle changes including regular exercise and healthy dietary habits high in fruits and vegetables to maintain a BMI under 25. Going to sleep no earlier than 3 hours after completing dinner will minimize the risk of gastric reflux and chronic aspiration which can decrease nocturnal asthma symptoms. These lifestyle changes can be difficult to implement but making small and incremental progress leads to sustained results.


There are many inhalers on the market available for asthma patients. The severity and frequency of a patient’s symptoms will help determine the inhalers that need to be prescribed. Patients with mild asthma may only need the short-acting inhalers which can be taken on an as-needed basis. In patients with more persistent symptoms, maintenance inhaler therapies are needed. Maintenance inhalers include medications such as inhaler corticosteroids and smooth muscle relaxants. These medications will decrease inflammation and help open up airways. It’s important to distinguish between one’s maintenance inhaler and an as-needed inhaler. As the names imply, maintenance inhalers should be used on a daily basis regardless of a patient’s symptoms. As-needed short-acting inhalers only need to be used when a patient’s symptoms worsen or prior to exercise. There are a few oral medications that can be added onto maintenance inhaler therapies. These oral medications block the inflammatory cascade that results in asthma symptoms.


For patients with difficult-to-control T2 high eosinophilic asthma, there are newer biological agents that can be considered. These medications are administered subcutaneously at set intervals, such as every 4 weeks. The biological agents decrease episodes of asthma exacerbation and improve daily symptoms.


Finally, bronchial thermoplasty is a procedure that can be performed at specialized centers for patients with severe asthma. This procedure applies heat directly to the airways and reduces smooth muscle airway mass. The goal of this procedure is to improve quality of life and decrease frequent need for short-acting rescue inhalers. It should be noted this is a risky procedure and only experienced centers should be offering this procedure.


Managing asthma is often a daily challenge, but if patients keep on top of the symptoms, they can experience a much better quality of life.


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Asthma - Management

Doctor Profile

Kelly Fan, MD


Dr. Fan is a pulmonologist and critical care attending physician with clinical expertise in advanced asthma, bronchiectasis, bronchoscopy, COPD, interstitial lung disease, lung cancer, lung infections, pleural disease, and pulmonary vascular disease. Dr. Fan is a Doctorpedia Founding Medical Partner and the Chief Medical Officer of Doctorpedia's Lung Health channel.

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