Asthma is a clinical syndrome of chronic airway inflammation characterized by recurrent, reversible, airway obstruction. Airway inflammation also leads to airway hyperreactivity, which causes airways to narrow in response to various stimuli.
Asthma is a common chronic condition, affecting 68 per thousand individuals in most recent asthma surveys. Asthma remains a leading cause of missed workdays. It is responsible for 1.5 million emergency department visits annually and up to 500,000 hospitalizations. Over 3,300 Americans die annually from asthma. Furthermore, as is the case with other allergic conditions, such as eczema (atopic dermatitis), hay fever (allergic rhinitis), and food allergies, the prevalence of asthma appears to be on the rise.
Asthma is characterized by reversible airway narrowing, whereas COPD (chronic obstructive pulmonary disease) typically has fixed airway narrowing.
Some symptoms of COPD are similar to asthma, including wheezing, shortness of breath, and cough.
The cough in COPD can be more productive of mucus than asthma, and patients with severe COPD may need oxygen supplementation.
COPD is very often a result of cigarette smoke exposure, either direct or secondhand, although severe asthma can evolve to COPD over time in the absence of smoke exposure.
Medications used to treat COPD include inhaled corticosteroids, bronchodilators, inhaled corticosteroid/bronchodilator combinations, long-acting muscarinic antagonists, and oral steroids.
There is a newly described syndrome called asthma/COPD overlap syndrome that displays characteristics of both asthma and COPD. This is an area of medicine that needs further study.
Asthma results from complex interactions between an individual's inherited genetic makeup and interactions with the environment. The factors that cause a genetically predisposed individual to become asthmatic are poorly understood. The following are risk factors for asthma:
Family history of allergic conditions
Personal history of hay fever (allergic rhinitis)
Viral respiratory illness, such as respiratory syncytial virus (RSV), during childhood
Exposure to cigarette smoke
Lower socioeconomic status
Exposure to air pollution or burning biomass
Asthma may not be the same in different affected individuals. Asthma specialists currently use a variety of clinical data to categorize a patient's asthma. This data includes the age of asthma onset, the presence or absence of environmental allergies, the presence or absence of elevated blood or sputum levels of eosinophils (a type of white blood cell), lung function testing (spirometry and fractional excretion of nitric oxide), obesity, and cigarette smoke exposure.
Types: T2 high or non T2 (T2 low)
Your doctor may refer to asthma as being "allergic" or "eosinophilic." One or both of these characteristics make up a "T2 high" phenotype of asthma, which is the term for the type of immune inflammation associated with asthma. The allergic type typically develops in childhood and is associated with environmental allergies, which approximately 70%-80% of children with asthma have. Typically, there is a family history of allergies. Additionally, other allergic conditions, such as food allergies or eczema, are often also present. Allergic asthma often goes into remission in early adulthood. However, in many cases, the asthma reappears later. Sometimes allergic asthma can appear with elevated blood or sputum eosinophils. Asthma that develops in adulthood may be associated with sputum or blood eosinophils but without environmental allergies. Sometimes patients in this category also have nasal polyps, which are eosinophil-rich growths in the nasal lining.
Non T2 asthma, or T2 low asthma, comprises a smaller yet difficult to treat proportion of asthma that is not associated with allergies or eosinophils. This type of asthma is sometimes called "neutrophilic asthma" and may be associated with obesity.
The classic signs and symptoms of asthma are shortness of breath, cough (often worse at night), and wheezing (high-pitched whistling sound produced by turbulent airflow through narrow airways, typically with exhalation). Many patients also report chest tightness. It is important to note that these symptoms are episodic, and individuals with asthma can go long periods without any symptoms.
Common triggers for asthmatic symptoms include exposure to allergens (pets, dust mites, cockroach, molds, and pollens), exercise, and viral infections. Other triggers include strong emotion, odor exposure, and temperature extremes. Tobacco use or exposure to secondhand smoke complicates asthma management.
Many of the symptoms and signs of asthma are nonspecific and can be seen in other conditions as well. Symptoms that might suggest conditions other than asthma include new symptom onset in older age, the presence of associated symptoms (such as chest discomfort, lightheadedness, palpitations, and fatigue), and lack of response to appropriate medications for asthma.
The physical exam in asthma is often completely normal. Occasionally, wheezing is present. In an asthma exacerbation, the respiratory rate increases, the heart rate increases, and the work of respiration increases. Individuals often require accessory muscles to breathe, and breath sounds can be diminished. It is important to note that the blood oxygen level typically remains fairly normal even in the midst of a significant asthma exacerbation. Low blood oxygen level is therefore concerning for impending respiratory failure.
The diagnosis of asthma begins with a detailed history and physical examination. Primary-care providers are familiar with the diagnosis of asthma, but specialists such as allergists or pulmonologists may be involved. A typical history is an individual with a family history of allergic conditions or a personal history of allergic rhinitis who experiences coughing, wheezing, and difficulty breathing, especially with exercise, viral infections, or during the night. In addition to a typical history, improvement with a trial of appropriate medications is very suggestive of asthma.
In addition to the history and exam, the following are diagnostic procedures that can be used to help with the diagnosis of asthma:
Lung function testing with spirometry: This test measures lung function as the patient breathes into a tube. If lung function improves significantly following the administration of a bronchodilator, such as albuterol, this essentially confirms the diagnosis of asthma. It is important to note, however, that normal lung function testing does not rule out the possibility of asthma.
Measurement of exhaled nitric oxide (FeNO): This can be performed by a quick and relatively simple breathing maneuver, similar to spirometry. Elevated levels of exhaled nitric oxide are suggestive of T2 inflammation seen in some types of asthma.
Skin testing for common aeroallergens: The presence of sensitivities to environmental allergies increases the likelihood of asthma. Of note, skin testing is more accurate than blood work (in vitro testing) for environmental allergies. Testing for food allergies is not indicated in the diagnosis of asthma.
Doctors often perform blood tests for the allergic antibody (IgE) and eosinophils to establish the present of T2 high asthma.
Other potential but less commonly used tests include provocation testing such as a methacholine challenge, which tests for airway hyperresponsiveness. Hyperresponsiveness is the tendency of the breathing tubes to constrict or narrow in response to irritants. A negative methacholine challenge makes asthma unlikely. Specialists sometimes also measure sputum eosinophils, another marker for "allergic" inflammation seen in asthma. Chest X-rays or CT-scans may show hyperinflation, but are often normal in asthma. Tests to rule out other conditions, such as cardiac testing, may also be indicated in certain cases.
The treatment goals for asthma are to:
adequately control symptoms,
minimize the risk of future exacerbations,
maintain normal lung function,
maintain normal activity levels, and
take the least amount of medication possible with the least amount of potential side effects.
Inhaled corticosteroids (ICS) are the most effective anti-inflammatory agents available for the chronic treatment of asthma and are first-line therapy per most asthma guidelines. It is well recognized that ICS are effective in decreasing the risk of asthma exacerbations. Furthermore, the combination of a long-acting bronchodilator (LABA) and an ICS has a significant additional beneficial effect on improving asthma control. Short-acting rescue inhalers are the standard of care for break through symptoms.
Short-acting bronchodilators (albuterol [Proventil, Ventolin, ProAir, ProAir RespiClick, Maxair, Xopenex]) provide quick relief for symptoms occurring despite controller medications. These may also be used alone in patients with occasional symptoms or patients experiencing symptoms with exercise only. Inhaled steroids (budesonide [Pulmicort Turbuhaler, Pulmicort Respules], fluticasone [Flovent, Arnuity Ellipta, Armon Air RespiClick], beclomethasone [Qvar], mometasone [Asmanex], ciclesonide [Alvesco], flunisolide [Aerobid, Aerospan]) are first-line anti-inflammatory therapies.
Long-acting bronchodilators (salmeterol [Serevent], formoterol [Foradil], vilanterol) can be added to ICS as additive therapy. LABAs should never be used alone for the treatment of asthma.
ICS/LABA combination agents combine corticosteroids and long-acting bronchodilators. Fluticasone/salmeterol (Advair, AirDuo, Wixela), budesonide/formoterol (Symbicort), fluticasone/vilanterol (Breo), mometasone/formoterol (Dulera).
Leukotriene modifiers (montelukast [Singulair], zafirlukast [Accolate], zileuton [Zyflo]) can also serve as anti-inflammatory agents.
Anticholinergic agents or antimuscarinic agents (ipratropium [Atrovent, Atrovent HFA], tiotropium [Spiriva], umeclidinium [Incruse Ellipta]) can help decrease sputum production.
There is one triple combination agent of an inhaled corticosteroid, long-acting bronchodilator, and anti-muscarinic agent: fluticasone/vilanterol/umeclidium (Trelegy) that is most often used for asthma/COPD overlap.
Anti-IgE treatment (omalizumab [Xolair]) can be used in allergic asthma.
Anti-IL5 treatment (mepolizumab [Nucala], reslizumab [Cinqair], and benralizumab [Fasenra]) can be used in eosinophilic asthma.
Anti IL-4 receptor antagonist (dupilumab, Dupixent) is approved for moderate to severe eosinophilic asthma. It is also approved for atopic dermatitis and nasal polyposis.
Chromones (cromolyn [Intal, Opticrom, Gastrocrom], nedocromil [Alocril]) stabilize mast cells (allergic cells) but are rarely used in clinical practice.
Theophylline (Respbid, Slo-Bid, Theo-24) also helps with bronchodilation (opening the airways) but is rarely used in clinical practice due to an unfavorable side-effect profile.
Systemic steroids (prednisone [Deltasone, Liquid Pred], prednisolone [Flo-Pred, Pediapred, Orapred, Orapred ODT], methylprednisolone [Medrol, Depo-Medrol, Solu-Medrol], dexamethasone [DexPak]) are potent anti-inflammatory agents that are routinely used to treat asthma exacerbations but pose numerous unwanted side effects if used repeatedly or chronically.
Numerous additional monoclonal antibodies are also currently being studied and will likely be available within the next couple of years.
Immunotherapy or allergy shots have been shown to decrease medication reliance in allergic asthma.
There are no home remedies that have proven benefit for asthma.
There is often concern about potential long-term side effects of inhaled corticosteroids. Numerous studies have repeatedly shown that even long-term use of inhaled corticosteroids has very few if any sustained, clinically significant side effects, including changes in bone health, growth, or weight. However, the goal always remains to treat all individuals with the least amount of medication that is effective. Patients with asthma should be routinely reassessed for any appropriate changes to their medical regimen.
Asthma medications can be administered via inhalers either with or without a spacer or nebulized solution. It is important to note that if an individual has proper technique with an inhaler, the amount of medication deposited in the lungs is no different than that when using a nebulized solution. When prescribing asthma medications, it is essential to provide the appropriate teaching on proper delivery technique.
Smoking cessation and/or minimizing exposure to secondhand smoke are critical when treating asthma. Treating concurrent conditions such as allergic rhinitis and gastroesophageal reflux disease (GERD) may also improve asthma control. Vaccinations such as the annual influenza vaccination and pneumonia vaccination are also indicated.
Although the vast majority of individuals with asthma are treated as outpatients, treatment of severe exacerbations can require management in the emergency department or hospital. These individuals typically require use of supplemental oxygen, early administration of systemic steroids, and frequent or even continuous administration of bronchodilators via a nebulized solution. Individuals at high risk for poor asthma outcomes are referred to a specialist (pulmonologist or allergist). The following factors should prompt consideration or referral:
History of ICU admission or multiple hospitalizations for asthma
History of multiple visits to the emergency department for asthma
History of frequent or daily use of systemic steroids for asthma
Ongoing symptoms despite the use of appropriate medications
Significant allergies contributing to poorly controlled asthma
Patients experiencing acute asthma symptoms should first use their rescue inhaler (albuterol). If asthma symptoms are worsening and use of albuterol is increasing, then asthma patients should have a medical evaluation. A course of oral steroids may be indicated and an adjustment in asthma maintenance therapy may be needed. If symptoms are rapidly progressive, asthma patients should seek emergency medical care.
The prognosis for asthma is generally favorable. Children experience complete remission more often than adults. Although adults with asthma experience a greater rate of loss in their lung function as compared to age-controlled counterparts, this decline is usually not as severe as seen in other conditions, such as chronic obstructive pulmonary disease (COPD) or emphysema. Asthma in the absence of other comorbidities does not appear to shorten life expectancy. Risk factors for poor prognosis from asthma include
a history of hospitalizations, especially ICU admissions or intubation,
frequent reliance on systemic steroids,
significant medical comorbidities.
The airway narrowing in asthma may become fixed over time and can resemble COPD or emphysema. The other main complication of asthma is due to side effects from oral steroid use, which can include bone loss (osteoporosis), weight gain, and glucose intolerance.
With the increasing prevalence of asthma, numerous studies have looked for risk factors and ways to potentially prevent asthma. It has been shown that individuals living on farms are protected against wheezing, asthma, and even environmental allergies. The role of air pollution has been questioned in both the increased incidence of asthma and in regards to asthma exacerbations.
Climate change is also being studied as a factor in the increased incidence of asthma. Maternal smoking during pregnancy is a risk factor for asthma and poor outcomes. Tobacco smoke is also a significant risk factor for the development and progression of asthma. Treatment of environmental allergies with allergen immunotherapy, or allergy shots, has been shown to decrease a child's risk of developing asthma. The development of asthma is ultimately a complex process influenced by many environmental and genetic factors, and currently there is no proven way to decrease an individual's risk of developing asthma.