at: inbox

Pulmonology - Asthma - Fast Facts | NEJM Resident 360

Asthma is a chronic lung disease characterized by airway inflammation that manifests as intermittent episodic coughing, wheezing, dyspnea, and chest tightness. The symptoms and severity of asthma are variable and often driven by hyperresponsiveness to environmental stimuli, including respiratory infections, allergens, exercise, weather, and emotions. Physiologically, the disease is characterized by variable expiratory airflow limitation that is reversible with appropriate therapy or preventable by avoiding triggers.

Inflammatory, Immunologic, and Pathobiologic Features Leading to Severe Asthma

(Source: Severe and Difficult-to-Treat Asthma in Adults. N Engl J Med 2017.)

Assessment

Symptoms: The pretest probability for a diagnosis of asthma is increased in patients with typical episodic patterns of wheeze, dyspnea, and chest tightness.

History: A personal or family history of atopy in a patient with characteristic symptoms further supports this diagnosis.

S****pirometry: Testing is necessary for diagnosis and to distinguish reversible airflow limitation characteristic of asthma versus other causes of dyspnea, such as chronic obstructive pulmonary disease (COPD). (See spirometry testing below.)

Classification of severity: Asthma is categorized into four levels of severity (intermittent, mild persistent, moderate persistent, and severe persistent) that help guide asthma therapy.

Initial Treatment: Adult or Adolescents with a Diagnosis of Asthma

(Source: ©2021 Global Initiative for Asthma, reprinted with permission. Available from www.ginasthma.org)

Physical exam: The physical exam for asthma is limited.

• Wheezing is the most distinguishing feature but does not predict the severity of underlying disease (and can be absent outside of exacerbation). The asthmatic wheeze is described as polyphonic, high-pitched, and musical. It is typically worse on expiration and multifocal in location. Asthma is correlated with allergic rhinitis and nasal polyposis. For common exam findings in allergic rhinitis, please see the Allergy/Immunology rotation guide.

• In more severe cases look for use of accessory muscles of ventilation, sternal retraction at the onset of a breath, more than 10 mmHg of pulsus paradoxus.

Investigations

Spirometry: Spirometry testing is fundamental to both diagnosis and follow up of asthma will be normal. When the patient is symptomatic, spirometry will show a reduced FEV₁  and evidence of airway obstruction (i.e., reduced FEV₁/FVC ratio). After administration of a short-acting bronchodilator, an increase in FEV₁ or FVC >200 mL and ≥12% from baseline is diagnostic of a bronchodilator response and consistent with asthma. Diurnal variation of peak expiratory flow >10%, or visit-to-visit variability of >200 mL and ≥12% can also be diagnostic.

The diagnosis of asthma can also be made by demonstrating airway hyper-responsiveness via bronchoprovocational testing (i.e., the methacholine challenge).

Blood testing: Routine blood testing is not necessary for a diagnosis of asthma but may be indicated to aid in treatment decisions if the patient has normal spirometry and no response to bronchodilator testing.

• Blood eosinophil levels and serum IgE are both important markers of disease and necessary to inform the decision to use advanced therapy.

• Allergen testing may be helpful to inform trigger avoidance in patients with an allergic component to their disease. Patients with suspected asthma-associated conditions, such as eosinophilic granulomatosis with polyangiitis or allergic bronchopulmonary aspergillosis, may also require additional blood work.

• The fraction of nitric ovide in the exhaled air (Fe_NO) is associated with airway inflammation. Levels above 30 ppb (in a nonsmoker on no treatment) help confirm an asthma diagnosis.

Treatment

Glucocorticoids: In contrast with primary use of bronchodilators in the treatment for COPD, the hallmark of treatment for asthma is inhaled glucocorticoids.

Monoclonal antibodies: The introduction of monoclonal antibodies targeting inflammatory pathways central to asthma pathogenesis has transformed asthma therapy; these are usually used under the supervision of asthma care specialists.

Stepwise approach: The 2020 update of the U.S. National Asthma Education and Prevention Program (NAEPP) and the 2021 update of the Global Initiative for Asthma (GINA) guidelines recommend that treatment of asthma involve a continuous cycle of assessment, adjustment, and review and a stepwise approach to the number of medications and frequency of dosing with the objective of using the least amount of medication needed to control symptoms and reduce risk of exacerbations (see figure below based on the NAEPP update of 2020).

Note: There is controversy about whether as needed short-acting β-agonist (SABA) should be used alone or with an inhaled glucocorticoid whenever used; the latter is the approach advocated in the 2021 GINA guideline.

• Treatment should begin with proper patient education, trigger avoidance, and management of comorbidities. Proper inhaler technique is fundamental to adequate medication delivery. See a brief video of multidose inhaler technique.

• GINA advocates for starting therapy with as-needed budesonide–formoterol combination inhalers (inhaled glucocorticoids with long-acting beta-agonist) whereas NAEPP continues to support the use of a short-acting bronchodilator (e.g., albuterol) alone as a first step. The subsequent step in the NAEPP guideline is an as-needed budesonide–formoterol combined inhaler. An alternative is for patients to take low-dose inhaled glucocorticoids whenever short-acting bronchodilators are used.

• If the priority is symptom control (as opposed to prevention of exacerbation), daily low-dose inhaled glucocorticoids can be used instead of as-needed budesonide–formoterol.

• An alternative to the addition of a long-acting beta-agonist (LABA; e.g., formoterol) to a glucocorticoid inhaler is the addition of a leukotriene modifier or a long-acting anti-muscarinic. These agents can also be added on to treatment with an inhaled glucocorticoid–LABA combination if additional controller medications are needed.

• If further control is needed, the patient should be referred to an asthma specialist to rule out other asthma-associated conditions and to consider biologic therapy.

• Monoclonal antibody therapy: Omalizumab, an anti-IgE drug, was the first monoclonal antibody agent approved for use in patients with allergic asthma that is not controlled by inhaled therapy. In patients with uncontrolled eosinophilic asthma, anti–interleukin-5 (mepolizumab, reslizumab), anti–interleukin-5 receptor (benralizumab), and anti–interleukin-4 receptor (dupilumab) antibodies have shown efficacy in reducing excaerbations; dupilumab also improves lung function modestly.

Ages 12+ Years: Stepwise Approach for Management of Asthma

(Source: 2020 Focused Updates to the Asthma Management Guidelines: A Report from the National Asthma Education and Prevention Program Coordinating Committee Expert Panel Working Group. Allergy Clin Immunol 2020.)

Asthma Exacerbation

Asthma exacerbation is common and potentially life-threatening if not managed emergently. The following approach can be used to manage an acute exacerbation.

Initial Assessment of a Patient Presenting to the Emergency Department with Asthma

(Source: Emergency Treatment of Asthma. N Engl J Med 2010.)

Continued Management of Asthma in the Emergency Department

(Source: Emergency Treatment of Asthma. N Engl J Med 2010.)

inbox