emDOCs Podcast – Episode 36: Severe Asthma and Mimics

Background

Asthma is common, affecting 1 in 11 children and 1 in 12 adults in the U.S. Asthma lacks a clear definition, despite it being a common disease. The Global Initiative for Asthma defines it as “a heterogeneous disease, usually characterized by chronic airway inflammation. It is defined by the history of respiratory symptoms such as wheeze, shortness of breath, chest tightness, and cough that vary over time and in intensity, together with variable expiratory airflow limitation.”

An asthma exacerbation often presents with wheezing and prolonged expiration. Patients with severe respiratory distress may present in a tripod position, leaning forward. The most dangerous lung sound is the absences of air movement, which is due to severe bronchoconstriction or patient exhaustion.

There are many mimics of asthma, especially conditions that present with wheezing. Some patients may present with no wheezing, but most report obstructive type symptoms. Over 75% of COPD patients and nearly 30% of patients with cardiac pathology experience similar symptoms. Airways narrow through swelling, compression, and intrinsic compression, and this narrowing with turbulent air flow can result in wheezing. Emergency physicians should be aware of conditions that can result in similar symptoms. Lung findings on exam are explained below.

Asthma Mimics

Anaphylaxis: Anaphylaxis involves two organ systems or a known allergic exposure with low blood pressure. Exam usually reveals urticaria (10-20% will not have rash), and nausea, vomiting, or diarrhea may also be observed. Treatment requires immediate resuscitation with epinephrine, steroids, intravenous (IV) fluids, and histamine antagonists.  Any concern for anaphylaxis warrants intramuscular epinephrine.⁴

COPD: Like asthma, COPD is an obstructive airway disease. Patients may have asthma/COPD overlap. Official diagnosis is often completed by pulmonologist, though asthma is usually diagnosed in young adulthood and COPD usually after age 40 with history of bronchodilator responsiveness, Initial treatment of COPD is similar to asthma, though long term medication management differs (such as Long Acting Beta Agonists (LABA) in COPD improving mortality). In asthma, LABA use may increase mortality if used without inhaled steroids.

Heart Failure: Heart failure may result in wheezing with lung fluid accumulation.  Some patients may not be diagnosed with heart failure upon initial presentation, and patients may present acutely with respiratory distress or with chronic worsening orthopnea and dyspnea (the most common presentation). Flash pulmonary edema (the acute version) can be due to ischemia, acute valvular pathology, cardiomyopathy, and other conditions. Exam may reveal rales, S3 heart sound, elevated JVP, and edema. Patients may have a history of dyspnea with exertion or with lying flat.  Acute exacerbation with pulmonary edema requires venodilators and positive pressure ventilation (CPAP or BPAP). Diuretics can be used after venodilation.

PE: PE is not always an easy diagnosis, though emergency physicians evaluate patients with potential PE on a regular basis. Close to 1 in 10 patients with PE may have wheezing on exam.This may be due to vasoactive mediators released in response to the embolus.The key is to evaluate for PE risk factors in the history. If patients do not improve with standard asthma medications, PE should also be considered. Evaluation includes risk stratification such as Wells criteria, with D-dimer and CT pulmonary as needed. Significant PE requires anticoagulation.

Foreign body aspiration: A small object in the bronchioles from aspiration can result in focal lung finds, and worse, respiratory distress. Patients with greatest risk for this include children, older adults, and those mentally disabled. Patients may present with acute cough or wheezing. The classic history is lack of preceding upper respiratory symptoms or prior wheezing. Choking followed by cough is present in 75% of pediatric patients with foreign body aspiration.  Chest x-ray can help, erect and lateral, which may show hyperinflation.  Bronchoscopy is required if concern for aspiration, even with negative chest x-ray.

Angioedema: “Angioedema” refers to localized swelling in locations with loose connective tissue, including the face, oropharynx, bowel wall, extremities, and genitalia. There are many causes. Primary pathology includes mast cell-mediated and bradykinin-mediated. Mast-cell mediated angioedema can have other signs of allergic reaction such as urticaria. Bradykinin-induced angioedema is not associated with urticaria and pruritis, as it is not allergic. This form is the cause in ACE-inhibitor-induced angioedema and hereditary angioedema. Angioedema associated with systemic findings such as upper airway swelling, wheezing, abdominal pain, nausea, and vomiting should be managed as anaphylaxis until proven otherwise and treated with epinephrine, antihistamines, and corticosteroids. Rapid airway protection with intubation may be required, and a difficult airway should be assumed with adjuncts available.

Drug Related Wheezing: This is most commonly associated with aspirin. Aspirin Exacerbated Respiratory Disease, or Samter’s Triad, consists of asthma, nasal polyps, and sensitivity to aspirin or other NSAIDs. Non-selective beta-blockers can precipitate wheezing in patients with underlying disease (such as asthma). ACE-inhibitors, while commonly causing dry cough, may result in bronchospasm and wheezing. Many drugs can cause asthma symptoms, or worsen asthma in patients with known disease. The risks and benefits of continuing aspirin or an NSAID must be strongly considered, or an alternative can be used.

Central Airway Obstruction: Obstruction in the trachea and main stem bronchi include bronchogenic carcinomas, tracheal strictures, sarcoidosis, and goiter. Though these usually do not present acutely, patients may notice other symptoms including weight loss. If the obstruction is fixed, wheezing will likely be constant and fixed. Asthmatic wheezing usually occurs after exposure to allergen or upper respiratory infection. Wheezing due to fixed obstruction may be localized on exam. Further evaluation and testing relies on the history and exam. Risk factors for cancer, symptoms consistent with hyperthyroidism, or a history of intubation should be obtained. Chest CT will most likely identify the obstruction, though the patient must be able to lie supine. Further consultation is required if diagnosed, with bronchoscopy as well.

Vocal Cord Dysfunction: Paradoxical, involuntary closure of the vocal cords during inspiration, (or edema of the vocal cords) may result in wheezing and acute respiratory distress. Wheezing in this condition is usually inspiratory or inspiratory and expiratory (asthmatic wheezing is mostly expiratory). This is due to forced expiration stenting open the cords and decreasing the obstruction. Patients often present soon after exposure to a stressor, inhaled irritants, or exercise. Risk factors include prior intubation or neck surgery (leading to possible damage to the recurrent laryngeal nerve). Diagnosis is often confirmed through laryngoscopy. Treatment of vocal cord dysfunction includes several maneuvers. Panting, which can abduct the vocal cords through activation of the posterior cricoarytenoids, breathing through a straw, patient jaw thrust while breathing, nose to mouth breathing, administration of a helium-oxygen mixture such as heliox, or continuous positive airway pressure (CPAP) can be used. The condition is often self-limited and usually does not require other invasive interventions.