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This patient's physical examination and imaging findings are consistent with a diagnosis of acute severe asthma. Agitation, breathlessness during rest, and a respiratory rate > 30 breaths/min are some manifestations of an acute severe episode. During severe episodes, accessory muscles of respiration are usually used, and suprasternal retractions are often present. The heart rate is > 120 beats/min and the respiratory rate is > 30 breaths/min. Loud biphasic (expiratory and inspiratory) wheezing can be heard, and pulsus paradoxus is often present (20-40 mm Hg). Oxyhemoglobin saturation with room air is < 91%. As the severity increases, the patient increasingly assumes a hunched-over sitting position with the hands supporting the torso, termed the tripod position.
Asthma is a chronic, heterogenous inflammatory airway disorder characterized by variable expiratory flow; airway wall thickening; respiratory symptoms; and exacerbations, which sometimes require hospitalization. According to the World Health Organization, asthma affected an estimated 262 million people in 2019. The presence of airway hyperresponsiveness or bronchial hyperreactivity in asthma is an exaggerated response to various exogenous and endogenous stimuli. Mechanisms implicated in the development of asthma include direct stimulation of airway smooth muscle and indirect stimulation by pharmacologically active substances from mediator-secreting cells, such as mast cells or nonmyelinated sensory neurons. The degree of airway hyperresponsiveness is associated with the clinical severity of asthma.
Acute severe asthma is a life-threatening emergency characterized by severe airflow limitation that is unresponsive to the typical appropriate bronchodilator therapy. As a result of pathophysiologic changes, airflow is severely restricted in severe asthma, leading to premature closure of the airway on expiration; impaired gas exchange; and dynamic hyperinflation, or air-trapping. In such cases, urgent action is essential to thwart serious outcomes, including mechanical ventilation and death.
Asthma severity is defined by the level of treatment required to control a patient's symptoms and exacerbations. According to the 2022 Global Initiative for Asthma (GINA) guidelines, a severe asthma exacerbation describes a patient who talks in words (rather than sentences); leans forward; is agitated; uses accessory respiratory muscles; and has a respiratory rate > 30 breaths/min, heart rate > 120 beats/min, oxygen saturation on air < 90%, and peak expiratory flow ≤ 50% of their best or of predicted value. Given the heterogeneity of asthma, patients with acute severe asthma may present with a variety of signs and symptoms, including dyspnea, chest tightness, cough and wheezing, agitation, drowsiness or signs of confusion, and significant breathlessness at rest.
Exposure to external agents, such as indoor and outdoor allergens, air pollutants, and respiratory tract infections (primarily viral), are the most common causes of asthma exacerbations, which vary in severity. Numerous other factors can trigger an asthma exacerbation, including exercise, weather changes, certain foods, additives, drugs, extreme emotional expressions, rhinitis, sinusitis, polyposis, gastroesophageal reflux, menstruation, and pregnancy. Importantly, a patient with known asthma of any level of severity can experience an asthma exacerbation, including patients with mild or well-controlled asthma.
Patients with a history of poorly controlled asthma or a recent exacerbation are at risk for an acute asthma exacerbation. Other risk factors include poor perception of airflow limitation, regular or overuse of short-acting beta agonists, incorrect inhaler technique, and suboptimal adherence to therapy. Comorbidities associated with risk for an acute asthma exacerbation include obesity, chronic rhinosinusitis, inducible laryngeal obstruction (vocal cord dysfunction), gastroesophageal reflux disease, chronic obstructive pulmonary disease, obstructive sleep apnea, bronchiectasis, cardiac disease, and kyphosis due to osteoporosis (followed by corticosteroid overuse). The lack of a written asthma action plan and socioeconomic factors are also associated with increased risk for a severe exacerbation.
In the emergency department setting, pharmacologic therapy of acute severe asthma should consist of a short-acting beta agonist, ipratropium bromide, systemic corticosteroids (oral or intravenous), and controlled oxygen therapy. Clinicians may also consider intravenous magnesium sulfate and high-dose inhaled corticosteroids. Once stable, patients should be treated with optimal asthma-controlling therapy, as outlined in GINA guidelines. Optimizing patients' inhaler technique and adherence to therapy are imperative, and comorbidities should be appropriately managed. Nonpharmacologic interventions, such as smoking cessation, pulmonary rehabilitation, exercise, weight loss, and influenza/COVID-19 vaccination, are also recommended as indicated.
Zab Mosenifar, MD, Medical Director, Women's Lung Institute; Executive Vice Chairman, Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California.
Zab Mosenifar, MD, has disclosed no relevant financial relationships.
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