Asthma is an obstructive pulmonary disorder with exacerbations characterized by symptoms of shortness of breath, cough, chest tightness, and/or wheezing. Symptoms are caused by chronic airway inflammation. There are multiple cell types and inflammatory mediators involved in its pathophysiology. The airway inflammation is frequently mediated by Th2 lymphocytes, whose cytokine secretion leads to mast cell stimulation, eosinophilia, leukocytosis, and enhanced B-cell IgE production. Although various genes have been identified as likely contributors to asthma development, asthma is largely environmentally triggered and has a multifactorial cause. Asthma is extremely common, especially in poor, urban environments. Asthma is the third most common reason for pediatric hospitalizations.
Key points
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Cardinal asthma symptoms are shortness of breath, cough, chest tightness, and/or wheezing.
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Symptoms arise from airway inflammation, which leads to airway edema, remodeling, and hyperresponsiveness.
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The inflammation in asthma is mediated by multiple cell types including mast cells, eosinophils, lymphocytes, macrophages, neutrophils, and epithelial cells, and there is a predominantly Th2 milieu.
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The cause of asthma is a multifactorial. Active research in asthma genetics has replicated genes that likely play a role in asthma development, but phenotype expression is profoundly affected by environmental triggers.
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Roughly 8% of the US population has asthma and it is the third leading cause of hospitalization in children, accounting for roughly $56 billion per year in direct costs and lost productivity.
What is asthma?
Asthma is a chronic inflammatory disorder characterized by airway obstruction and hyperresponsiveness. The medical term “asthma,” which derives from the Greek for “panting,” was named by Hippocrates around 400 bc . Sir William Osler described asthma in his Principles and Practice of Medicine in the early 20th century as “swelling of the nasal or respiratory mucous membrane, increased secretion, and…spasm of the bronchial muscles with dyspnea, chiefly expiratory.” Of its treatment, he said, “Ordinary tobacco cigarettes are sometimes helpful.” (This position is no longer considered true.) Many decades later, it is now understood that asthma is a complex disease of airway inflammation characterized by airway edema, remodeling, and hyperresponsiveness. Asthma exacerbations are characterized by progressively worsening shortness of breath, cough, chest tightness, and/or wheezing. Under this umbrella of clinical symptoms, there is a very sophisticated interplay between underlying genotypes and environmental triggers that is only partially understood. This leads to a broad array of variable disease phenotypes and manifestations. Asthma is increasingly recognized as a syndrome, rather than an illness.
Diagnosis
The diagnosis of asthma is made when episodic symptoms of airflow obstruction or airway hyperresponsiveness are present, airflow obstruction is partially reversible, and alternative diagnoses are excluded. In addition to a good medical history and physical examination, spirometry is needed to demonstrate obstruction and assess reversibility. Reversibility is determined by an increase in forced expiratory volume in 1 second (FEV 1 ) of greater than or equal to 12% from baseline or an increase greater than or equal to 10% of predicted FEV 1 after inhalation of a short-acting β 2 -agonist. The National Institutes of Health Guidelines for the Diagnosis and Management of Asthma recommend considering a diagnosis of asthma when certain key indicators are present ( Table 1 ). The key indicators consist of specific symptoms, physical examination findings, and modifying factors and environmental exposures. There is a great deal of overlap between asthma symptoms and other disorders of the respiratory tract. The differential diagnosis for asthma symptoms includes allergic rhinitis or sinusitis, foreign body, aspiration, gastroesophageal reflux, laryngotracheomalacia, vocal cord dysfunction, bronchiolitis, chronic obstructive pulmonary disease, and cystic fibrosis, among other conditions. Recurrent cough and wheezing should always alert practitioners to the possibility of asthma.
| Symptoms | Physical Examination Findings | Modifying Factors |
|---|---|---|
| Wheezing (recurrent) Cough, worse at night Difficulty breathing (recurrent) Chest tightness (recurrent) | Thoracic hyperexpansion Wheezing during normal breathing Prolonged phase of forced exhalation Rhinorrhea Nasal polyps Atopic dermatitis | Exercise Viral infection Animals with fur or hair Dust mites Mold Smoke Pollen Changes in weather Airborne chemicals or dusts Menstrual cycles |
Asthma can be intermittent or persistent, and it can present with acute flares or chronic symptoms. Asthma severity is measured by objective measures of lung function (ie, spirometry or peak flow meter) and by symptoms. Measures of impairment include nighttime awakenings, need for short-acting bronchodilators, work or school days missed, ability to engage in normal daily activities, and quality of life assessments. The frequency of exacerbations in the population with asthma varies widely. Importantly, the severity of disease (as measured by frequency of nighttime awakenings, usage of short-acting β 2 -agonists, and interference with normal activity) does not correlate with the intensity of exacerbations. Indeed, severe, life-threatening exacerbations can occur even in people with intermittent or mild asthma when provoked by an exposure, such as a viral illness, irritant, or allergen. However, decreased FEV 1 in children demonstrates a strong association with the risk of asthma exacerbations. In terms of modifying factors, viral infections are the most common cause of asthma exacerbations.
There is a traditional division between allergic and nonallergic asthma. Allergic asthma is the subtype that accounts for approximately 50% to 80% of asthma cases, and is defined as asthma and positivity to skin prick test or specific IgE. Allergic asthma is more common in younger males and associated with milder disease, whereas nonallergic asthma is more common in older females and more severe disease. Nonallergic asthma exacerbations are more commonly triggered by infection, irritants, gastroesophageal reflux disease, stress, and exercise. Despite the many overlapping phenotypes of asthma, the pattern of airway inflammation, the cellular profile, and the response of structural cells is consistent across all types of asthma.
The asthma phenotype can be quite variable because of complex interactions between the environment and underlying genetic factors. Although asthma symptoms are typically episodic and reversible (either spontaneously or with treatment), there are also more long-term changes to the asthmatic airway that can occur from inflammation. Multiple inflammatory cells and cytokines have been described in asthma pathogenesis, yet the mechanisms leading to the variability of disease phenotypes are still only partially understood.
The Unified Airway, Asthma, and the Otolaryngologist
The unified airway model suggests that inflammatory diseases of the upper and lower airways are interconnected because of shared epithelial lining and inflammatory mediators. Pseudostratified columnar epithelium is the mucosal lining in the middle ear, nasal cavity, sinuses, and the lower airway, and the inflammatory mediators in chronic disease of the upper and lower airways, such as rhinosinusitis and asthma, are frequently the same (interleukin [IL]-4, IL-5, and IL-13). Rhinitis, sinusitis, and asthma are frequently comorbid conditions. Indeed, a coincidence of upper and lower airway pathologies is suggested by self-reported symptoms in people with asthma, who list allergic rhinitis and sinusitis as their most common comorbidities. A study by Corren demonstrated the presence of rhinitis in 78% of people with asthma, and the presence of asthma in 38% of patients with rhinitis. Other conditions that otolaryngology patients frequently present with include vocal cord dysfunction, obstructive sleep apnea, and gastroesophageal reflux disease, all of which can masquerade as asthma, and can coexist with it. It is therefore important for otolaryngologists to be aware of the diagnosis and management of this common, complex, and treatable disease.
What is asthma?
Asthma is a chronic inflammatory disorder characterized by airway obstruction and hyperresponsiveness. The medical term “asthma,” which derives from the Greek for “panting,” was named by Hippocrates around 400 bc . Sir William Osler described asthma in his Principles and Practice of Medicine in the early 20th century as “swelling of the nasal or respiratory mucous membrane, increased secretion, and…spasm of the bronchial muscles with dyspnea, chiefly expiratory.” Of its treatment, he said, “Ordinary tobacco cigarettes are sometimes helpful.” (This position is no longer considered true.) Many decades later, it is now understood that asthma is a complex disease of airway inflammation characterized by airway edema, remodeling, and hyperresponsiveness. Asthma exacerbations are characterized by progressively worsening shortness of breath, cough, chest tightness, and/or wheezing. Under this umbrella of clinical symptoms, there is a very sophisticated interplay between underlying genotypes and environmental triggers that is only partially understood. This leads to a broad array of variable disease phenotypes and manifestations. Asthma is increasingly recognized as a syndrome, rather than an illness.
Diagnosis
The diagnosis of asthma is made when episodic symptoms of airflow obstruction or airway hyperresponsiveness are present, airflow obstruction is partially reversible, and alternative diagnoses are excluded. In addition to a good medical history and physical examination, spirometry is needed to demonstrate obstruction and assess reversibility. Reversibility is determined by an increase in forced expiratory volume in 1 second (FEV 1 ) of greater than or equal to 12% from baseline or an increase greater than or equal to 10% of predicted FEV 1 after inhalation of a short-acting β 2 -agonist. The National Institutes of Health Guidelines for the Diagnosis and Management of Asthma recommend considering a diagnosis of asthma when certain key indicators are present ( Table 1 ). The key indicators consist of specific symptoms, physical examination findings, and modifying factors and environmental exposures. There is a great deal of overlap between asthma symptoms and other disorders of the respiratory tract. The differential diagnosis for asthma symptoms includes allergic rhinitis or sinusitis, foreign body, aspiration, gastroesophageal reflux, laryngotracheomalacia, vocal cord dysfunction, bronchiolitis, chronic obstructive pulmonary disease, and cystic fibrosis, among other conditions. Recurrent cough and wheezing should always alert practitioners to the possibility of asthma.
| Symptoms | Physical Examination Findings | Modifying Factors |
|---|---|---|
| Wheezing (recurrent) Cough, worse at night Difficulty breathing (recurrent) Chest tightness (recurrent) | Thoracic hyperexpansion Wheezing during normal breathing Prolonged phase of forced exhalation Rhinorrhea Nasal polyps Atopic dermatitis | Exercise Viral infection Animals with fur or hair Dust mites Mold Smoke Pollen Changes in weather Airborne chemicals or dusts Menstrual cycles |
Asthma can be intermittent or persistent, and it can present with acute flares or chronic symptoms. Asthma severity is measured by objective measures of lung function (ie, spirometry or peak flow meter) and by symptoms. Measures of impairment include nighttime awakenings, need for short-acting bronchodilators, work or school days missed, ability to engage in normal daily activities, and quality of life assessments. The frequency of exacerbations in the population with asthma varies widely. Importantly, the severity of disease (as measured by frequency of nighttime awakenings, usage of short-acting β 2 -agonists, and interference with normal activity) does not correlate with the intensity of exacerbations. Indeed, severe, life-threatening exacerbations can occur even in people with intermittent or mild asthma when provoked by an exposure, such as a viral illness, irritant, or allergen. However, decreased FEV 1 in children demonstrates a strong association with the risk of asthma exacerbations. In terms of modifying factors, viral infections are the most common cause of asthma exacerbations.
There is a traditional division between allergic and nonallergic asthma. Allergic asthma is the subtype that accounts for approximately 50% to 80% of asthma cases, and is defined as asthma and positivity to skin prick test or specific IgE. Allergic asthma is more common in younger males and associated with milder disease, whereas nonallergic asthma is more common in older females and more severe disease. Nonallergic asthma exacerbations are more commonly triggered by infection, irritants, gastroesophageal reflux disease, stress, and exercise. Despite the many overlapping phenotypes of asthma, the pattern of airway inflammation, the cellular profile, and the response of structural cells is consistent across all types of asthma.
The asthma phenotype can be quite variable because of complex interactions between the environment and underlying genetic factors. Although asthma symptoms are typically episodic and reversible (either spontaneously or with treatment), there are also more long-term changes to the asthmatic airway that can occur from inflammation. Multiple inflammatory cells and cytokines have been described in asthma pathogenesis, yet the mechanisms leading to the variability of disease phenotypes are still only partially understood.
The Unified Airway, Asthma, and the Otolaryngologist
The unified airway model suggests that inflammatory diseases of the upper and lower airways are interconnected because of shared epithelial lining and inflammatory mediators. Pseudostratified columnar epithelium is the mucosal lining in the middle ear, nasal cavity, sinuses, and the lower airway, and the inflammatory mediators in chronic disease of the upper and lower airways, such as rhinosinusitis and asthma, are frequently the same (interleukin [IL]-4, IL-5, and IL-13). Rhinitis, sinusitis, and asthma are frequently comorbid conditions. Indeed, a coincidence of upper and lower airway pathologies is suggested by self-reported symptoms in people with asthma, who list allergic rhinitis and sinusitis as their most common comorbidities. A study by Corren demonstrated the presence of rhinitis in 78% of people with asthma, and the presence of asthma in 38% of patients with rhinitis. Other conditions that otolaryngology patients frequently present with include vocal cord dysfunction, obstructive sleep apnea, and gastroesophageal reflux disease, all of which can masquerade as asthma, and can coexist with it. It is therefore important for otolaryngologists to be aware of the diagnosis and management of this common, complex, and treatable disease.
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