Upon completion of the chapter, the reader will be able to:
Describe the pathophysiology and clinical presentation of acute and chronic asthma.
List the treatment goals for asthma.
Identify environmental factors associated with worsening asthma control.
Select inhaled drug delivery devices based upon patient characteristics.
Evaluate current metered-dose inhaler technique.
Recommend a therapeutic plan based upon asthma control and severity.
Develop an individualized asthma action plan.
KEY CONCEPT Asthma is a complex disorder and has been defined as “a heterogeneous disease, usually characterized by chronic airway inflammation.”1 Airflow limitation results in wheezing, breathlessness, chest tightness, and coughing, particularly at night or early in the morning.1 Severity of chronic disease ranges from mild intermittent symptoms to a severe and disabling disease. Despite variability in the severity of chronic asthma, all patients with asthma are at risk of acute severe disease. International guidelines emphasize the importance of treating underlying airway inflammation to control asthma and reducing asthma-associated risks.1,2,3
EPIDEMIOLOGY AND ETIOLOGY
KEY CONCEPT Asthma is the most prevalent chronic disease of childhood, and it causes significant morbidity and mortality in both adults and children. About 235 million adults and children worldwide have asthma.4 In the United States, asthma affects 8% of adults (18.7 million) and 9.3% of children (6.8 million).5 Asthma is the primary diagnosis for 14.2 million physician office visits, 1.8 million emergency department visits, and 3345 deaths annually.5
Asthma is also a significant economic burden in the United States, with costs totaling nearly $60 billion annually.6 Prescription medications are the single largest direct medical expenditure and account for 71% of direct medical costs.6
Asthma results from a complex interaction of genetic and environmental factors. There appears to be an inherited component because the presence of asthma in a parent is a strong risk factor for developing asthma in a child. This risk increases when a family history of atopy is also present. The presence of atopy is a strong prognostic factor for continued asthma as an adult.
Environmental exposure also appears to be an important etiologic factor. Although asthma occurs early in life for most patients, those with occupational asthma develop the disease later upon exposure to specific allergens in the workplace. Exposure to secondhand smoke after birth increases the risk of childhood asthma.7 Adult-onset asthma may be related to atopy, nasal polyps, aspirin sensitivity, occupational exposure, or recurrence of childhood asthma.
KEY CONCEPT Asthma is characterized by airway narrowing and inflammation primarily in medium-sized bronchi. A key feature of the pathophysiology is airway hyperresponsiveness, which is exaggerated narrowing of the airways in response to a trigger or allergen such as cold air, strong odors, pollen, or ...