Asthma Definition and Characteristics

Definition and Characteristics of Asthma

• Asthma is a heterogeneous disease characterized by chronic airway inflammation and variable respiratory symptoms.
• Symptoms include wheeze, shortness of breath, chest tightness, and cough, which vary over time and intensity.
• Asthma is defined by a history of these symptoms, along with variable expiratory airflow limitation.

Risk Factors

• Allergy
• Genetic predisposition
• Smoking
• Obesity

Pathogenesis

• Airway hyperreactivity, resulting in airway narrowing as a reaction to irritants.
• Inflammation and airway remodeling, including eosinophilic inflammation.

Classification

• T2-type asthma: allergic and late onset eosinophilic asthma, exercise-induced asthma, and childhood or early adulthood onset.
• Non-T2 type asthma: obesity associated asthma, smooth muscle mediated paucigranulocytic asthma, and smoking related neutrophilic asthma.

Phenotypes

• Allergic asthma
• Non-allergic asthma
• Late-onset asthma
• Asthma with persistent/fixed airway obstruction (non-reversible)

Clinical Signs and Symptoms

• Wheezing
• Cough
• Dyspnea
• Symptoms usually worsen in mornings
• Night asthma
• Can develop in any age, but less frequent in older adults
• 75% of cases are diagnosed before age 7

Diagnosis

• Objective examination: usually normal, with wheezing (also common in respiratory infections, COPD, upper airway dysfunction, and heart failure)
• Anamnesis: symptoms change over time and intensity, worsen at night or when waking up, and can be provoked by exercise, laughter, allergens, or cold air
• Tests: spirometry, challenge test, and exercise challenge test

Control of Asthma

• Assessment based on symptoms in the past 4 weeks
• Well-controlled: no symptoms or need for reliever
• Partially controlled: 1-2 symptoms or need for reliever
• Uncontrolled: 3-4 symptoms or need for reliever

Severity Assessment

• Mild asthma: can be controlled with treatment in step 1 or 2
• Moderate asthma: can be controlled with treatment in step 3
• Severe asthma: can be controlled with treatment in step 4 or 5, or remains uncontrolled

Management

• Step 1: for symptoms less than twice a month
• Step 1/2 track 1 or step 2 track 2: for symptoms less than 4-5 days a week
• Step 3: for symptoms most days, or waking with asthma once a week or more
• Step 4: for daily symptoms or waking with asthma once a week or more, and low lung function
• Non-pharmacological treatment includes avoidance of smoke, allergens, and occupational factors, as well as physical activity, breathing techniques, weight reduction, and stress reduction.