Asthma — Stepwise Therapy and Acute Management

Asthma is a chronic inflammatory airway disease characterized by reversible airway obstruction, bronchial hyperresponsiveness, and underlying inflammation. [KEY_CONCEPT] The condition affects over 300 million people worldwide and is the most common chronic respiratory disease in children.

Pathophysiology

Asthma involves complex interactions between genetic predisposition, environmental triggers, and immune system dysfunction. The pathophysiology includes:

Inflammatory Cascade

• Type 2 helper T-cell (Th2) response: Release of IL-4, IL-5, and IL-13
• Eosinophilic inflammation: Recruited by IL-5, causing tissue damage
• Mast cell degranulation: Release of histamine, leukotrienes, and prostaglandins
• IgE-mediated hypersensitivity: Allergen-specific IgE binding to mast cells

Structural Changes

• Airway remodeling: Smooth muscle hypertrophy, subepithelial fibrosis
• Mucus hypersecretion: Goblet cell hyperplasia
• Bronchial hyperresponsiveness: Exaggerated response to stimuli

[CLINICAL_PEARL] The "asthma triad" consists of reversible airway obstruction, bronchial hyperresponsiveness, and chronic airway inflammation - all three components must be present for optimal control.

Phenotypes

Modern asthma management recognizes distinct phenotypes:

• Allergic asthma: IgE-mediated, early onset, good steroid response
• Non-allergic asthma: Late onset, often associated with nasal polyps
• Exercise-induced bronchospasm: Triggered by physical activity
• Occupational asthma: Workplace exposure-related

[HIGH_YIELD] Understanding asthma phenotypes is crucial for personalized therapy selection and predicting treatment response.

Classic Symptoms

Asthma presents with variable and reversible respiratory symptoms:

• Dyspnea: Often described as "chest tightness"
• Wheezing: Expiratory wheeze, may be absent in severe cases
• Cough: Often dry, worse at night or early morning
• Chest tightness: Sensation of constriction

[CLINICAL_PEARL] The absence of wheezing does not rule out asthma - severe bronchospasm may be too tight to produce audible wheeze ("silent chest").

Physical Examination Findings

Stable Asthma

• Often normal between exacerbations
• Possible expiratory wheeze
• Prolonged expiratory phase
• Signs of allergic disease (eczema, allergic rhinitis)

Acute Exacerbation Signs

Triggers and Patterns

[HIGH_YIELD] Common asthma triggers include:

• Allergens: Dust mites, pollens, pet dander, mold
• Irritants: Smoke, perfumes, strong odors, air pollution
• Respiratory infections: Viral upper respiratory infections
• Weather changes: Cold air, humidity changes
• Exercise: Especially in cold, dry conditions
• Medications: Beta-blockers, NSAIDs, ACE inhibitors
• Emotional stress: Can trigger bronchospasm

Symptom Patterns

• Diurnal variation: Symptoms often worse at night/early morning
• Seasonal patterns: May correlate with allergen exposure
• Exercise relationship: Symptoms during or after physical activity

[KEY_CONCEPT] Variability and reversibility of symptoms are hallmarks of asthma diagnosis.

Diagnostic Criteria

Asthma diagnosis requires demonstration of variable airway obstruction plus compatible clinical history:

Spirometry Criteria (GINA Guidelines)

DIAGNOSTIC ALGORITHM:

1. Clinical suspicion (symptoms + triggers) ↓
2. Pre-bronchodilator spirometry ↓
3. Bronchodilator reversibility test ↓
4. If normal: Consider alternative tests
   • Methacholine challenge
   • Exercise testing
   • Peak flow variability

Bronchodilator Reversibility

[HIGH_YIELD] Positive test criteria:

• FEV1 increase ≥12% AND ≥200 mL from baseline
• Measured 15-20 minutes after 400 mcg albuterol

Alternative Diagnostic Tests

When spirometry is normal or inconclusive:

• Methacholine challenge: PC20 <16 mg/mL suggests asthma
• Exercise stress test: >10% FEV1 drop post-exercise
• Peak flow monitoring: >20% diurnal variation over 2 weeks
• Fractional exhaled nitric oxide (FeNO): >50 ppb supports diagnosis

Laboratory Studies

• Complete blood count: Eosinophilia may suggest allergic asthma
• Total IgE and specific IgE: Identify allergic triggers
• Aspergillus-specific IgG/IgE: Rule out ABPA
• Vitamin D level: Deficiency associated with poor control

Differential Diagnosis

[CLINICAL_PEARL] In patients >40 years with smoking history, consider asthma-COPD overlap syndrome (ACOS) if significant reversibility is present.

[KEY_CONCEPT] Asthma diagnosis is clinical - no single test is definitive, and normal spirometry doesn't exclude the diagnosis.

GINA Step-Up Approach

Asthma management follows a stepwise approach based on symptom control and exacerbation risk:

STEPWISE THERAPY ALGORITHM:

Step 1: As-needed SABA ↓ (if inadequate control) Step 2: Low-dose ICS + as-needed SABA ↓ (if inadequate control) Step 3: Low-dose ICS/LABA combination ↓ (if inadequate control) Step 4: Medium/High-dose ICS/LABA ↓ (if inadequate control) Step 5: Add-on therapies:

• Tiotropium
• Anti-IgE (omalizumab)
• Anti-IL5 (mepolizumab)
• Oral corticosteroids

Step-by-Step Therapy Details

Step 1: Mild Intermittent

• As-needed short-acting beta-agonist (SABA)
• Albuterol 2 puffs every 4-6 hours as needed
• [HIGH_YIELD] SABA use >2 times/week indicates need for step-up

Step 2: Mild Persistent

• Low-dose inhaled corticosteroid (ICS) daily
• Plus as-needed SABA
• Examples: Fluticasone 88 mcg BID, Budesonide 180 mcg BID

Step 3: Moderate Persistent

• Low-dose ICS/LABA combination
• Examples: Fluticasone/salmeterol 100/25 mcg BID
• Alternative: Medium-dose ICS monotherapy

Step 4: Moderate-Severe Persistent

• Medium to high-dose ICS/LABA combination
• Consider add-on therapies if poor control

Step 5: Severe Persistent

• High-dose ICS/LABA plus:
• Tiotropium (long-acting antimuscarinic)
• Biological therapy for severe allergic/eosinophilic asthma
• Oral corticosteroids (lowest effective dose)

Controller Medication Classes

[CLINICAL_PEARL] ICS/LABA combinations are preferred over increasing ICS dose alone for step 3-4 therapy due to superior efficacy and reduced side effects.

Assessment of Control

Well-controlled asthma criteria:

• Daytime symptoms ≤2 times/week
• No nighttime awakening
• SABA use ≤2 times/week
• No activity limitation
• FEV1 >80% predicted
• No exacerbations

[KEY_CONCEPT] Step-down therapy should be attempted every 3 months in well-controlled patients to find the minimal effective dose.

Emergency Department Assessment

Rapid Triage Criteria

ACUTE ASTHMA SEVERITY ASSESSMENT:

IMMEDIATE (Life-threatening):

• Silent chest or minimal wheeze
• Unable to speak
• Cyanosis
• Altered consciousness
• Peak flow <25% predicted → Immediate aggressive treatment

URGENT (Severe):

• Speaks in single words
• Use of accessory muscles
• Peak flow 25-50% predicted → High-dose bronchodilators + steroids

LESS URGENT (Moderate):

• Speaks in phrases
• Some dyspnea
• Peak flow 50-75% predicted → Standard bronchodilator treatment

Acute Treatment Protocol

First-Line Therapy

1. High-dose SABA: Albuterol 2.5-5 mg nebulized every 20 minutes × 3
2. Systemic corticosteroids: Prednisone 40-80 mg PO or methylprednisolone 80-125 mg IV
3. Ipratropium bromide: 0.5 mg nebulized with albuterol (first 3 doses)

[HIGH_YIELD] Corticosteroids should be given within 1 hour of presentation and continued for 5-7 days for most exacerbations.

Severe/Life-threatening Exacerbations

Additional interventions:

• Continuous albuterol: 10-15 mg/hour nebulized
• Magnesium sulfate: 2 g IV over 20 minutes
• High-flow oxygen: Target SpO2 94-98%
• Consider intubation if:
  • Respiratory arrest
  • Altered mental status
  • Inability to maintain oxygenation

Refractory Cases

• Heliox: Helium-oxygen mixture (70:30 or 80:20)
• Ketamine: 0.2 mg/kg/hour IV (bronchodilator properties)
• Extracorporeal support: ECMO in extreme cases

Disposition Criteria

Discharge Home Criteria

• Peak flow >70% predicted or personal best
• Normal oxygen saturation on room air
• Minimal symptoms at rest
• Response sustained for 60 minutes after last treatment
• Adequate home medications and follow-up arranged

Hospital Admission Criteria

• Peak flow <50% predicted after treatment
• Persistent hypoxemia
• History of severe exacerbations/ICU admissions
• Inability to manage at home
• High-risk social factors

ICU Admission Criteria

• Respiratory failure: PCO2 >45 mmHg or rising
• Altered mental status
• Hemodynamic instability
• Need for intubation

[CLINICAL_PEARL] A normal or elevated PCO2 in acute asthma indicates impending respiratory failure due to severe obstruction and fatigue.

Post-Acute Care

• Prednisone taper: 40-60 mg daily × 5-7 days (no taper needed for short courses)
• Controller therapy: Initiate or step-up based on severity
• Action plan: Written instructions for future exacerbations
• Follow-up: Within 1-4 weeks with primary care or pulmonology

Acute Complications

Status Asthmaticus

Definition: Severe asthma exacerbation refractory to standard bronchodilator therapy

Clinical features:

• Duration >24 hours despite treatment
• Progressive respiratory failure
• Risk of ventilatory failure and death

Management:

• Aggressive bronchodilator therapy
• High-dose systemic corticosteroids
• Consider mechanical ventilation with lung-protective strategies

Pneumothorax

• Incidence: 1% of acute exacerbations
• Presentation: Sudden chest pain, increased dyspnea
• Management: Chest tube if >20% or tension pneumothorax

[HIGH_YIELD] Pneumomediastinum can occur from severe bronchospasm and increased intrathoracic pressure - usually self-limiting.

Chronic Complications

Airway Remodeling

• Subepithelial fibrosis: Irreversible airway narrowing
• Smooth muscle hypertrophy: Decreased bronchodilator response
• Prevention: Early, consistent anti-inflammatory therapy

Medication-Related Complications

[CLINICAL_PEARL] Spacer devices with MDIs reduce oral thrush risk and improve drug delivery by up to 40%.

Special Populations

Pregnancy

• Goal: Maintain optimal control to prevent maternal/fetal complications
• Safe medications: Albuterol, budesonide (preferred ICS)
• Avoid: Epinephrine, iodides
• Monitoring: Serial peak flows, fetal growth

Elderly Patients

• Challenges: Comorbidities, polypharmacy, device use
• Considerations: Drug interactions, cognitive function
• Common mistake: Underdiagnosis due to attribution to "aging"

Exercise-Induced Bronchospasm (EIB)

• Prevalence: 90% of asthmatics, 10% of general population
• Pathophysiology: Airway cooling and drying
• Prevention:
  • SABA 15 minutes before exercise
  • Adequate warm-up
  • Face mask in cold weather
• Long-term control: Daily ICS if frequent episodes

Quality of Life Impact

Psychosocial considerations:

• School/work absenteeism: Leading cause of missed school days
• Sleep disruption: Nocturnal symptoms affect 75% of patients
• Anxiety/depression: Higher prevalence in asthma patients
• Activity limitation: Fear of triggering symptoms

[KEY_CONCEPT] Asthma control encompasses not just physiologic parameters but also quality of life, functional capacity, and psychosocial well-being.