How to differentiate and manage bronchitis vs asthma exacerbation?

Differentiating and Managing Bronchitis vs Asthma Exacerbation

The critical first step is to rule out asthma as the cause of acute cough, as approximately one-third of patients initially diagnosed with acute bronchitis actually have acute asthma, and 65% of patients with recurrent "acute bronchitis" episodes have underlying mild asthma. 1

Key Diagnostic Distinctions

Clinical Features That Suggest Asthma Over Bronchitis

• History of recurrent episodes: If the patient has had at least two similar doctor-diagnosed episodes of "acute bronchitis" in the past 5 years, there is a 65% probability of underlying mild asthma 1
• Wheezing and dyspnea predominance: Asthma exacerbations present with progressively worsening shortness of breath, wheezing, and chest tightness, whereas acute bronchitis manifests predominantly as cough with or without sputum production 1
• Response pattern: Asthma symptoms characteristically worsen at night or with triggers (exercise, allergens, cold air), while bronchitis symptoms are more constant 1
• Duration: Acute bronchitis is self-limited and lasts no more than 3 weeks; if cough persists beyond 3 weeks, other diagnoses including asthma must be considered 1

Objective Assessment

Spirometry or peak expiratory flow (PEF) measurement is essential to differentiate these conditions, as objective measures of lung function are more reliable than symptoms alone 1:

• Reversible airflow obstruction: A bronchodilator response showing ≥12% and ≥200 mL improvement in FEV1, or ≥20% improvement in PEF, indicates asthma 1
• Normal baseline spirometry does not exclude asthma: If FEV1 is ≥70% predicted and clinical suspicion remains high, bronchial provocation testing should be performed 1
• Chest radiograph: Essential to rule out pneumonia, which fundamentally changes management; the absence of infiltrate supports bronchitis diagnosis 1, 2

Critical Pitfall to Avoid

Do not assume purulent (whitish, green, or yellow) sputum indicates bacterial infection requiring antibiotics—sputum color does not reliably differentiate bacterial from viral lower respiratory tract infections 2, 3

Management Algorithm

For Confirmed Acute Bronchitis (After Excluding Asthma and Pneumonia)

Routine antibiotic therapy is NOT indicated and should not be offered, as viruses cause more than 90% of acute bronchitis cases 1, 3:

• No routine antibiotics: Antibiotics should only be considered if the condition worsens and a complicating bacterial infection is suspected, or if pertussis is confirmed 1
• No routine bronchodilators: Inhaled beta-agonists, anticholinergics, and corticosteroids have not been shown to be effective for acute bronchitis 1
• Symptomatic treatment only: Antitussive agents may provide short-term symptomatic relief 1
• Reassessment: If cough persists beyond 3 weeks or worsens, targeted investigations including chest x-ray, spirometry, and consideration of asthma should be pursued 1

For Confirmed Asthma Exacerbation

Classify severity immediately using objective lung function measures (FEV1 or PEF percent predicted), as this determines treatment intensity 1:

Mild-to-Moderate Exacerbation (FEV1 or PEF >40% predicted)

• Short-acting beta-2 agonist (SABA): 2-4 puffs every 20 minutes for first hour 1
• For patients on ICS-formoterol maintenance: Additional 1-2 inhalations of budesonide-formoterol (160/4.5 μg) may be taken, not exceeding 8 inhalations daily 4
• Oral corticosteroids: Add prednisone 40-60 mg daily for 5-7 days if inadequate response to bronchodilators 1

Severe Exacerbation (FEV1 or PEF ≤40% predicted)

• Immediate high-dose SABA: Via nebulizer or metered-dose inhaler with spacer 1
• Systemic corticosteroids: Prednisone 40-60 mg orally or equivalent IV immediately 1, 5
• Oxygen: To maintain SpO2 ≥90% 1
• Consider ED transfer or hospitalization: Especially if risk factors for asthma-related death are present 1

Risk Factors Requiring Heightened Vigilance

Patients with the following are at high risk for asthma-related death and require intensive monitoring 1:

• Previous severe exacerbation requiring intubation or ICU admission
• Two or more hospitalizations or three or more ED visits for asthma in the past year
• Using more than 2 canisters of SABA per month
• Difficulty perceiving airway obstruction severity
• Low socioeconomic status, illicit drug use, or major psychiatric problems

When Diagnosis Remains Uncertain

If clinical features overlap and spirometry is unavailable or non-diagnostic, initiate empiric asthma therapy 1:

• Start with low-dose ICS-LABA combination therapy 1
• Reassess in 2-4 weeks with objective lung function testing 1
• If symptoms resolve completely with ICS therapy and recur when stopped, asthma is confirmed 1
• If no response after 4-6 weeks of adequate ICS therapy, reconsider the diagnosis 1

The key principle: treat what you can prove, and prove what you suspect through therapeutic trials with objective monitoring.