Definition of Bronchitis
Bronchitis is an inflammatory condition of the tracheobronchial tree that exists in two distinct forms: acute bronchitis (a self-limited respiratory infection lasting up to 3 weeks with cough as the predominant symptom) and chronic bronchitis (a disease manifested by cough and sputum expectoration occurring on most days for at least 3 months per year for at least 2 consecutive years when other causes are excluded). 1
Acute Bronchitis
Acute bronchitis is an acute respiratory infection manifested predominantly by cough, with or without phlegm production, that lasts for no more than 3 weeks. 1
Key Characteristics:
- Primarily a viral infection affecting previously healthy individuals, with respiratory viruses (adenovirus, rhinovirus, coronavirus, influenza, parainfluenza, respiratory syncytial virus) accounting for the majority of cases 1
- Atypical pathogens including Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella species are implicated in some cases 1
- Most common in winter months when acute respiratory infections are prevalent 1
- Accounts for more than 3 million outpatient office visits annually in the United States 2
Critical Diagnostic Distinction:
The diagnosis of acute bronchitis requires ruling out pneumonia (no infiltrate on chest radiograph), the common cold, acute asthma, and exacerbation of COPD as causes of acute cough. 1 This distinction is crucial because acute asthma is misdiagnosed as acute bronchitis in approximately one-third of patients presenting with acute cough 1
Chronic Bronchitis
Chronic bronchitis is defined as cough and sputum expectoration occurring on most days for at least 3 months of the year for at least 2 consecutive years when other pulmonary or cardiac causes for chronic productive cough are excluded. 1
Key Characteristics:
- Caused by prolonged exposure to pulmonary irritants, with cigarette smoke being the most prominent, along with atmospheric pollution and recurrent infections 1
- Results in chronic inflammation in the walls and lumen of the airways 1
- As disease advances, progressive airflow limitation occurs, usually in association with emphysema, leading to COPD 1
- Characterized as a "cough phlegm syndrome" with excessive mucous secretion in the bronchial tree 1
Acute Exacerbations:
Patients with chronic bronchitis frequently experience acute exacerbations superimposed on the chronic process, characterized by sudden clinical deterioration with increased sputum volume, sputum purulence, and/or worsening shortness of breath. 1
- Bacterial pathogens most commonly implicated include Streptococcus pneumoniae, Haemophilus influenzae (typable and nontypable), and Moraxella catarrhalis 1, 3
- Viruses are responsible for approximately one-third of acute exacerbations 3
- Pseudomonas aeruginosa is increasingly prevalent in patients with severe underlying disease 3
Common Diagnostic Pitfalls to Avoid:
- Do not confuse acute bronchitis with the common cold: The common cold presents primarily with nasal stuffiness, discharge, sneezing, and sore throat, whereas acute bronchitis manifests predominantly as cough 1
- Do not miss underlying asthma: In patients with recurrent "acute bronchitis" episodes (at least two in the past 5 years), 65% actually have mild asthma 1, 4
- Do not assume persistent cough beyond 3 weeks is still acute bronchitis: When cough persists beyond 3 weeks, other diagnoses including postinfectious cough, upper airway cough syndrome, asthma, and gastroesophageal reflux disease must be considered 1, 5
- Do not diagnose chronic bronchitis without meeting the temporal criteria: The diagnosis requires symptoms for at least 3 months per year for at least 2 consecutive years 1