Is acute bronchitis considered an upper respiratory tract infection?

Acute Bronchitis: Lower Respiratory Tract Infection, Not Upper

Acute bronchitis is a lower respiratory tract infection, not an upper respiratory tract infection, as it involves inflammation of the bronchi in the lower respiratory tract rather than the upper airways.

Anatomical Classification and Definition

• Acute bronchitis is defined as an acute respiratory infection manifested by cough with or without sputum production lasting up to 3 weeks 1
• The condition involves inflammation of the trachea and major bronchi, which are part of the lower respiratory tract 1, 2
• The presumed lower airway cough of acute bronchitis is distinct from the upper airway cough syndrome associated with the common cold 1

Distinguishing Features Between Upper and Lower Respiratory Infections

• Upper respiratory tract infections primarily affect the nasal passages, pharynx, and larynx, presenting with nasal congestion, rhinorrhea, and pharyngitis 1
• Lower respiratory tract infections, including acute bronchitis, involve the trachea, bronchi, and lungs with symptoms such as cough, dyspnea, chest pain, and wheezing 1
• Signs suggestive of lower respiratory tract involvement include:
  • Cough (often productive)
  • Dyspnea
  • Chest pain
  • Wheezing
  • Diffuse or focal signs on auscultation 1

Diagnostic Considerations

• The diagnosis of acute bronchitis requires ruling out pneumonia, common cold, acute asthma, and COPD exacerbation 1
• Acute bronchitis is primarily caused by viral infections (>90% of cases), with bacteria such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Bordetella pertussis responsible in fewer than 10% of patients 1, 2
• Transient airflow obstruction and bronchial hyperresponsiveness can occur in approximately 40% of previously healthy individuals with acute bronchitis 1

Clinical Overlap and Diagnostic Challenges

• The clinical distinction between acute bronchitis and the common cold can be difficult as they share many symptoms 1
• Cough associated with the common cold is an upper airway cough syndrome often associated with throat clearing and postnasal drip 1
• The presumed lower airway cough of acute bronchitis may sometimes be accompanied by upper airway symptoms, further complicating diagnosis 1
• Asthma is commonly misdiagnosed as acute bronchitis in approximately one-third of patients presenting with acute cough 3

Treatment Implications

• Antibiotics are generally not indicated for acute bronchitis since it is primarily viral in origin 2
• Treatment should focus on symptom management rather than antimicrobial therapy 2
• The distinction between upper and lower respiratory infections is important for proper management and patient education 1

Common Pitfalls

• Misclassifying acute bronchitis as an upper respiratory tract infection may lead to inappropriate management strategies 1, 3
• Failing to recognize when "acute bronchitis" might actually be an early presentation of asthma or other chronic respiratory conditions 3
• Prescribing antibiotics unnecessarily based on patient expectations rather than clinical evidence 4
• Overlooking the possibility of pneumonia, which requires different management approaches 1