Aspiration pneumonia and pneumonitis


  • Difficult to predict which patients with pneumonitis will go on to develop pneumonia, aspiration alone does not cause pneumonia
  • Witnessed aspiration key to distinguishing between the two
  • Aspiration pneumonitis
    • Inflammatory chemical injury of tracheobronchial tree and pulmonary parenchyma
    • Due to inhalation of regurgitated sterile gastric contents
    • Must aspirate at least 20-30mL of gastric contents with pH <2.5
    • Can lead to aspiration pneumonia due to pulmonary defense mechanism injury
  • Aspiration pneumonia
    • Alveolar space infection secondary to inhalation of pathogenic material from oropharynx
    • Result of a complex interplay of the aspirated material, aspirated volume, pH, patient physiology and pulmonary defense mechanisms
    • Increased in patients with periodontal disease, chronic colonization of upper airways, or taking PPI/H2-blockers
    • Accounts for up to 20% of community-acquired pneumonia in elderly, majority of nursing home-acquired pneumonia
    • Microbiology

Risk factors

  • Advanced age
  • Altered level of consciousness
  • Anatomic abnormality of upper airway
  • Dementia
  • Esophageal disorders
  • Gastroesophageal reflux
  • Neuromuscular disease
  • Poor oral hygiene
  • Prior history of aspiration
  • Prolonged supine position
  • Retained gastric material
  • Tube feedings

Clinical Features

  • Aspiration pneumonia
  • Aspiration pneumonitis
    • Cough
    • Bronchospasm
    • Tachypnea
    • Bloody sputum
    • Low-grade fever
    • Respiratory distress

Differential Diagnosis

Acute dyspnea





  • CXR
    • Unilateral focal or patchy consolidations in dependent lung segments
    • Right lower lobe is most common area; bilateral patterns can also be seen
    • Lower lobe infiltrate when aspiration occurs in upright position
    • Upper lobe infiltrate when aspiration occurs in recumbent position
  • CT
    • Increased sensitivity, specificity, and overall accuracy compared to CXR
    • Reasonable to obtain even if CXR negative if clinical suspicion is high
    • Aspiration is a risk factor for pulmonary abscess formation


  • Aspiration pneumonitis
  • Aspiration pneumonia
    • Community-acquired
    • Health care-associated or periodontal disease or alcoholism
      • Ceftriaxone + clindamycin OR
      • Piperacillin-tazobactam + clindamycin OR
      • Ampicillin-sulbactam + clindamycin OR
      • Cefepime + clindamycin OR
      • Levofloxacin + clindamycin


  • Admit all patients with aspiration pneumonia
  • For aspiration pneumonitis, consider discharge if:
    • Otherwise healthy and non-toxic
    • Give outpatient antibiotics if symptomatic for >48hrs
  • For aspiration pneumonitis, consider admission for:
    • Chronically ill or immunocompromised
    • Nursing home patient

See Also

  • Pneumonia (Main)


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