Aspiration Pneumonia and Pneumonitis
Lung injury from inhaled oropharyngeal or gastric contents — chemical vs infectious.
Also known as: aspiration pneumonia, aspiration pneumonitis, Mendelson syndrome, anaerobic pneumonia
Overview
Aspiration pneumonitis: acute lung injury after inhalation of sterile gastric contents (chemical). Aspiration pneumonia: infectious pneumonia from aspirated oropharyngeal flora colonizing distal airways.
Epidemiology
Common in elderly, stroke patients, and those with neurologic disease. Accounts for ~10% of CAP in older adults. Increased in nursing home residents, post-operative patients, and those with dysphagia.
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Risk factors
- Altered mental status: stroke, dementia, intoxication, anesthesia, seizure, head injury
- Dysphagia: stroke, Parkinson disease, neuromuscular disease, esophageal disorders, head and neck cancer
- Mechanical: NG tube, endotracheal tube, tracheostomy, vomiting
- GERD, gastroparesis, bowel obstruction
- Poor dentition, periodontal disease (anaerobic load)
- Recumbent feeding
Pathophysiology
Chemical pneumonitis: aspirated gastric acid (pH <2.5) damages alveolar epithelium → rapid-onset inflammation, edema, hypoxemia. Aspiration pneumonia: bacterial colonization of aspirated material leads to infection over 24-72 h. Predominantly dependent lung segments — superior segment of lower lobes (supine) or posterior segment of upper lobes/RML (lateral recumbent). Microbiology: streptococci, S. aureus, gram-negatives, and anaerobes; anaerobic role has been overstated.
Clinical presentation
Symptoms
- Witnessed aspiration event, choking, or coughing during meals
- Cough (may be productive), dyspnea, wheeze
- Chemical pneumonitis: acute respiratory distress within minutes-hours of aspiration
- Pneumonia: subacute fever, productive cough, foul-smelling sputum (especially with anaerobes/abscess)
Signs / physical exam
- Tachypnea, hypoxia, fever
- Crackles or bronchial breath sounds in dependent segments
- Halitosis with anaerobic infection or abscess
Classic findings
Infiltrate in posterior segment of upper lobe or superior segment of lower lobe (supine aspiration); right side more common (more vertical right main bronchus).
Differential diagnosis
- Community-acquired pneumonia — No witnessed aspiration; non-dependent distribution; typical pathogens
- Lung abscess — Cavitary lesion with air-fluid level, foul-smelling sputum, indolent course over weeks
- Pulmonary edema — Bilateral perihilar pattern, elevated BNP, responds to diuresis
- Pulmonary embolism — Acute pleuritic pain, hypoxia, VTE risk factors; CTPA
- ARDS from non-aspiration cause — Sepsis, trauma, pancreatitis — bilateral infiltrates, PaO2/FiO2 ≤300
- Foreign body aspiration — Sudden choking episode; focal hyperinflation or atelectasis; bronchoscopy diagnostic and therapeutic
- Exogenous lipoid pneumonia — History of mineral oil ingestion or vaping; low attenuation on CT
Diagnostic workup
Labs
- CBC, BMP, lactate, blood cultures (if pneumonia)
- Sputum Gram stain/culture; anaerobic culture rarely useful given oropharyngeal contamination
Imaging
- CXR — infiltrate in gravity-dependent segments; bilateral if large volume
- CT chest if abscess, empyema, or non-resolution; identifies cavitation, foreign body
- Bronchoscopy if obstructing foreign body suspected
Other studies
- Swallow evaluation (video fluoroscopic swallow study or fiberoptic endoscopic evaluation of swallowing) after stabilization, especially post-stroke
- Modified barium swallow to characterize aspiration risk and guide dietary/feeding strategy
Diagnostic algorithm
| Feature | Pneumonitis (Chemical) | Pneumonia (Infectious) |
|---|---|---|
| Time course | Minutes-hours | Days |
| Cause | Sterile gastric acid | Oropharyngeal bacteria |
| Sputum | Frothy, non-purulent | Purulent, ± foul-smelling |
| Resolution | 24-48 h with support | Requires antibiotics × 5-7 days |
| Antibiotics | Usually not needed | Beta-lactam ± anaerobic coverage if abscess |
Treatment
First-line
- Aspiration pneumonitis (chemical, witnessed, no infection signs): supportive care — supplemental O2, suctioning, observation. Do NOT routinely give antibiotics; many resolve in 24-48 h.
- Aspiration pneumonia (community-onset, non-severe): ampicillin-sulbactam 1.5-3 g IV q6h OR amoxicillin-clavulanate 875 mg PO BID; alternative: respiratory fluoroquinolone (moxifloxacin) or doxycycline
- Severe community aspiration pneumonia: piperacillin-tazobactam or ceftriaxone + metronidazole (if severe periodontal disease or putrid sputum); add MRSA coverage if risk factors
- Hospital-acquired aspiration: cover MRSA + Pseudomonas as for HAP/VAP — piperacillin-tazobactam, cefepime, meropenem ± vancomycin/linezolid
- Persuasive recent data: routine anaerobic coverage often unnecessary unless lung abscess, empyema, necrotizing pneumonia, or severe periodontal disease
Second-line / adjunct
- Lung abscess: prolonged antibiotics 3-6 weeks until cavity resolves or stable scar; surgical/percutaneous drainage if no response after 4-6 weeks
- Empyema or complicated parapneumonic effusion: chest tube ± intrapleural tPA/DNase
- Address underlying aspiration risk: speech-language pathology, diet modification, swallow rehab, elevation of head of bed, dental care, reflux management
- Tube feeding (PEG, NG) does NOT reliably prevent aspiration in advanced dementia
Complications
- Lung abscess, empyema
- ARDS, respiratory failure
- Recurrent aspiration, chronic pneumonitis
- Bronchiectasis from repeated injury
- Bronchopleural fistula, necrotizing pneumonia
PANCE pearls
- Distinguishing pneumonitis (chemical, 24-h resolution) from pneumonia (bacterial, persistent) determines whether antibiotics are needed.
- Right lower lobe (especially superior segment) and right middle lobe are favored sites due to bronchial anatomy in supine patients.
- Modern data downplay routine anaerobic coverage — reserve clindamycin or metronidazole add-on for clear abscess, empyema, putrid sputum, or severe periodontal disease.
- PEG tube placement does not reduce aspiration pneumonia or mortality in advanced dementia.
- Following a stroke, a formal swallow evaluation before any oral intake reduces pneumonia incidence.
References
- ATS/IDSA 2019 CAP — Diagnosis and Treatment of Adults with Community-acquired Pneumonia (Metlay et al., Am J Respir Crit Care Med 2019)
- NEJM Review — Aspiration Pneumonitis and Aspiration Pneumonia (Marik, NEJM 2001)
- Stroke Guideline — 2018 Guidelines for the Early Management of Patients with Acute Ischemic Stroke (Powers et al., Stroke 2018) — dysphagia screening
- Bartlett — Anaerobic Bacterial Infections of the Lung and Pleural Space (Bartlett, Clin Infect Dis 1993)
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