What is aspiration pneumonia?

Aspiration Pneumonia

Aspiration pneumonia is defined as a pulmonary infection that occurs when material moves below the true vocal folds, enters the trachea, and causes inflammation in the lungs. 1

Definition and Pathophysiology

• Aspiration pneumonia occurs when material (food, liquids, oral secretions) passes below the true vocal folds into the trachea, resulting in a pulmonary infection 1
• It differs from penetration, which is when material enters the laryngeal area only to the level of the true vocal folds 1
• Aspiration pneumonia is the most common form of hospital-acquired pneumonia among adults, occurring in 4-8 of every 1,000 hospitalized patients 1
• Mortality rates for aspiration pneumonia range from 20% to 65%, highlighting its significant impact on patient outcomes 1

Risk Factors

Patient Populations at Highest Risk

• Stroke patients: 22-38% of acute stroke patients demonstrate aspiration on videofluoroscopic swallow evaluation (VSE) 1
• Elderly nursing home residents: Particularly those with:
  • Difficulty swallowing food (OR 2.0) 1
  • Use of sedative medications (OR 8.3) 1
  • Being fed by gastric tube (OR 3.03) 1
  • Requiring total assistance for oral care (OR 2.8) 1
• Post-cervical surgery patients: 42% of patients undergoing anterior cervical operations and 20% of those undergoing posterior cervical procedures 1
• Neonates and infants: Neonatal aspiration syndromes occur in 4% of all live births with significant mortality 1

Specific Risk Factors

• Dysphagia (abnormal swallowing due to impaired coordination, obstruction, or weakness) 1
• Decreased level of consciousness 1
• Impaired laryngeal sensation 1
• History of previous aspiration pneumonia (OR 7.00) 1
• Bed-bound status and reduced activity levels 1
• Dependence on others for feeding (OR 19.98) 1
• Current smoking (OR 4.13) 1
• Multiple medication use (>8 medications) (OR 1.15) 1
• Invasive procedures and presence of nasogastric tubes 1
• Insufficient oral care 1

Clinical Presentation and Diagnosis

• Typical presentation includes fever, cough, and auscultatory findings such as rales or evidence of pulmonary consolidation 1
• Chest radiograph typically shows infiltrates in dependent bronchopulmonary segments 2
• Aspiration can occur without coughing (silent aspiration), particularly in neonates and infants who may present with apnea and increased swallowing frequency instead 1
• Diagnostic clues include:
  • Prior episodes of coughing on food or liquid intake 3
  • History of relevant underlying conditions 3
  • Abnormalities on videofluoroscopy or water swallowing tests 3
  • Gravity-dependent shadow distribution on chest imaging 3

Microbiology

• In community-acquired aspiration pneumonia: Oral bacteria predominate, including:
  • Streptococcus pneumoniae 4
  • Haemophilus influenzae 4
  • Staphylococcus aureus 4
  • Anaerobic bacteria 4, 5
• In hospital-acquired or nursing home settings: Additional pathogens include:
  • Aerobic gram-negative bacilli (Klebsiella pneumoniae, Pseudomonas aeruginosa) 1, 5
  • Staphylococcus aureus 1, 5
• Anaerobic bacteria are found in over 90% of cases, including Bacteroides, Fusobacterium, Peptococcus, and Peptostreptococcus species 5

Treatment

Antibiotic Therapy

• For community-acquired aspiration pneumonia (admitted from home):
  • Oral or IV β-lactam/β-lactamase inhibitor
  • Clindamycin
  • IV cephalosporin + oral metronidazole
  • Moxifloxacin 1
• For ICU patients or those admitted from nursing homes:
  • Clindamycin + cephalosporin 1

Supportive Care

• Early mobilization for all patients 1
• Low molecular weight heparin for patients with acute respiratory failure 1
• Consider non-invasive ventilation, particularly in patients with COPD 1
• Corticosteroids may be considered for aspiration pneumonitis (non-infectious inflammation following aspiration of gastric contents) but are not routinely recommended for aspiration pneumonia 6, 2

Prevention Strategies

• Dysphagia screening and swallowing evaluation in high-risk patients 7
• Proper positioning during feeding (upright position) 7
• Thickened liquids for patients with swallowing difficulties 1
• Meticulous oral hygiene 1
• Minimizing sedative use in high-risk patients 1
• Patient and caregiver education on proper feeding techniques 7
• Early mobilization 1
• Removal of unnecessary tubes (nasogastric, etc.) when possible 7

Monitoring Response

• Monitor response to treatment using simple clinical criteria:
  • Body temperature
  • Respiratory parameters
  • Hemodynamic parameters 1
• C-reactive protein should be measured on days one and three/four, especially in patients with unfavorable clinical parameters 1
• Complete radiographic resolution may require longer time periods 1

Special Considerations

• In neonates and infants, aspiration may present with apnea rather than coughing, making detection more challenging 1
• Elderly patients with aspiration pneumonia tend to be frail with multiple comorbidities, requiring comprehensive care approaches 3
• Non-responding pneumonia should be fully reinvestigated, particularly in unstable patients 1