Etymology

• Derived from the Latin word aspirare, meaning “to breathe in or draw in.”

AKA

• Pulmonary aspiration

Definition

What is it?

• • Lung aspiration refers to the entry of foreign material, such as food, liquid, saliva, or gastric contents, into the trachea and lungs, bypassing the protective mechanisms of the upper airway.

Caused by:

• • Impaired swallowing (dysphagia) due to neurologic disorders (e.g., stroke, Parkinson’s disease).
  • Gastroesophageal reflux disease (GERD) with regurgitation.
  • Altered consciousness due to sedation, anesthesia, or alcohol intoxication.
  • Mechanical disruption of airway protective mechanisms, such as endotracheal intubation.

Resulting in:

• • Inflammatory response within the lungs, which may cause:
    • Aspiration pneumonitis (chemical injury from gastric acid).
    • Aspiration pneumonia (infectious response to aspirated material).
  • Obstruction of the airway by aspirated particulate material.

Structural Changes:

• • Localized or diffuse inflammation of the lung parenchyma.
  • Alveolar damage due to chemical or infectious processes.
  • Bronchial obstruction from particulate matter.

Pathophysiology:

• • Aspiration triggers a local inflammatory response in the airways and alveoli.
  • The severity depends on the type and volume of aspirated material:
    • Gastric acid: Causes chemical pneumonitis through tissue injury and alveolar capillary leakage.
    • Particulate material: Can obstruct airways and lead to atelectasis or secondary infection.
    • Oral or gastric flora: May result in infectious pneumonia, particularly in dependent lung segments.
  • Aspiration occurs more frequently in the right lower lobe due to the steeper angle of the right mainstem bronchus.

Pathology:

• • Necrotizing inflammation in aspiration pneumonia.
  • Chemical burns and alveolar exudation in aspiration pneumonitis.
  • Evidence of particulate material in bronchi and alveoli.

Diagnosis

Clinical:

• • • Sudden onset of cough, dyspnea, or hypoxemia after a choking episode.
    • Fever, leukocytosis, and purulent sputum in aspiration pneumonia.
    • Risk factors such as neurologic impairment, GERD, or altered consciousness.

Radiology:

• • • CXR:
      • Consolidation in dependent lung segments (e.g., posterior segments of the upper lobes, superior segments of the lower lobes).
    • CT:
      • Ground-glass opacities or consolidation in aspiration pneumonitis.
      • Localized or multifocal consolidation in aspiration pneumonia.

Labs:

• • • Elevated white blood cell count in aspiration pneumonia.
    • Blood cultures or sputum cultures to identify causative organisms.

Treatment

• • • Aspiration pneumonitis: Supportive care, including oxygen therapy and bronchodilators if bronchospasm occurs. Antibiotics are not typically required unless secondary infection develops.
    • Aspiration pneumonia: Antibiotic therapy targeting anaerobes and polymicrobial infections (e.g., clindamycin, amoxicillin-clavulanate).
    • Prevention strategies, including head elevation, swallowing therapy, and minimizing sedative use.

Radiology in Detail

CXR

Findings:

• • Consolidation in dependent lung segments.
  • Possible atelectasis or airspace opacities.

Associated Findings:

• • Evidence of prior aspiration events, such as recurrent consolidations or bronchiectasis.

CT

Parts:

• • • Dependent lung segments, especially the right lower lobe.

Size:

• • • Variable, depending on the volume of aspirated material and the extent of the inflammatory response.

Shape:

• • • Consolidations may appear wedge-shaped or lobular.

Position:

• • • Most commonly in the right lower lobe, posterior segments of the upper lobes, or superior segments of the lower lobes due to gravity.

Character:

• • • Ground-glass opacities in pneumonitis.
    • Dense consolidations with air bronchograms in pneumonia.

Time:

• • • Onset can be acute in aspiration pneumonitis, with findings resolving over days.
    • Aspiration pneumonia may have a more prolonged course with progressive findings over days to weeks.

Associated Findings:

• • • Bronchiectasis or cavitation in chronic aspiration-related infections.

Other Imaging Modalities

• Modified barium swallow (MBS) and esophagram play critical roles in evaluating aspiration.
• The MBS, performed under fluoroscopy,
  • assesses oropharyngeal swallowing mechanics,
  • identifying dysfunctions such as
    • impaired epiglottic closure or
    • laryngeal aspiration.
  • It is particularly useful in patients with neurologic disorders or after head and neck surgery.
• The esophagram, also performed under fluoroscopy, evaluates the esophagus for structural abnormalities (e.g., strictures, diverticula) or motility disorders (e.g., achalasia, GERD) that can predispose to aspiration.
• Together, these studies provide dynamic and structural insights, guiding tailored interventions like swallowing therapy, dietary modifications, or surgical management to minimize aspiration risks.

Key Points and Pearls

• Aspiration is common in patients with altered airway protection, such as neurologic impairment or sedation.
• Radiological findings are gravity-dependent, with the right lower lobe being most frequently involved.
• Aspiration pneumonitis is a chemical injury, while aspiration pneumonia is an infection, requiring antibiotics.
• Prevention strategies are critical in at-risk patients to minimize recurrent aspiration events.