Uncategorized

• Etymology:
  Derived from “emphysema,” meaning “inflation” or “swelling.” Refers to air abnormally located within interstitial tissues of the lung.
• AKA:
  Pulmonary Interstitial Emphysema (PIE).
• What is it?
  Interstitial emphysema is the presence of air within the interstitial tissues of the lung, including the connective tissue, perivascular, or peribronchial regions.
• Caused by:
  1. Mechanical trauma: Overdistension of alveoli leading to rupture, commonly due to:
     • Barotrauma from positive-pressure ventilation.
     • Pulmonary contusion.
  2. Infection: Rare, associated with necrotizing infections causing alveolar rupture.
  3. Inflammation/immune: Rare, in settings like eosinophilic lung disease.
  4. Neoplasm: Air entrapment secondary to obstruction or compression by tumor.
  5. Metabolic: Rarely associated with metabolic diseases causing fragility of connective tissue.
  6. Circulatory: Rare, in cases of pulmonary embolism with associated alveolar damage.
  7. Inherited: Rare, seen in congenital conditions like alveolar capillary dysplasia.
  8. Congenital: More common in neonates with surfactant deficiency or structural immaturity.
  9. Other: Idiopathic cases are rare but reported.
• Resulting in:
  • Air tracking into interstitial spaces, leading to potential compression of airways or vasculature.
  • Impaired gas exchange and respiratory mechanics.
• Structural changes:
  • Alveolar rupture with air leakage into interstitial tissues.
  • Compression of adjacent lung structures.
  • Potential pneumothorax or pneumomediastinum.
• Pathophysiology:
  • Increased alveolar pressure causes rupture.
  • Air escapes into interstitial tissues, spreading along peribronchial and vascular sheaths.
  • May lead to subcutaneous emphysema or air embolism if severe.
• Pathology:
  • Gross: Air pockets visible in connective tissue.
  • Microscopic: Air-filled spaces in perivascular and peribronchial tissues.
• Diagnosis:
  • Clinical assessment, radiological findings, and exclusion of other causes of dyspnea or chest pain.
• Clinical:
  • Symptoms: Dyspnea, hypoxemia, subcutaneous crepitus, chest discomfort.
  • Signs: Tachypnea, decreased breath sounds, palpable subcutaneous emphysema.
• Radiology:
  • CXR:
    • Findings: Linear or bubble-like lucencies in the lung interstitium.
    • Associated Findings: Pneumothorax, pneumomediastinum, or subcutaneous emphysema.
  • CT:
    • Parts: Air tracking along bronchovascular bundles and interlobular septa.
    • Size: Variable air pockets depending on severity.
    • Shape: Irregular, linear, or cystic.
    • Position: Interstitial and peribronchial.
    • Character: Non-enhancing air-filled spaces.
    • Time: Acute onset, often related to ventilation or trauma.
    • Associated Findings: Pneumothorax, air embolism.
  • Other relevant Imaging Modalities:
    • MRI: Rarely used, but could show air voids with signal loss.
    • PET-CT: Limited utility unless associated with malignancy.
    • Ultrasound: May show “comet-tail” artifacts from air in interstitial spaces.
    • Angiography: Not typically relevant.
• Pulmonary function tests (PFTs):
  • Reduced lung compliance and gas exchange abnormalities may be noted.
• Management:
  • Address underlying cause (e.g., adjust ventilator settings in barotrauma).
  • Supportive care: Oxygen therapy, monitoring for complications.
  • In severe cases: Surgical intervention (e.g., drainage of pneumothorax).
• Recommendations:
  • Minimize ventilator pressures in at-risk patients.
  • Early identification and management of symptoms to prevent progression.
  • Monitor closely in neonates and trauma patients.
• Key Points and Pearls:
  • Interstitial emphysema is often secondary to trauma or ventilation in critically ill patients.
  • Radiology is key for diagnosis, with CT providing the best detail.
  • Prompt identification and addressing the underlying cause are crucial to prevent complications.