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Pneumomediastinum

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Pneumomediastinum, Hamman's Crunch, Hamman Sign

  • Pathophysiology
  1. Sources
    1. Spontaneous rupture of alveolus or bleb
    2. Tracheobronchial Injury (Trauma)
    3. Boerhaave's Syndrome (Esophageal Rupture)
  2. Results from increased pressure gradient
    1. Negative (Inhalation)
    2. Positive (Valsalva)
  3. Air tracks along vessels and Bronchi
  4. Air coalesces in mediastinum
  • Causes
  1. Secondary Pneumomediastinum (may be life-threatening)
    1. Tracheobronchial Injury (Trauma, Foreign Body Aspiration)
    2. Boerhaave's Syndrome (Esophageal Rupture, sharp Foreign Body Ingestion)
  2. Spontaneous Pneumomediastinum (tends to be benign)
    1. Inhalation Drug Use (e.g. Huffing)
      1. Inhalation Drug Users may perform action similar to Muller Maneuver
      2. Forced inspiration against a closed mouth and nose (opposite Valsalva Maneuver)
    2. Asthma
    3. Coughing
    4. Vomiting
    5. Weight lifting
    6. Vaginal Delivery
    7. Mechanical Ventilation
  • Symptoms
  1. Sore Throat
  2. Dyspnea
  3. Pleuritic Chest Pain
    1. Worse with lying
    2. Better with sitting
  • Signs
  1. Subcutaneous Emphysema
  2. Hamman's Crunch (50%)
    1. Sound heard synchronous with heart beat
  • Differential Diagnosis
  • Imaging
  1. Chest XRay
    1. As many as 50% Pneumomediastinum cases are missed on PA Chest XRay
      1. Observe for a stripe of air extending superiorly from hilum, parallel to mediastinum
    2. Review Lateral Chest XRay carefully
    3. Consider lateral neck XRay
      1. Air tracks between posterior pharyngeal wall and Vertebrae
      2. Air is more easily seen on this view, than Chest XRay
    4. Named Signs
      1. Naclerio V Sign
        1. Sharp, well demarcated "V" along the left heart border and left diaphragm
      2. Continuous Diaphragm Sign
        1. Air below the heart results in a continuous line across the diaphragm
  2. Chest CT
    1. Small Pneumomediastinum is not uncommon on Trauma chest CT
  • Management
  1. Primary Pneumomediastinum (e.g. due to excessive coughing, Asthma)
    1. Often a benign, incidental finding on CT Imaging
  2. Secondary Pneumomediastinum (e.g. Tracheobronchial Injury, Esophageal Rupture)
    1. Serious, potentially life threatening finding
    2. Intensive Care Unit Admission and thoracic surgery Consultation
  • Complications
  1. Tension Pneumomediastinum (rare)
    1. Presents with Hypotension
    2. Acute stabilization requires suprasternal notch Blunt Dissection (relieves tension)
  • References
  1. Swadron (2019) Pulmonology 2, CCME Board Review, accessed 6/18/2019