What is pneumomediastinum?

Pneumomediastinum: Definition, Diagnosis, and Management

Pneumomediastinum is defined as the presence of free air in the mediastinal cavity, which can result from various causes including trauma, medical procedures, or occur spontaneously without a clear etiology. 1, 2

Etiology and Classification

Pneumomediastinum is classified into two main categories:

1. Secondary pneumomediastinum: Occurs with an identifiable instigating event such as:

   • Trauma (blunt thoracic trauma) 3
   • Iatrogenic causes (endoscopic procedures, esophageal dilation) 4
   • Barotrauma (diving, mechanical ventilation) 1
   • Operative procedures (including laparoscopic surgeries) 5

2. Spontaneous pneumomediastinum (SPM): Occurs without a clear etiology, often in young adults 6, 7

Clinical Presentation

Common symptoms and signs include:

• Central chest pain/discomfort (most common symptom) 1, 2
• Dyspnea or labored breathing
• Voice distortion
• Subcutaneous emphysema affecting face, neck, and chest
• Hamman's crunch (a "crunching" sound synchronized with the cardiac cycle, present in approximately 20% of cases) 6, 2
• Symptoms mimicking cardiac tamponade due to increased intrapulmonary pressure 2

Diagnostic Evaluation

1. Imaging studies:

   • Contrast-enhanced CT scan is the imaging examination of choice (sensitivity 92-100%) 4
   • Chest X-ray may show radiolucent airline in the mediastinum and/or surrounding the heart 2, 5
   • CT can also help assess extension to adjacent structures and rule out other conditions 4

2. Signs on imaging:

   • Air collection in the mediastinum
   • Pleural effusion
   • Subcutaneous emphysema
   • Pneumothorax
   • Lung collapse 4

Management Approach

Most cases of pneumomediastinum follow a benign course and can be managed conservatively:

1. Conservative management for uncomplicated cases:

   • Observation
   • Pain control
   • Oxygen therapy (high-flow humidified oxygen for patients with airway compromise) 4
   • Rest
   • Avoidance of maneuvers that increase intrathoracic pressure 1, 2

2. Monitoring:

   • Close observation for signs of deterioration
   • Monitoring of vital signs, respiratory rate, oxygen saturation
   • Consider capnography for early detection of airway obstruction 4

3. Surgical consultation is recommended for cases with:

   • Suspected esophageal perforation
   • Airway injury
   • Hemodynamic instability
   • Worsening symptoms 1

Special Considerations

1. Esophageal perforation:

   • Mortality ranges between 10-20%
   • Delay in treatment is the most important predictor of survival 4
   • Suspect if patient develops pain, breathlessness, fever, or tachycardia after procedures 1

2. Post-procedural pneumomediastinum:

   • Following endoscopic procedures, complication rate is approximately 2.6% 1
   • Requires close monitoring for signs of perforation

3. Traumatic pneumomediastinum:

   • Often incidental finding in blunt thoracic trauma
   • Conservative management is usually sufficient in the absence of aerodigestive tract injury 3

Prognosis

The disease typically follows a benign evolution with the air in the mediastinum being gradually resorbed by surrounding tissues. Relapses are rare, and most patients recover completely with conservative management 2, 7.

Warning Signs Requiring Urgent Attention

• Severe pain (deep cervical pain, chest pain, dysphagia, painful swallowing)
• Fever and crepitus (may indicate mediastinitis)
• Agitation or complaints of difficulty breathing
• Progressive subcutaneous emphysema
• Hemodynamic instability 4

Pneumomediastinum should be part of the differential diagnosis for any patient presenting with chest pain of unknown etiology to ensure prompt diagnosis and appropriate management 6.