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Emergency And Acute Medicine – Pneumomediastinum
Pneumomediastinum refers to the presence of free air within the mediastinum. It may arise from the esophagus, lungs, or bronchial tree and can occur spontaneously (primary pneumomediastinum) or secondary to trauma, instrumentation, surgery, infection, or barotrauma. Spontaneous pneumomediastinum results from increased intra-alveolar pressure with subsequent alveolar rupture, allowing air to dissect along bronchovascular sheaths toward the hilum and into the mediastinum. Air may then track into fascial planes of the neck, producing subcutaneous emphysema. This condition is most common in young males and often follows Valsalva maneuvers such as forceful vomiting, coughing, strenuous exercise, labor, or inhalational drug use. Secondary pneumomediastinum may result from thoracic trauma, positive-pressure ventilation, esophageal rupture, or mediastinal infection. Tension pneumomediastinum is rare but life-threatening and may occur in ventilated patients.
Chest pain is the most common presenting symptom and is typically sharp, pleuritic, retrosternal, and sometimes radiates to the back or arms. Dyspnea is common. Patients may report neck pain, throat discomfort, dysphagia, or a sensation of neck swelling due to air tracking into cervical tissues. Subcutaneous emphysema is frequently found in the supraclavicular region and anterior neck. Dysphonia or hoarseness may occur. Hamman crunch, a precordial crunching sound synchronous with the heartbeat and best heard in the left lateral decubitus position, is pathognomonic but uncommon. In suspected esophageal rupture, Meckler triad of vomiting, lower chest pain, and cervical subcutaneous emphysema should raise immediate concern.
Evaluation must focus on excluding secondary causes, particularly esophageal rupture. Chest radiography is the most valuable initial test and should include a lateral view, as mediastinal air may be missed on a standard posteroanterior film. Radiographic findings may include mediastinal air outlining cardiac borders, subcutaneous emphysema, the continuous diaphragm sign, or the spinnaker sail sign in pediatric patients. Up to one-third of cases may have a normal chest radiograph. Chest CT is the imaging modality of choice when suspicion remains high despite a negative radiograph and is more sensitive for small air collections and associated pathology. If esophageal rupture is suspected, a water-soluble contrast esophagram is indicated. Laboratory studies are generally not diagnostic but should include CBC if mediastinitis is a concern.
Management depends on the underlying cause. Spontaneous pneumomediastinum is usually benign and self-limited, resolving within several days. Treatment consists of oxygen supplementation, analgesia, rest, and reassurance. High-flow oxygen may accelerate reabsorption of mediastinal air. Oral intake should be withheld if an esophageal source is suspected until diagnostic evaluation is complete. Secondary pneumomediastinum requires directed therapy toward the underlying condition, such as management of asthma exacerbation, diabetic ketoacidosis, trauma, or esophageal injury. Broad-spectrum antibiotics are indicated if mediastinitis is suspected. Tube thoracostomy is reserved for associated significant pneumothorax, and pericardiocentesis is indicated only in tension pneumopericardium with hemodynamic compromise.
Admission is warranted for secondary pneumomediastinum, suspected esophageal rupture, associated pneumothorax, abnormal vital signs, significant comorbidities, or unreliable follow-up. Patients with uncomplicated spontaneous pneumomediastinum, stable vital signs, no pneumothorax, and symptom improvement after observation may be discharged with close outpatient follow-up. Recurrent cases may require cardiothoracic evaluation.
Clinicians must maintain a high index of suspicion in patients with chest pain, dyspnea, and neck swelling, particularly in the setting of vomiting, asthma exacerbation, or inhalational drug use. Although often benign, failure to exclude esophageal rupture or other serious secondary causes can result in significant morbidity and mortality.
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