An 18 year male presented to the ED with complaints of 48 hours of chest pain radiating towards the neck associated with a sensation of fullness of the upper chest. He began a vigorous bench pressing regimen about two weeks prior to admission (PTA) with last session 5 days PTA. History is remarkable for exercise-induced asthma and for regular marijuana use. He sustained a close range gunshot wound to the epigastrium 18 months prior to presentation. Injuries to the liver and pancreas required laparotomy and repair, but there was no apparent injury to the thorax or diaphragm; no chest tube was required. Exam revealed subcutaneous emphysema and minimal chest wall tenderness on palpation. Chest X-ray showed extensive mediastinal and subcutaneous emphysema. Chest CT confirmed the same. In part owing to concerns surrounding prior trauma, the patient was admitted to the ICU overnight for close observation. He remained clinically stable throughout the hospital course and was discharged on hospital day three.
Discussion:
The pathophysiology of SPM is described as the development of a decreasing pressure gradient between alveoli and lung interstitium as during Valsalva maneuver or Muller maneuver in asthma. Rupture of alveolo-capillary membrane occurs and air circulates centripetally through the venous sheaths to the hilum and mediastinum (Macklin effect). Spontaneous pneumomediastinum and pneumothorax has reportedly been associated with breath holding competition in marijuana smokers, inhalational drug use, asthmatic and mostly in young males. We believe that Valsalva associated with bench-pressing may have initiated the sequence in this case. Several algorithms have been proposed for diagnosis and management. Decision to do further imaging CT or esophagram should be individualized clinically; the latter is indicated if esophageal rupture is suspected. Extensive workup is usually not necessary. Serial radiographs do not typically change management. Disposition of SPM at presentation can be confusing. If the patient is hemodynamically stable and serious secondary associations are less likely or ruled out, ICU admission is not mandatory. Patients can be observed on medical floor or even as outpatient with close follow up. Our patient recovered without incidence.
Conclusions:
Spontaneous pneumomediastinum (SPM) is defined as the presence of free air or other gas in the mediastinum in the absence of apparent precipitating factor. It is an uncommon benign cause of chest pain or dyspnea. It is commonly described in adolescents and young adults. Despite its benign course, initial presentation to primary care or ED can be challenging.