One of the most life-threatening causes of pneumomediastinum is Boerhaave syndrome in which there is a spontaneous rupture of the esophagus.3 In addition, as previously mentioned, numerous illicit drugs (eg, cocaine, marijuana, ecstasy) have been implicated in pneumomediastinum—with cocaine posing the greatest risk.8,9 Perna et al8 relate cocaine-related pneumomediastinum to the direct toxic effects of the drug on the lung parenchyma in the acute phases of use and not due to pressure variations resulting from the Valsalva maneuver necessary to inhale the drug.
Predisposing risk factors for mediastinal emphysema include preexisting pulmonary disease (eg, chronic obstructive pulmonary disease, asthma) and a history of smoking.5,6,8,9 Precipitating risks include recent exercise, significant upper respiratory infection, forceful straining (eg, cough, emesis, childbirth), and diabetic ketoacidosis.6,8,9 Unlikely sources that have also been implicated are those related to surgical procedures, such as arthroscopy, adenotonsillectomy, instrumentation, and recreational activities (eg, scuba diving, playing wind instruments).3,6
Diagnosis
The diagnosis is often made clinically and confirmed radiographically.2,7 Physical examination findings vary by the extent of the mediastinal emphysema. Common findings include the Hamman sign, which has been described as classic “crunching, crackling, bubbling, and rasping sounds synchronous with peak heart beat” on auscultation.2,5,8 Air from the mediastinum may dissect into the skin, particularly in the superior structures of the neck and face, resulting in a subcutaneous emphysema described as a palpable crunching sound.2
Imaging
Obtaining a plain CXR is an acceptable standard of practice. Pneumomediastinum has been described as either a “classic hyperlucency” or, as Chiu et al5 have described, as “lucent streaks or bubbles of gas that outline mediastinal structures” on a posteroanterior and lateral film, implying damage to luminal structures of the intrathoracic cavity.2,4,5,7,9 This lucency has been further described as an outline of the inner pleura of mediastinal structures, which is a defined crease lateral to the pulmonary artery and arch of the aorta along the cardiac border (best visualized on a lateral view image).5,7 A scant amount of air, however, may not be visualized on a plain film.2,4,5,9 Therefore, the literature supports a thoracic CT as the gold standard for its greater sensitivity in visualizing a small pneumomediastinum.2,9
Treatment
Since pneumomediastinum is typically a self-limited disease, treatment is often conservative management with specific consideration to the patient’s age, severity of symptoms, underlying cause, and comorbidities.2,10 Treatment should include rest, supplemental O2, and analgesia.5,7,9 Hospitalization for an observation period of 2 to 5 days is recommended, with one study reporting an average length of stay as 3 days or until resolution of symptoms.8,9
Disposition is best determined by the patient’s clinical course; however, the risk of progression warrants observation for serial follow-up examinations and possibly repeat imaging as well as access to acute intervention, if required. Though rare, several serious comorbid conditions have been reported, including hypertensive episodes, bilateral pneumothoraxes, and even cardiac compression (or tension pneumomediastinum) limiting cardiac output and leading to cardiac arrest.2,4 Following discharge, there has been no clinical study reporting recurrence of pneumomediastinum; therefore, close clinical follow-up is not necessarily indicated.4,9
Conclusion
Pneumomediastinum is a rare complication of acute and chronic pulmonary and extrapulmonary diseases. As seen in this case presentation, the condition is typically associated with asthma exacerbations. Patients often present with chest pain, dyspnea, dysphonia, and dysphagia. Although diagnosis may be confirmed using plain CRX, CTA is the preferred modality due to its higher sensitivity in visualizing mild pneumomediastinum. While the risk of mortality is present, the condition generally follows a stable clinical course with minimal risk of long-term morbidity.
Major Howell is a physician assistant, department of emergency medicine, Wright-Patterson Medical Center, Wright-Patterson Air Force Base, Ohio. Captain Pennington is an emergency medicine physician, department of emergency medicine, Wright-Patterson Medical Center, Wright-Patterson Air Force Base, Ohio.
Acknowledgement:The authors wish to extend special thanks to Dr Nurani Kester, department of emergency medicine, San Antonio Military Medical Center, Fort Sam Houston, Texas; and to Dr Luke Simonet, department of radiology, David Grant United States Air Force Medical Center, Travis Air Force Base, California.
Disclosure: The authors report no conflicts of interest.