Abstract
The presence of air in the mediastinum is a rare finding called pneumomediastinum. Spontaneous pneumomediastinum is typically benign. Marijuana use has been rarely reported to cause pneumomediastinum. Our case series presents two young men with no significant past medical history who had a history of marijuana use and developed pneumomediastinum after multiple episodes of intractable vomiting. The pathophysiology of spontaneous pneumomediastinum in marijuana users includes cyclic vomiting or microperforation of the esophagus or barotrauma during breathing maneuvers. Most cases can be managed conservatively.
Keywords: Marijuana use, Muller’s maneuver, pneumomediastinum, Valsalva maneuver
Pneumomediastinum is a rare condition in which air is present in the mediastinum, possibly resulting from physical trauma, respiratory diseases, iatrogenic causes, or other situations that contribute to air escaping from airways, lungs, or the gastrointestinal tract into the mediastinum. A recent retrospective study revealed that 14 of 21 cases of spontaneous pneumomediastinum had a history of inhaled marijuana use.1 The major presentation is acute retrosternal chest pain, and 70% of the patients develop subcutaneous emphysema. Anterior chest x-rays can diagnose most cases. For inconclusive cases, chest computed tomography (CT) is utilized to confirm the diagnosis. We report two 20-year-old white men who developed spontaneous pneumomediastinum after marijuana use.
CASE SUMMARY
A 20-year-old man who used marijuana occasionally was admitted due to intractable nausea and vomiting (Table 1). An initial chest x-ray revealed subcutaneous emphysema in the left supraclavicular region, and CT of his abdomen and pelvis showed free air in the posterior mediastinum (Figure 1a). Another 20-year-old white man with marijuana use presented with dyspnea and intractable vomiting (Table 1). The initial chest x-ray showed pneumomediastinum, and CT of the chest also revealed pneumomediastinum (Figure 1b). In both cases, an esophagogram did not reveal any extravasation of contrast.
Table 1.
Pertinent observations in the two 20-year-old white men
| Variables | Case 1 | Case 2 |
|---|---|---|
| Duration of marijuana use (years) | Unknown | 4 |
| Onset of symptoms (days) | 3 | 1 |
| Past medical history | None | None |
| Presenting symptoms | ||
| Nausea/vomiting | + | + |
| Hematemesis | 0 | + |
| Chest pain | + | 0 |
| Epigastric pain | + | 0 |
| Dyspnea | 0 | + |
| Physical examination | ||
| Subcutaneous emphysema | 0 | + |
| Rebound tenderness | 0 | 0 |
| Vital signs | ||
| Body temperature (°F) | 98.9 | 99.8 |
| Heart rate (beats/min) | 91 | 112 |
| Respiratory rate (/min) | 16 | 23 |
| Blood pressure (mm Hg) | 135/90 | 110/70 |
| Oxygen saturation (%) | 98 | 96 |
| Initial laboratory results | ||
| White blood cell count (/µL) | 17,170 | 21,880 |
| Hemoglobin (g/dL) | 12.8 | 16.2 |
| Platelets (/µL) | 197,000 | 365,000 |
| Lipase (IU/L) | 9 | 16 |
Figure 1.
Chest x-rays showing subcutaneous emphysema and CT scans revealing pneumomediastinum in (a) Case 1 and (b) Case 2.
DISCUSSION
Marijuana, rarely reported as a cause of pneumomediastinum, is the most commonly used psychotropic drug in the United States, after alcohol. In 2018, more than 11.8 million young adults reported marijuana use in the past year.2 For marijuana users, the precipitating factors for spontaneous pneumomediastinum are different from those of most patients and include smoking techniques and marijuana-induced vomiting. Coughing, generally the most common precipitating factor, remains a factor, but is less common than vomiting in this group of patients. Weiss et al1 evaluated the frequency of marijuana use in patients with nontraumatic pneumomediastinum. Concurrent risk factors including vomiting (57.1%) and coughing (42.9%) were commonly present.
The limitation in our study was that the length of use, amount of marijuana, and smoking techniques were not documented precisely; this information has epidemiologic interest as future studies may want to determine if a cumulative effect of marijuana smoking is present. The strength of our study is that the diagnosis of spontaneous pneumomediastinum was confirmed with CT scan, esophagogram, and esophagogastroduodenoscopy. Therefore, secondary pneumomediastinum was excluded.
Spontaneous pneumomediastinum in marijuana and substances users is believed to result from either tearing the esophagus due to cyclic vomiting or microperforation of the esophagus3 or from barotrauma during breathing maneuvers.1,2 Common breathing maneuvers in marijuana users, i.e., the Valsalva maneuver (forced expiration through resistance) and Muller’s maneuver (deep inspiration through a device with airflow resistance), are believed to cause spontaneous pneumomediastinum.4 Positive pressure devices have been related to barotrauma and pneumomediastinum; however, spontaneous mediastinum can also develop without using a smoking device.5
An anterior view chest x-ray provides the diagnosis in 90% of reported cases. CT scan of the chest is useful to confirm the diagnosis in inconclusive cases, assess the extent of pneumomediastinum, and identify the causative pathologies.3 Most cases resolve by themselves and therefore can be managed conservatively, unless they progress to malignant pneumomediastinum. In that case, thoracotomy or video-assisted thoracoscopy may be necessary for decompression.
References
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