A 29-year-old male (weight: 58 kg, length: 178 cm, BMI: 18.3 kg/m2; BMI normal range: 18.5 kg/m2 - 25 kg/m2), without significant past medical history, presented at the ED with chest pain and localised neck tenderness. He presented with sudden onset retrosternal chest pain. The pain was described as "mild and continuous" with no radiation or any other associated symptoms (i.e., no dyspnea or cough; no nausea or vomiting). There was no history of preceding trauma, and the patient had no previous medical history of note. Apart from a 5 pack-year history of smoking cigarettes, there were no other cardiovascular risk factors.
The patient did not take regular medication but admitted to marijuana use on a weekly basis as a teenager until the age of 25. He then only used marijuana infrequently (on average once a month). With regard to cocaine, he admitted he had used it twice:the first being a year ago, and the second time a day prior to attending the ED. There was no history of any other recreational drug use.
Following intranasal cocaine inhalation at an evening social gathering, he suffered chest pain and palpitations. In an attempt to ease the chest pain, he smoked a premixed marijuana/tobacco joint (approximately 0.32 grams marijuana). The joint was smoked as per a normal cigarette technique without prolonged inhalation or Valsalva manoeuvres.
The following morning, he continued to experience retrosternal chest pain, which had since increased in intensity. He now noticed the presence of right-sided neck pain but without muscle tenderness, throat pain, or dyspnea. Despite taking 1 gram of paracetamol, the symptoms were no better and he therefore presented to the ED.
His vital signs were within normal parameters (temperature: 36.1 C, heart rate: 65 bpm, blood pressure: 125/75 mmHg, equal bilaterally with no pulsus paradoxus, respiratory rate: 13/min, oxygen saturation 100% on room air with a GCS of 15/15).
On physical examination, respiratory auscultation was normal without additional sounds; cardiac sounds were unremarkable with no murmurs or clear "Hamman's sign" (a crunching sound synchronous with the heartbeat. It is best heard over the precordium and is suggestive for pneumopericardium or -mediastinum). A moderate amount of subcutaneous emphysema on the right side of the neck was noted. The rest of the physical exam was unremarkable.
Blood analysis was normal (normal haematology and biochemical analysis, normal inflammatory markers and troponins <0.012 ng/mL). Arterial blood gas on room air demonstrated a respiratory alkalosis without metabolic compensation (pH 7.50, pCO2 29.3 mmHg, pO2 119.7 mmHg, base excess 0.3 mmol/L, HCO3- 22.2 mmol/L, saturation 98.2%, and lactate 1.3 mmol/L). ECG demonstrated normal sinus rhythm without ST-elevation with normal repolarisation. A chest X-ray showed subtle evidence of pneumomediastinum and right-sided mild subcutaneous emphysema in the neck (Figure 1(a), thick arrow) with air tracking in the centre of the mediastinum (Figure 1(a), thin arrow). There is a small denser line along the right cardiomediastinal margin (Figure 2) that is often present in normal X-rays and is attributed to an optical illusion known as the Mach Band effect (a visual pattern due to edge enhancement manifesting as a region of lucency adjacent to convex surfaces). Although it can be normal, taken in association with subcutaneous emphysema and air tracking in the centre of a mediastinum, this is suggestive of a pneumomediastinum.
As subcutaneous emphysema along with the suggestion of pneumomediastinum was identified on the chest X-ray, further workup with thoracic CT-scan was performed. This confirmed the presence of subcutaneous emphysema with a pneumopericardium, a large pneumomediastinum, and a small pneumothorax (Figure 1(b), Figure 3). The patient was managed conservatively and kept overnight for observation (continuous cardiac and pulse oximetry monitoring with two-hourly blood pressure measurement in addition to pain control titrated to a pain Visual Analogue Scale). A combination of paracetamol and tramadol was sufficient to keep the patient pain free. The following day, his clinical parameters remained within normal limits along with the resolution of chest pain and a largely unremarkable physical examination. He was discharged the next day with expectative approach, oral analgesics, and ambulatory follow-up. Repeat CT after two weeks revealed complete resolution of the free intrathoracic air.