An Uncommon Cause of Spontaneous Pneumomediastinum and Subcutaneous Emphysema

Edwards, Michael; Ramappa, Arun Jeenahalli

A 79-year-old gentleman presented with a 4-day history of increased shortness of breath, pleuritic chest pain, fevers, and non-productive cough. His past medical history included Parkinson's disease, ischaemic heart disease, and hiatus hernia. He had previously been endoscopically investigated for dysphagia with no firm diagnosis. On admission the patient had a Modified Early Warning Score (MEWS) of 5. He was tachycardic (130 beats per minute), tachypnoeic (36 breaths per minute), hypotensive (105/68 mmHg), and febrile (39.0°C), with oxygen saturations of 92% on room air. An initial Arterial Blood Gas (ABG) showed pH 7.503, pCO 2 3.60, pO 2 7.66, SO 2 92.5%, and lactate 3.0. On examination there was reduced air entry in the right upper zone and right basal crepitations. Initial bloods showed a White Blood Cell (WBC) count of 1.6, C-reactive Protein (CRP) of 320, and an Acute Kidney Injury (AKI) stage 1 (Creatinine 108, Urea 13.3). Electrocardiography showed sinus tachycardia and chest x-ray confirmed extensive right lower zone consolidation. A diagnosis of aspiration pneumonia with AKI secondary to sepsis was made. The patient's initial treatment included intravenous amoxicillin and metronidazole alongside intravenous fluids. On day 3 of admission the patient was afebrile with a blood pressure of 118/76 mmHg, oxygen saturations of 92% on 2 litres of oxygen per minute, and had a respiratory rate of 20 breaths per minute. Bloods showed CRP 297, WBC 8.0, and improved renal function. After 4 days of intravenous antibiotics, the patient became tachycardic and tachypnoeic with increasing oxygen requirements at rest. Coarse crackles still existed in the lung's right lower zone. After discussion with microbiology, the patient was switched to intravenous piperacillin with tazobactam and clarithromycin. The patient subsequently developed considerable subcutaneous emphysema in the right hemithorax, right neck, and right upper limb. His oxygen saturation was 90% on 35% oxygen, which was then titrated upwards to ensure saturations >94%. ABG on 35% oxygen showed Type 1 Respiratory Failure (pCO 2 4.09, pO 2 6.88, sO 2 89.9%). Blood pressure remained stable with a soft, non-tender abdomen and no external signs of chest wall trauma. A repeat chest x-ray showed extensive subcutaneous emphysema and led to a diagnosis of suspected pneumomediastinum. After discussion with the respiratory team, an urgent CT scan was requested. The scan identified marked bilateral consolidation (worse on right side), significant subcutaneous emphysema of the chest extending up to the neck (worse on the right), extensive pneumomediastinum, and a right 2-3 mm anterior pneumothorax. There was no pre-existing lung disease. It was concluded that the pneumomediastinum and subcutaneous emphysema were secondary to severe pneumonia. The patient's subcutaneous emphysema descended into his abdominal wall and lower limbs. The case was discussed with cardiothoracic surgery and interventional radiology but it was concluded that interventions were not possible. An intensive care review decided that both invasive and non-invasive ventilation would worsen the clinical situation. The patient was treated with high-flow oxygen using a nonbreathe mask. Following microbiology advice, clindamycin was prescribed in addition to piperacillin with tazobactam and clarithromycin. The patient clinically deteriorated while receiving maximum ward-based treatment. In view of the patient's guarded prognosis a