Our case series focusses on the development of spontaneous pneumomediastinum, pneumothorax or surgical emphysema in the three COVID-19 diagnosed cases with no previous history of intubation and one patient with a history of intubation developing subcutaneous emphysema post-intubation. Pneumomediastinum is most often caused by increased airway pressures, secondary to mechanical ventilation or airway obstruction; however, other causes include a rise in intrathoracic pressure (such as from the Valsalva manoeuvre); strenuous activity; severe vomiting (diabetic ketoacidosis, anorexia nervosa); trauma to the thoracic cavity; oesophageal rupture; thoracic and head and neck surgery, particularly with resultant tracheobronchial injury; and alveolar injury due to underlying diseases such as infection and sarcoidosis .
Contrary to the previous statement, we see that the findings revealed on chest CT was noted even before any iatrogenic intervention was performed which led us to believe that these severe conditions were sequelae of COVID-19 rather than being an adverse effect of mechanical/barotrauma. One of the most important points to be noted here is that none of the four patients had any previous history of respiratory disorder or smoking habit. There have been previous case reports citing similar data in the setting of COVID-19 [4, 5]. One of the possible mechanisms of injury involved in these cases could be a result of diffuse alveolar injury in severe COVID-19 disease, wherein the alveoli may be prone to rupture . Two of our patients had a cough which could also be an additive factor in alveolar rupture. This may lead to spontaneous pneumomediastinum through Macklin’s phenomenon. Interstitial air can then dissect into the mediastinum, pleural cavity and subcutaneous tissues. Similar pathological progressions have been previously observed in a variety of viral pneumonia . Macklin described how alveolar air which is released from alveolar rupture tracks along peribronchial vascular sheaths towards the mediastinum .
While searching for literature, a prior study showed that only about 1% of COVID-19 patient has pneumothorax . In our centre, a study on 3500 patients revealed only 15 (0.43%) patients developing pneumothorax, pneumomediastinum or subcutaneous emphysema with intubation-related barotrauma being attributed as the aetiology to 12 cases (80%) while 20% cases were designated spontaneous, as a sequela of COVID-19. Rupture of emphysematous bulla could be one of the causes of the development of pneumothorax which subsequently could result in subcutaneous emphysema. The literature search revealed a case study in which the patient similarly had spontaneous pneumothorax, pneumomediastinum and surgical emphysema similar to case 2 in our series .
Dyspnea being a non-specific symptom could be present in moderate to severe COVID-19, pneumomediastinum and pneumothorax. All the four patients had dyspnea and three of four patients developing a cough and two of the three patients presenting with fever. All four patients needed mechanical ventilation to overcome the dyspnea. Two of the four patients had a fatal outcome. It is worthwhile to note that three of four patients belonged to a young age group.
The fourth patient in our series presented with all the usual symptoms of COVID-19 and showed GGO and consolidation in the initial CT scan without any signs of pneumomediastinum. It is only after the intubation that the patient developed pneumomediastinum and subcutaneous emphysema. COVID-19 is recognised as an aetiological factor for causing central and upper airway inflammation and oedema leaving patients potentially vulnerable to injury from instrumentation. Furthermore, expeditious intubation due to severe hypoxaemia in emergent settings could be a contributory factor to the tracheobronchial injury . Subcutaneous emphysema is the most common finding in tracheal lacerations. It serves as the sentinel sign that stimulates further confirmatory studies to establish the diagnosis. Other signs include mediastinal emphysema, pneumothorax, dyspnea, dysphonia, cough, hemoptysis and pneumoperitoneum . The process to reposition the patient to prone in heed to balance the ventilation-perfusion mismatch has certain risks of its own  and could have been one of the factors following which there is an increased chance of the injury of an already susceptible tracheobronchial tree.
Chest x-ray is the diagnostic standard for pneumomediastinum, half of all cases may be missed without a lateral film . CT scan remains the definitive diagnostic tool. This will demonstrate subcutaneous emphysema, pneumopericardium and potential tracheobronchial injuries alongside the bilateral infiltrates typical of COVID-19 .