Discussion
Tension pneumomediastinum (TPM) is caused by direct injury or barotrauma to the tracheobronchial tree, alveoli, or esophagus, leading to air leakage into the mediastinum and causing tension in the closed cavity. This may cause compression of large vessels, heart, and lungs leading to cardiovascular and respiratory compromise, which can be a threat to the patient’s life.2, 4 COVID-19 infection attacks initially the respiratory system causing pneumonia. Complications include acute respiratory distress syndrome requiring invasive ventilation with higher or maximum ventilator settings. This carries an increased risk of barotrauma to the lungs and tracheobronchial tree. There is not much literature about COVID-19 pneumonia and complicating into TPM or pneumomediastinum, there are only one case report of TPM, and a series of 8 cases of pneumomediastinum are described till date.2, 3, 5-7 COVID-19 infection is known to cause airway inflammation and edema, which puts these patients at a higher risk of airway tract injuries following instrumentation.3Placement of a large size endotracheal tube (ETT) also carries a risk of development of TPM in COVID-19 patients.3 Although in our case series, only one patient had a tracheal injury but three patients required reintubation due to secondary bacterial and fungal pneumonia with increased risk for TPM.
All our patients were given intermittent prone positioning after the intubation as a therapeutic approach for COVID19 respiratory failure. Prone positioning in acute respiratory distress patients is known to be a risk factor for the development of pneumomediastinum and TPM.8 Wali et al. described in their case series that one of their COVID-19 patients developed pneumomediastinum immediately after prone positioning.3 All our patients had pneumo-mediastinum at day 10 post-intubation or later. They had secondary bacterial and or fungal pulmonary infections. The majority of our patients also had complex previous medical histories, which may be contributing to their frail condition.
For the diagnosis of TPM apart from hemodynamic instability, imaging studies are confirmatory. Initial CXR will show the presence of air in mediastinum, around or earth heart sign due to collapsed and restricted filling of the heart chambers. 9 Sometimes, it’s difficult to see the heart shadow in the x-ray of TPM patients; hence it is called ”vanished heart sign”. 10 A computerized tomography of the chest will show more detailed extension of air in the mediastinum, including the retromediastinum.3
TPM is treated with insertion of suprasternal drains or through xiphisternum to decompress the mediastinum. The conservative management includes reducing airway pressures, allowing permissive hypercapnia and denitrogenation of the mediastinum air by increasing the percentage of oxygen supplementation.2, 3 Two of our patients were managed by insertion of the intercostal drain and three patients were managed conservatively. One patient required extracorporeal membrane oxygenation (ECMO) therapy. One of conservatively managed and one patient managed with drainage of TPM died later due to other complications.