Coronavirus Associated Pneumomediastinum and Pneumothorax - COVIMIX Study

Spontaneous pneumomediastinum (PMS) is defined as free air within the mediastinum. Spontaneous pneumothorax (PNX) consists of the presence of air inside the pleural space. PMS and PNX may sometimes occur secondly to an underlying pathology, or deriving from a sudden increase in intra-alveolar pressure such as functional alteration such as airway hyperactivity, Valsalva maneuver, cough, barotrauma, and/or volutrauma with consequent rupture of the alveoli and subsequent leakage of air into the mediastinum due to the Macklin effect. The escaping air can then spread inside the pericardium, the peritoneum, the muscles, and subcutaneous tissues, hence causing subcutaneous emphysema.

PMS and PNX are rare complications of several lung infections such as Pneumocystis Jirovecii pneumonia, tuberculosis, bacterial necrotizing pneumonia, and herpes pneumonia.

However, an increasing number of PMS and PNX has been described in patients with SARS-CoV2 interstitial pneumonia. PMS and PNX can either present as the onset manifestation of COVID-19 disease, or occur as complications of non-invasive and/or invasive ventilation, or following to cystic and/or fibrotic evolution of the pathology.

The frequency of PMS and PNX during COVID-19 is not well defined, as the available data are limited to case collections and single reports. According to currently available scientific literature, PNX in COVID-19 occurs with frequency rates of 1-3%, up to 6% in patients undergoing non-invasive ventilation (NIV) and mechanical artificial ventilation (VAM). In McGuinness's analysis, which compared the complications of barotrauma in patients with acute respiratory distress syndrome (ARDS) in VAM, PNX and PMS occurred with frequency rates of 9% and 10%, respectively, while in non-COVID-19 population, PNX and PMS frequency rates were 12% and 3%, respectively.