Pneumothorax and other manifestations of pulmonary air leak (pneumomediastinum, subcutaneous emphysema) are well-known complications of coronavirus disease 2019 (COVID-19). The overall incidence of these complications in COVID-19 patients has been estimated to be 1% [1]. However, in mechanically ventilated COVID-19 patients, the incidence of pneumothorax and air leaks rises to 15% [2]. Despite the widespread use of protective ventilation techniques these complications remain a major concern. Severe cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia present with acute alterations such as pulmonary edema and diffuse alveolar damage [3], with a classical acute respiratory distress syndrome pattern. As a result of acute-phase alterations, there may be a negative evolution towards parenchymal consolidations and fibrosis. Due to these processes, COVID-19 patients could present with inhomogeneous pulmonary parenchyma and reduced compliance. Inhomogeneous parenchyma facilitates acute air leaks through the maldistribution of ventilatory stress (Figure 1) because two contiguous lung zones with different elasticity develop different local stresses [4]. Reduced compliance promotes lung injury and also tends to hinder re-expansion of the lungs after air drainage (Figure 2). These factors are also involved in self-inflicted lung injury [5] and could explain the growing number of cases of pneumothorax and acute air leaks in COVID-19 patients undergoing noninvasive protective ventilation (Figure 3).
REFERENCES
1. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet. 2020; 395:507–13.
2. Benson JC, Carlson ML, Lane JI. MRI of the internal auditory canal, labyrinth, and middle ear: how we do it. Radiology. 2020; 297:252–65.
3. Bradley BT, Maioli H, Johnston R, Chaudhry I, Fink SL, Xu H, et al. Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series. Lancet. 2020; 396:320–32.