The role of Macklin effect in management of ARDS: beyond spontaneous pneumomediastinum

Barotrauma (including pneumomediastinum, pneumothorax or subcutaneous emphysema) is a frequent complication of patients with acute respiratory distress syndrome (ARDS) and is associated with worse outcome. Furthermore, some Authors hypothesize that pneumomediastinum could be a sign of ongoing patient self-inflicted lung injury (P-SILI) in patients with respiratory failure receiving non-invasive respiratory support. It has been recently found that a well-known radiological sign, the Macklin effect (or pulmonary interstitial emphysema), could be a powerful predictor of subsequent development of barotrauma in patients with ARDS (sensitivity = 89.2% (95% confidence interval (CI): 74.6 to 96.9); specificity = 95.6% (95% CI: 90.6 to 98.4)). Of note, Macklin effect is visible on chest computed tomography (CT) scan 8–12 days before overt barotrauma. Furthermore, patients with Macklin effect not currently receiving invasive ventilation have a high risk of subsequent intubation. Accordingly, it could be hypothesized that Macklin effect could be a marker of lung fragility, disease severity, and P-SILI in patients with ARDS. Therefore, detection of Macklin effect on chest CT scan could be used to stratify baseline risk of patients with ARDS, select which patients should be evaluated for alternative management algorithms, including advanced respiratory monitoring, ultraprotective ventilation, or institution of extracorporeal support without invasive ventilation.