Barotrauma and COVID-19

Excerpt

The evidence of the extra-alveolar air (EAA) described in a recent publication in Intensive Care Medicine [1] is explained in an important publication by Macklin and Macklin in the 1940s [2]. Over many years, they applied increasing pressure to anaesthetised cats and carefully dissected them. Initially, the air bursts the alveoli and forms small bubbles which move into the adventitia of the venules and arterioles. The air forms pulmonary interstitial emphysema, which initially moves to form mediastinal emphysema. From there, with increasing pressure, the EAA initially forms subcutaneous emphysema, then pneumothoraces directly from the air under pressure in the mediastinum, not as commonly thought, from blebs on the surface of the lungs. With further pressure, the EAA moves along the large vessels into the retroperitoneum to form pneumoretroperitoneum. This explains the air in the case report [1]. When large pressures are applied to the lungs, the EAA can also form pneumoperitoneum. Bursting of the alveoli can occur because of high inspiratory pressure, hyperexpansion or direct damage to the alveoli. Understanding the origin of EAA when lungs are exposed to high pressures and/or volumes is the key to one of the most important advances in intensive care medicine, the universal application of low tidal volumes and limited inspiratory pressures. …