A 55-year-old patient experiencing severe coronavirus disease 19 (COVID-19) related acute refractory respiratory failure requiring venovenous extracorporeal membrane oxygenation (VV-ECMO) support, with femoro-femoral approach, suddenly developed both signs of drainage failure and return obstruction, with extracorporeal blood flow (EBF) inconsistency, evolving to impairment, at the same time with severe desaturation, and hemodynamic instability. To support differential diagnosis, a focused point of care lung ultrasound was performed, showing no lung sliding in all explorable left fields. Chest X-ray, immediately obtained, revealed a large left-sided tension pneumothorax (Figure 1, Figure, Supplemental Digital Content 1, https://links.lww.com/ASAIO/A814), with left lung completely collapsed, tracheal deviation, and mediastinal shift toward the right side, involving heart, superior and inferior vena cava, as suggested by displacement of intravascular devices. Particularly, drainage cannula and return cannula, are clearly visible: the latter appeared markedly misaligned with the spine, compared to previous assessments (Figure 2). After left-sided chest tube insertion, the left lung appeared mostly re-expanded (Figure 3), with mediastinal structures back to conventional anatomical site. Target EBF flow was restored, with stabilization of both hemodynamics and peripheral saturation. Small residual apical pneumothoraxes remain, with right-sided previously known, and daily assessed with lung ultrasound after chest tube insertion to manage the first episode of spontaneous pneumothorax occurred before ECMO implementation. In patients requiring extracorporeal support due to acute respiratory distress syndrome, particularly in the COVID-19 population, known to be at high risk of barotrauma,^1,2 an acute decrease in the ECMO inlet pressure (increased negativity),^3,4 deteriorating EBF, compromizing therapy effectiveness, and increased post-membrane lung (return) pressure may suggest acute development of clinically significant pneumothorax, or significant worsening of preexisting pneumothorax, requiring prompt intervention to restore cardiovascular physiology and decrease intrathoracic pressure, allowing for EBF to be early reestablished.⁵