Tension pneumothorax during extracorporeal membrane oxygenation.

Life-threatening tension pneumothorax in neonates on extracorporeal membrane oxygenation (ECMO) has been associated with an increase in arterial oxygen tension and a decrease in peripheral perfusion, followed by a decrease in ECMO flow with progressive hemodynamic deterioration. To investigate this triad, chest tubes were placed bilaterally in 9 dogs to allow injection of air to produce tension pneumothorax. Six dogs were subsequently placed on standard venoarterial ECMO before the reinduction of tension pneumothorax. Measured values included arterial pulse pressure, inferior vena cava pressure, systemic arterial blood gases, peripheral arterial oxygen saturation, mixed venous oxygen saturation, and left heart cardiac output. Oxygen delivery was calculated from directly measured values. Each of the 6 dogs on ECMO demonstrated the triad of increased arterial oxygen tension (92 +/- 7 to 325 +/- 20 mm Hg; p less than 0.05), decreased peripheral perfusion (as evidenced by a decrease in pulse pressure from 55 +/- 4 to 31 +/- 5 mm Hg; p less than 0.05), and decreased mixed venous oxygen saturation (71% +/- 3% to 22% +/- 2% saturation; p less than 0.05) followed by a lower ECMO flow with progressive hemodynamic deterioration (oxygen delivery decreased from 285 +/- 11 to 111 +/- 12 mL/min; p less than 0.05). Aspiration of the intrathoracic air allowed return to baseline ECMO flow and hemodynamic stability in all dogs. The triad of increased arterial oxygen tension and decreased peripheral perfusion (as evidenced by a lower arterial pulse pressure and lower mixed venous oxygen saturation) followed by decreased ECMO flow with progressive hemodynamic deterioration consistently appears when tension pneumothorax occurs on ECMO.