What is the primary mode of gas exchange in ECMO?

The primary mode of gas exchange in ECMO is through extracorporeal blood oxygenation. In ECMO, blood is drawn from the body and is pumped through a membrane oxygenator, where it is exposed to a gas mixture (usually containing a high concentration of oxygen) across a synthetic membrane. This allows oxygen to diffuse into the blood while carbon dioxide diffuses out, effectively providing respiratory support without relying on the patient's lungs.

The mechanism of gas exchange in ECMO is fundamentally different from direct oxygenation through the lungs, as the ECMO circuit bypasses the pulmonary system. It also differs from passive diffusion in the alveolar sacs, which involves natural respiratory processes that may be impaired in patients requiring ECMO. Additionally, while there are chemical reactions that occur in the bloodstream, such as hemoglobin binding oxygen, the primary method of gas exchange in ECMO is through the mechanical oxygenation process facilitated by the oxygenator. This allows for efficient management of severe cases of respiratory or cardiac failure, illustrating why extracorporeal blood oxygenation is the correct choice.