Which symptom indicates that the oxygenator is failing?

Decreased oxygen saturation is a critical symptom indicating that the oxygenator is failing. In the context of ECMO, the primary function of the oxygenator is to provide sufficient oxygenation to the blood while removing carbon dioxide. When the oxygenator begins to fail, it is unable to effectively exchange gases, leading to a drop in blood oxygen levels, which is reflected in decreased oxygen saturation readings.

Monitoring oxygen saturation is fundamental in managing patients on ECMO, and a significant decline in these levels signals that intervention is needed to assess and potentially replace the oxygenator. This can occur due to factors like membrane clotting, malfunctions in blood flow, or changes in the conditions within the oxygenator itself.

The remaining options do not directly indicate an issue with the oxygenator. For instance, patient responsiveness, clear breath sounds, and stable vital signs can vary based on many factors unrelated to the function of the oxygenator. Thus, while they are important parameters to monitor, they do not specifically address the immediate performance of the oxygenator, making decreased oxygen saturation the most direct indicator of its failure.