Troubleshooting: Hypoxemia:

ECMO patients have continuous oximetry monitoring, as well as frequent blood gas analysis. A decrease in SpO2 or PaO2 is a very common problem for ECMO patients. There is a slightly different approach for patients depending on whether they are on V-V or V-A ECMO. In either case, a large contribution of hypoxemia results from a mixing of oxygenated blood returning from the ECMO circuit with poorly oxygenated blood in the patient's native circulation.

  • Even though blood from the ECMO circuit is oxygen rich (e.g. PaO2 400-600 mmHg), it's oxygen saturation obviously cannot exceed 100%.
  • The dissolved oxygen measured by PaO2 does not contribute appreciably to oxygen delivery.
  • Therefore, no matter how richly oxygenated the blood is, if it mixes with a significant amount of desaturated blood, then hypoxemia will occur.
  • For example, if 2.5 L/min of blood flow with an SpO2 of 100% mixes with 2.5L/min of blood flow with an SpO2 of 70%, then the saturation of blood when it equilibrates will only be 85%.

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