What is the Veno-Venous (VV) Extracorporeal Membrane Oxygenation (ECMO) circuit?

From the Guidelines

Venovenous extracorporeal membrane oxygenation (VV ECMO) is a high blood flow extracorporeal circuit that provides full or partial extracorporeal pulmonary support by draining blood from the venae cavae via a femoral venous or right internal jugular venous cannula, pumping it through a membrane oxygenator, and returning it to the venous system. The VV ECMO circuit consists of several key components working together to oxygenate blood outside the body, as described in the position paper for the organization of extracorporeal membrane oxygenation programs for acute respiratory failure in adult patients 1.

Key Components of VV ECMO Circuit

• Blood is withdrawn from the venous system through a large-bore cannula typically placed in the femoral or internal jugular vein
• The blood then passes through a centrifugal pump that generates continuous flow at rates adjusted based on patient needs
• The blood travels through an oxygenator (membrane lung) where oxygen is added and carbon dioxide is removed
• The newly oxygenated blood is returned to the patient through a return cannula, usually positioned in the internal jugular vein or another large central vein
• The circuit includes a heat exchanger to maintain blood temperature and various monitoring devices that measure pressure, flow, and oxygen saturation The effectiveness of VV ECMO depends on proper cannula positioning, adequate flow rates, and appropriate ventilator management, allowing the native lungs to rest and heal while maintaining adequate oxygenation and ventilation, particularly beneficial in conditions like severe ARDS, pneumonia, or as a bridge to lung transplantation 1.

Clinical Considerations

• Anticoagulation, typically with unfractionated heparin, is essential to prevent circuit thrombosis
• Neurological monitoring and management are crucial for adult ECMO patients, as they are at risk of acute brain injury (ABI) 1
• A protocolized neurological monitoring and management approach can improve the detection and care of ABI in ECMO patients 1

From the Research

Veno-Venous (VV) Extracorporeal Membrane Oxygenation (ECMO) Circuit

The VV ECMO circuit is a form of mechanical life support that provides full respiratory bypass in patients with severe respiratory failure as a bridge to recovery or lung transplantation 2.

Key Components and Functionality

• The circuit usually includes the cannulation of two vessels (double cannulation) in its classic configuration, but the use of a single cannula is now possible for VV-ECMO support 3.
• VV-ECMO provides an artificial mechanism for oxygenation and decarboxylation of native blood, allowing for an environment in which safer mechanical ventilatory care may be provided 2.
• The circuit can be modified to improve venous drainage and/or optimize systemic hemodynamics/oxygenation, such as the addition of a third or fourth ECMO cannula 4.

Clinical Applications

• VV-ECMO is used to manage severe respiratory failure, including acute respiratory distress syndrome 5, 6.
• It is also used to avoid further lung injury (ergotrauma) in patients with severe respiratory failure 6.
• The use of VV-ECMO has expanded over the years, increasing its availability, and landmark clinical trials have provided a framework for better understanding patient selection criteria, resource utilization, and outcomes associated with ECMO 2.