CES ECMO Equipment & Technology 1 — Questions and Answers
Question 1: Which centrifugal pump design is most commonly used in modern ECMO systems?
- Roller pump with occlusive tubing
- Magnetically levitated impeller centrifugal pump (Correct answer)
- Axial flow pump
- Pneumatically driven displacement pump
Correct answer: Magnetically levitated impeller centrifugal pump
Magnetically levitated centrifugal pumps (e.g., Maquet Rotaflow, LivaNova CP5) dominate modern ECMO due to reduced hemolysis and bearing wear compared to older designs.
Question 2: What does the term 'sweep gas' refer to in an ECMO oxygenator?
- The speed at which blood flows through the circuit
- The gas (oxygen/air blend) flowing through the oxygenator membrane to facilitate gas exchange (Correct answer)
- The rate at which the centrifugal pump spins
- The priming fluid used to fill the circuit initially
Correct answer: The gas (oxygen/air blend) flowing through the oxygenator membrane to facilitate gas exchange
Sweep gas is the gas flow (typically an O2/CO2 blend) through the hollow-fiber membrane oxygenator that drives CO2 removal and sets membrane-side gas composition.
Question 3: In a hollow-fiber membrane oxygenator, which direction does CO2 most rapidly transfer?
- From sweep gas into the blood
- From blood into the sweep gas (blood to gas) (Correct answer)
- CO2 does not transfer across hollow-fiber membranes
- Bidirectionally at equal rates
Correct answer: From blood into the sweep gas (blood to gas)
CO2 moves from the blood (high partial pressure) across the hollow-fiber membrane into the sweep gas (low partial pressure) due to its high membrane diffusibility.
Question 4: The Avalon Elite bicaval dual-lumen cannula is designed for insertion via which access site?
- Femoral vein
- Right internal jugular vein (Correct answer)
- Left subclavian vein
- Femoral artery
Correct answer: Right internal jugular vein
The Avalon Elite is designed for right internal jugular vein insertion, with drainage from both the SVC and IVC and return directed toward the tricuspid valve.
Question 5: Which ECMO circuit component is responsible for maintaining circuit temperature?
- The oxygenator membrane alone
- A heat exchanger (water bath heater-cooler unit) incorporated into or alongside the oxygenator (Correct answer)
- The centrifugal pump head
- The circuit tubing material
Correct answer: A heat exchanger (water bath heater-cooler unit) incorporated into or alongside the oxygenator
A heater-cooler unit circulates temperature-controlled water through a heat exchanger adjacent to the oxygenator to regulate patient blood temperature.
Question 6: What is the primary purpose of a 'bridge connector' in an ECMO circuit?
- To connect the ECMO circuit to a hemodialysis machine
- To allow the circuit to be clamped and recirculated when the patient is briefly disconnected or during circuit changes (Correct answer)
- To connect the arterial and venous limbs to bypass the pump
- To regulate anticoagulant delivery into the circuit
Correct answer: To allow the circuit to be clamped and recirculated when the patient is briefly disconnected or during circuit changes
A bridge connector allows the circuit to recirculate when the patient limbs are clamped, maintaining circuit patency and preventing stasis/clotting during brief interventions.
CES ECMO Equipment & Technology 1
Which centrifugal pump design is most commonly used in modern ECMO systems?