ECMO Foundations of ECMO and ECMO Management 4 — Questions and Answers
Question 1: A centrifugal pump used in modern ECMO circuits generates flow primarily through:
- Roller compression of the tubing
- Electromagnetic induction creating a rotating magnetic field
- Impeller or cone rotation creating centrifugal force (Correct answer)
- Piston-driven positive displacement
Correct answer: Impeller or cone rotation creating centrifugal force
Centrifugal ECMO pumps use a rapidly spinning impeller or cone that imparts kinetic energy to blood through centrifugal force, generating flow.
Question 2: When ECMO pump RPM is increased but flow does not increase proportionally, the most likely cause is:
- Pump head thrombosis or increased circuit resistance (Correct answer)
- Excessive anticoagulation causing vasodilation
- Oxygenator membrane rupture
- Venous cannula tip in the right ventricle
Correct answer: Pump head thrombosis or increased circuit resistance
Increased RPM without proportional flow increase suggests elevated circuit resistance, often from clot formation in the pump head or oxygenator.
Question 3: In neonatal ECMO for meconium aspiration syndrome, which mode is typically preferred as first-line?
- VA-ECMO via femoral vessels
- VV-ECMO via a dual-lumen jugular cannula
- VA-ECMO via carotid artery and jugular vein (Correct answer)
- VAV-ECMO via umbilical vessels
Correct answer: VA-ECMO via carotid artery and jugular vein
Neonatal VA-ECMO via the right common carotid artery and right internal jugular vein is the standard approach because neonatal vessels are too small for suitable VV-ECMO cannulas.
Question 4: The primary purpose of a 'lung rest' strategy during VV-ECMO for severe ARDS is to:
- Maximize tidal volume to prevent atelectasis
- Apply ultra-protective ventilation settings to minimize ventilator-induced lung injury (Correct answer)
- Wean sweep gas to allow CO2 retention
- Increase respiratory rate to match native ECMO gas exchange
Correct answer: Apply ultra-protective ventilation settings to minimize ventilator-induced lung injury
Lung rest on VV-ECMO allows extreme reduction in mechanical ventilation parameters (low tidal volumes, low pressures, low rates) to minimize ongoing ventilator-induced lung injury.
Question 5: Left ventricular distension (LV dilation) during VA-ECMO is most commonly managed by:
- Increasing ECMO pump speed
- LV venting via an Impella device or atrial septostomy (Correct answer)
- Reducing sweep gas flow
- Repositioning the arterial return cannula
Correct answer: LV venting via an Impella device or atrial septostomy
LV venting with an Impella or atrial septostomy decompresses the distended LV, reduces wall stress, and may improve myocardial recovery.
Question 6: Which circuit component is responsible for actively controlling temperature of blood returned to the patient?
- Bladder reservoir
- Heat exchanger integrated into the oxygenator (Correct answer)
- Centrifugal pump head
- Pre-pump tubing clamps
Correct answer: Heat exchanger integrated into the oxygenator
The heat exchanger, typically incorporated within the ECMO oxygenator, uses water from a heater-cooler unit to regulate the temperature of blood passing through the circuit.
Question 7: During an ECMO circuit emergency requiring hand cranking the pump, the clinician must ensure:
- Sweep gas is turned off immediately
- Adequate RPM is maintained to prevent retrograde blood flow (Correct answer)
- The arterial cannula is clamped
- The oxygenator is bypassed
Correct answer: Adequate RPM is maintained to prevent retrograde blood flow
During manual hand cranking, sufficient rotational speed must be maintained because centrifugal pumps are non-occlusive and can allow retrograde flow if inadequate forward pressure is generated.
ECMO Foundations of ECMO and ECMO Management 4
A centrifugal pump used in modern ECMO circuits generates flow primarily through: