CES ECMO Equipment & Technology 2 — Questions and Answers
Question 1: Pre-membrane pressure (P1), post-membrane pressure (P2), and venous return pressure (P3) are used to calculate which ECMO parameter?
- Pump RPM
- Transmembrane pressure gradient (ΔP), indicating oxygenator resistance (Correct answer)
- Recirculation fraction
- Circuit oxygen delivery (DO2c)
Correct answer: Transmembrane pressure gradient (ΔP), indicating oxygenator resistance
Transmembrane pressure (ΔP = P1 − P2) reflects resistance across the oxygenator — rising ΔP indicates developing oxygenator thrombosis or fiber fouling.
Question 2: Which ECMO system feature allows simultaneous hemodialysis circuit integration?
- A built-in roller pump on the drainage line
- An inline CRRT port or circuit tap point allowing CRRT machine connection to the ECMO circuit (Correct answer)
- A specially designed dual-chamber oxygenator
- An extended bridge connector for parallel flow
Correct answer: An inline CRRT port or circuit tap point allowing CRRT machine connection to the ECMO circuit
CRRT machines can be connected to dedicated ports or tap points on the ECMO circuit, allowing concurrent renal replacement therapy without additional vascular access.
Question 3: The rated flow of an ECMO oxygenator refers to:
- The maximum blood flow the pump can generate
- The blood flow rate at which outflow blood oxygen saturation reaches 95% with inlet saturation of 65% (Correct answer)
- The maximum sweep gas flow before membrane damage
- The minimum flow required to prevent circuit thrombosis
Correct answer: The blood flow rate at which outflow blood oxygen saturation reaches 95% with inlet saturation of 65%
Oxygenator rated flow is defined as the blood flow at which outlet saturation reaches 95% given a standardized inlet saturation of 65%, indicating gas transfer efficiency.
Question 4: Why is a roller pump generally NOT preferred over centrifugal pumps for neonatal ECMO circuits today?
- Roller pumps cannot generate sufficient flow for neonates
- Roller pumps cannot generate negative pressure and require gravity drainage, but centrifugal pumps offer better flow control and safety features in modern systems (Correct answer)
- Roller pumps are incompatible with heparin-coated tubing
- Roller pumps require a larger priming volume than centrifugal pumps
Correct answer: Roller pumps cannot generate negative pressure and require gravity drainage, but centrifugal pumps offer better flow control and safety features in modern systems
While roller pumps have been used historically, centrifugal pumps offer better flow control, afterload sensitivity, and automated safety features that have made them preferred in current practice.
Question 5: What does 'biocompatible circuit coating' (e.g., heparin-bonded tubing) accomplish in ECMO?
- Eliminates the need for systemic anticoagulation entirely
- Reduces contact activation of coagulation and platelet adhesion on circuit surfaces, potentially reducing required systemic heparin (Correct answer)
- Sterilizes the circuit continuously during ECMO
- Reduces hemolysis by cooling the blood
Correct answer: Reduces contact activation of coagulation and platelet adhesion on circuit surfaces, potentially reducing required systemic heparin
Heparin or other biocompatible coatings reduce surface thrombogenicity, decreasing contact activation and platelet consumption, often allowing lower systemic heparin requirements.
Question 6: Which pressure monitor location in the ECMO circuit provides the best early warning of drainage cannula obstruction?
- Post-oxygenator pressure (P2)
- Pre-pump (venous inlet) negative pressure gauge (Correct answer)
- Arterial line pressure on the patient side
- Bridge connector pressure tap
Correct answer: Pre-pump (venous inlet) negative pressure gauge
Pre-pump (inlet/venous) pressure monitors drainage line negative pressure — increasingly negative values indicate drainage obstruction or hypovolemia.
CES ECMO Equipment & Technology 2
Pre-membrane pressure (P1), post-membrane pressure (P2), and venous return pressure (P3) are used to calculate which ECMO parameter?