CCP Oxygenator & Pump Maintenance 3 — Questions and Answers
Question 1: The rated flow capacity of a centrifugal pump head is primarily determined by:
- Motor speed in RPM and impeller/cone geometry (Correct answer)
- Tubing diameter of the venous line
- Blood viscosity at 37°C
- Oxygenator fiber surface area
Correct answer: Motor speed in RPM and impeller/cone geometry
Centrifugal pump output depends on impeller or cone design and rotational speed, which together generate flow against afterload.
Question 2: Unlike roller pumps, centrifugal pumps are considered 'afterload sensitive' because:
- They require manual occlusion adjustments every hour
- Flow decreases if downstream resistance increases without RPM compensation (Correct answer)
- They cannot generate pressures above 100 mmHg
- They are calibrated to a fixed stroke volume
Correct answer: Flow decreases if downstream resistance increases without RPM compensation
Centrifugal pumps deliver less flow as arterial resistance rises unless the operator increases RPM to compensate.
Question 3: Roller pump occlusion is considered correct when:
- Arterial line pressure is ≤ 150 mmHg during steady flow
- A fluid column in the arterial line drops 1 cm per minute with rollers stopped (Correct answer)
- The tubing does not visibly deform during operation
- Outflow equals 100% of pump RPM-predicted volume
Correct answer: A fluid column in the arterial line drops 1 cm per minute with rollers stopped
The standard occlusion test uses a fluid column drop rate of ~1 cm/min to balance spallation risk against regurgitation.
Question 4: Spallation from roller pump tubing is MOST reduced by:
- Increasing roller occlusion to prevent any backflow
- Using a slightly under-occluded roller setting with biocompatible tubing (Correct answer)
- Reducing arterial line flow to under 1 L/min
- Applying silicone lubricant to the raceway
Correct answer: Using a slightly under-occluded roller setting with biocompatible tubing
Mild under-occlusion minimizes repetitive compression trauma that sheds tubing particulates into the circuit.
Question 5: During a ventricular assist procedure using a centrifugal pump, a sudden drop in flow with constant RPM and decreasing inlet pressure most likely indicates:
- Systemic vasoconstriction increasing afterload
- Venous line obstruction or hypovolemia causing inlet cavitation (Correct answer)
- Pump head thrombosis
- Arterial cannula kinking
Correct answer: Venous line obstruction or hypovolemia causing inlet cavitation
Negative inlet pressure with flow reduction signals inadequate venous return or obstruction, causing the pump to cavitate.
Question 6: What is the primary concern when a roller pump segment tubing develops a crack or pinhole during bypass?
- Decreased pump flow due to reduced tubing compliance
- Air entrainment into the arterial line causing gaseous microemboli (Correct answer)
- Electrolyte dilution from crystalloid leak
- Increased hemolysis from turbulent flow
Correct answer: Air entrainment into the arterial line causing gaseous microemboli
A breach in the pressurized arterial tubing can entrain air through the defect or cause sudden circuit failure with embolic risk.
Question 7: A perfusionist performing routine oxygenator inspection before bypass notices the fiber bundle has a slight yellowish discoloration. This most likely represents:
- Normal manufacturing pigment variation
- Lipid or plasma protein deposition from prior use indicating a reused device (Correct answer)
- Oxidative damage from high FiO2 gas blending
- Bilirubin staining from hemolysis in the prime
Correct answer: Lipid or plasma protein deposition from prior use indicating a reused device
Yellowish discoloration on fibers typically indicates proteinaceous or lipid deposits from prior blood contact, confirming the device was previously used.
CCP Oxygenator & Pump Maintenance 3
The rated flow capacity of a centrifugal pump head is primarily determined by: