CCP Oxygenator & Pump Maintenance 2 — Questions and Answers
Question 1: Which parameter is most commonly used to assess oxygenator gas transfer efficiency during cardiopulmonary bypass?
- Transmembrane pressure gradient
- Arterial oxygen saturation and PaO2 (Correct answer)
- Sweep gas flow rate alone
- Oxygenator blood prime volume
Correct answer: Arterial oxygen saturation and PaO2
Arterial oxygen saturation and PaO2 directly reflect the oxygenator's ability to transfer oxygen into the blood.
Question 2: During CPB, a sudden increase in oxygenator inlet-to-outlet pressure gradient with no change in flow rate most likely indicates:
- Venous line obstruction
- Oxygenator fiber bundle clotting or thrombosis (Correct answer)
- Air embolism in the arterial line
- Pump head failure
Correct answer: Oxygenator fiber bundle clotting or thrombosis
Progressive clotting within the hollow-fiber bundle increases resistance and raises the transmembrane pressure gradient.
Question 3: What is the primary function of the heat exchanger integrated within a modern membrane oxygenator?
- Removing CO2 from perfusate
- Regulating patient blood temperature during bypass (Correct answer)
- Filtering microemboli from arterial blood
- Increasing oxygen partial pressure
Correct answer: Regulating patient blood temperature during bypass
The heat exchanger uses countercurrent water flow to warm or cool blood to achieve target patient temperature.
Question 4: A perfusionist notices plasma breakthrough (wet gas side) on a hollow-fiber oxygenator 4 hours into a complex case. The BEST immediate action is:
- Increase sweep gas FiO2 to 1.0
- Prepare to change the oxygenator emergently (Correct answer)
- Decrease blood flow rate by 50%
- Add heparin bolus to improve anticoagulation
Correct answer: Prepare to change the oxygenator emergently
Plasma breakthrough compromises gas exchange and risks contamination; the oxygenator must be replaced as soon as safely possible.
Question 5: Which design feature of microporous polypropylene hollow fibers makes them susceptible to plasma leakage over time?
- Excessive wall thickness reducing diffusion
- Open pores that can be wetted by plasma proteins under prolonged exposure (Correct answer)
- Hydrophilic surface coating that attracts water
- Absence of anticoagulant coating on fibers
Correct answer: Open pores that can be wetted by plasma proteins under prolonged exposure
Plasma proteins gradually wet microporous polypropylene walls, allowing liquid plasma to permeate from blood to gas side.
Question 6: When priming a membrane oxygenator, air removal is best confirmed by:
- Visually inspecting the gas outlet for bubbles
- Measuring arterial line PO2 after recirculation (Correct answer)
- Checking that prime volume equals rated priming volume
- Observing clear outflow from venous reservoir drain
Correct answer: Measuring arterial line PO2 after recirculation
Circulating prime and sampling the arterial line for dissolved oxygen confirms adequate de-airing of the fiber bundle.
Question 7: Polymethylpentene (PMP) oxygenators differ from polypropylene oxygenators primarily because PMP fibers are:
- Microporous, allowing direct gas-blood contact
- True membranes with no open pores, preventing plasma leakage (Correct answer)
- Thicker-walled with lower oxygen transfer rates
- Made from silicone rubber for flexibility
Correct answer: True membranes with no open pores, preventing plasma leakage
PMP fibers are diffusion membranes without open pores, eliminating plasma breakthrough and enabling longer safe use.
CCP Oxygenator & Pump Maintenance 2
Which parameter is most commonly used to assess oxygenator gas transfer efficiency during cardiopulmonary bypass?