Physiology and Principles Flashcards
7 cards from real ECMO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physiology and Principles flashcards as text
What is the primary mechanism by which ECMO causes hemolysis?
Answer: Shear stress from the centrifugal or roller pump mechanism
Mechanical shear stress generated by the ECMO pump (particularly at high flows or with small tubing) is the primary cause of red blood cell destruction during ECMO.
During ECMO, why is the SvO2 (mixed venous oxygen saturation) measured in the drainage limb clinically important?
Answer: It indicates adequacy of oxygen delivery relative to consumption
Low drainage-limb SvO2 indicates that tissues are extracting more oxygen than is being delivered, signaling inadequate ECMO support or increased metabolic demand.
What happens to PaCO2 when sweep gas flow is doubled while ECMO blood flow remains constant?
Answer: PaCO2 decreases, potentially causing hypocapnia
Doubling sweep gas flow dramatically increases CO2 removal, often causing significant hypocapnia, so sweep adjustments require careful monitoring of blood gas values.
In a centrifugal ECMO pump, what is the effect of an acute increase in afterload (e.g., arterial hypertension) on pump flow?
Answer: Flow decreases as the pump is sensitive to pressure changes
Unlike roller pumps, centrifugal pumps are not occlusive and their flow decreases when afterload increases, making continuous flow monitoring essential.
What is the physiological rationale for targeting a lower 'lung-protective' ventilator strategy (ultra-protective ventilation) during VV-ECMO?
Answer: ECMO assumes gas exchange, allowing the lungs to rest and potentially recover from VILI
With ECMO handling gas exchange, tidal volumes and pressures can be minimized to prevent ventilator-induced lung injury (VILI) and promote lung recovery.
How does the 'oxygen transfer capacity' of an ECMO oxygenator change over time during prolonged use?
Answer: It decreases due to plasma leak, protein deposition, and thrombus formation
Over time, plasma leakage through membrane pores, protein deposition, and thrombus formation on fibers progressively reduce the oxygenator's gas transfer efficiency.
What is the clinical significance of a sudden decrease in the pressure gradient across the ECMO oxygenator?
Answer: May signal oxygenator thrombosis or clot formation within the device
An increasing or suddenly changing transmembrane pressure gradient across the oxygenator may indicate thrombus formation, prompting urgent evaluation and possible oxygenator exchange.