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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.

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  1. During VV-ECMO, what is the primary determinant of oxygen delivery to the patient's tissues?

    Answer: Native cardiac output

    In VV-ECMO, oxygen delivery to tissues depends on native cardiac output because the oxygenated blood returning from the ECMO circuit must be pumped by the patient's own heart.

  2. Which physical property of the oxygenator membrane determines CO2 removal efficiency in ECMO?

    Answer: Sweep gas flow rate

    CO2 removal is primarily controlled by sweep gas flow rate, as CO2 diffuses readily across the membrane and is 'washed out' by the gas flow.

  3. What is the effect of hypothermia on oxygen-hemoglobin dissociation during ECMO?

    Answer: Shifts curve leftward, increasing hemoglobin O2 affinity

    Hypothermia shifts the oxyhemoglobin dissociation curve to the left, increasing hemoglobin's affinity for oxygen and impairing tissue O2 delivery.

  4. In VA-ECMO, retrograde aortic flow from a femoral arterial cannula creates a 'mixing zone.' What determines where this zone is located?

    Answer: Balance between native cardiac output and ECMO pump flow

    The mixing zone (where oxygenated ECMO blood meets desaturated native cardiac output) is determined by the balance between anterograde native cardiac flow and retrograde ECMO flow.

  5. What is 'Harlequin syndrome' (differential hypoxia) in the context of VA-ECMO?

    Answer: Upper body hypoxia while lower body is well-oxygenated due to competing blood flows

    Harlequin syndrome occurs when the native heart ejects desaturated blood that perfuses the upper body while the ECMO circuit oxygenates lower body blood, creating differential oxygenation.

  6. How does increased ECMO blood flow affect the recirculation fraction in VV-ECMO?

    Answer: Increases recirculation as more oxygenated blood is drawn back into the circuit

    Higher ECMO flow increases recirculation because a larger volume of already-oxygenated blood returning to the right atrium is re-aspirated by the drainage cannula before reaching the pulmonary circulation.

  7. Which factor primarily determines the maximum blood flow achievable through a venous drainage cannula during ECMO?

    Answer: Cannula inner diameter and length

    The inner diameter and length of the drainage cannula create the primary resistance to flow; larger bore and shorter cannulas permit higher flow rates per Hagen-Poiseuille law.