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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.

Read the first 7 Physiology and Principles flashcards as text

  1. In VA-ECMO, how does left ventricular (LV) afterload change compared to a patient without ECMO support?

    Answer: LV afterload increases because retrograde ECMO flow opposes ventricular ejection

    Retrograde aortic flow from femoral VA-ECMO increases LV afterload, which can worsen LV distension and pulmonary edema in patients with severely impaired LV function.

  2. What does the term 'ECMO recirculation' mean, and how is it measured?

    Answer: Re-aspiration of already-oxygenated blood into the drainage cannula; estimated from SvO2 and SaO2 values

    Recirculation is the fraction of oxygenated blood returning from the ECMO circuit that is immediately re-drained before circulating through the patient, estimated using venous and arterial saturation values.

  3. Which of the following best explains why pulsatility is important to maintain during VA-ECMO support?

    Answer: Pulsatile flow preserves microvascular function and organ perfusion pressure waveforms

    Pulsatile flow maintains physiologic microvascular tone and endothelial function; prolonged non-pulsatile VA-ECMO flow is associated with end-organ dysfunction.

  4. What is the 'pressure-flow' curve concept as it applies to ECMO centrifugal pumps?

    Answer: The relationship between pump speed and resulting flow, which shifts with changes in preload and afterload

    Centrifugal pump pressure-flow curves show that at a given RPM, flow varies with inlet pressure (preload) and outlet resistance (afterload), requiring continuous flow monitoring rather than relying on RPM alone.

  5. During ECMO, what is the physiological basis for 'metabolic alkalosis' developing when citrate anticoagulation is used?

    Answer: Citrate is metabolized to bicarbonate in the liver, raising plasma pH

    Citrate is metabolized in the liver to bicarbonate, and in high doses (or with impaired liver function) can cause significant metabolic alkalosis.

  6. How does the dissolved oxygen (Henry's Law) contribute to ECMO oxygenation at very high FiO2 sweep gas settings?

    Answer: Dissolved O2 increases linearly with partial pressure, providing meaningful additional O2 delivery

    At high PaO2 values achievable via ECMO at FiO2 1.0, dissolved oxygen (0.003 mL/mmHg/dL) contributes meaningfully to total oxygen content, especially in severely anemic patients.

  7. What physiological phenomenon explains why a patient's SaO2 may improve after reducing ECMO blood flow in VV-ECMO?

    Answer: Reduced flow decreases recirculation, allowing more fresh venous blood to be oxygenated

    Paradoxically, reducing VV-ECMO flow can decrease recirculation, meaning a greater fraction of the blood processed is truly desaturated venous blood rather than already-oxygenated recirculated blood.