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Physiology and Pathophysiology 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 Pathophysiology flashcards as text

  1. During VV-ECMO, a patient's PaO2 remains low despite adequate circuit flow. What is the most likely cause?

    Answer: High recirculation fraction

    High recirculation occurs when oxygenated blood returning from the circuit is immediately re-entrained by the drainage cannula, reducing effective oxygen delivery to the patient.

  2. Which hemodynamic effect distinguishes VA-ECMO from VV-ECMO in cardiogenic shock?

    Answer: VA-ECMO provides systemic perfusion pressure support while VV-ECMO does not

    VA-ECMO directly bypasses the heart and lungs, providing mechanical circulatory support and augmenting systemic arterial pressure, whereas VV-ECMO only supports gas exchange.

  3. What is the physiological consequence of 'North-South syndrome' (Harlequin syndrome) in femoral VA-ECMO?

    Answer: Upper body receives poorly oxygenated blood from the native failing heart while lower body receives oxygenated ECMO blood

    In femoral VA-ECMO, oxygenated retrograde ECMO flow may not reach the upper body if the recovering heart ejects deoxygenated blood antegrade, creating a watershed zone of hypoxemia in the upper extremities and brain.

  4. How does increased ECMO pump speed affect left ventricular (LV) wall stress in VA-ECMO?

    Answer: Increases LV wall stress by increasing afterload via elevated aortic pressure

    Higher VA-ECMO flows increase mean arterial pressure retrograde into the aorta, elevating LV afterload and potentially worsening LV distension if the ventricle cannot eject against the increased pressure.

  5. In a patient on VV-ECMO, the sweep gas FiO2 is increased from 0.6 to 1.0 with minimal change in patient PaO2. What does this suggest?

    Answer: Recirculation or inadequate ECMO blood flow relative to cardiac output

    When increasing oxygenator FiO2 has little effect on systemic oxygenation, insufficient ECMO flow relative to native cardiac output means a large fraction of venous blood bypasses the circuit entirely.

  6. What is the primary determinant of CO2 removal on ECMO?

    Answer: Sweep gas flow rate

    CO2 removal is primarily governed by sweep gas flow rate because CO2 diffuses readily across the membrane, and higher sweep flows increase the concentration gradient driving CO2 out of the blood.

  7. Which pathophysiological mechanism explains why patients in refractory hypoxemic respiratory failure develop pulmonary hypertension that may necessitate ECMO?

    Answer: Hypoxic pulmonary vasoconstriction causing increased right ventricular afterload

    Hypoxic pulmonary vasoconstriction is a protective reflex that diverts blood from poorly ventilated lung regions, but when hypoxemia is diffuse it causes global pulmonary vasoconstriction, dramatically increasing right ventricular afterload.