CES ECMO Physiology & Gas Exchange 3

Question 1

Recirculation fraction in VV-ECMO can best be minimized by:

Accepted Answer

Optimizing cannula positioning to maximize distance between drainage and return ports

Answer

Increasing sweep gas flow rate

Answer

Reducing ECMO blood flow rate only

Answer

Increasing the FDO2 to 1.0

Question 2

During VA-ECMO, left ventricular distension may develop due to:

Accepted Answer

Increased LV afterload from ECMO arterial return that the failing ventricle cannot overcome

Answer

Excessive systemic anticoagulation causing vasodilation

Answer

Excessively low pump flow rates

Answer

High sweep gas flows causing hypocapnia and vasospasm

Question 3

Which parameter best reflects the overall adequacy of systemic oxygen delivery during ECMO support?

Accepted Answer

Mixed venous oxygen saturation (SvO2) or central venous oxygen saturation (ScvO2)

Answer

Arterial pH alone

Answer

Post-oxygenator PO2

Answer

Native lung compliance measurements

Question 4

The maximum achievable post-oxygenator blood oxygen saturation in a properly functioning ECMO oxygenator is typically:

Accepted Answer

95–100%

Answer

50–65%

Answer

70–85%

Answer

30–45%

Question 5

Persistent metabolic acidosis in an ECMO patient with adequate circuit flows and a functioning oxygenator most likely indicates:

Accepted Answer

Inadequate total oxygen delivery relative to metabolic oxygen consumption

Answer

Oxygenator membrane failure

Answer

Excessive sweep gas flow causing respiratory alkalosis compensation

Answer

Circuit clotting in the venous drainage limb only

Question 6

The primary reason for targeting higher hemoglobin levels (e.g., ≥10 g/dL) in ECMO patients compared to general ICU patients is to:

Accepted Answer

Maximize oxygen-carrying capacity and total oxygen delivery (DO2)

Answer

Prevent circuit clotting and extend oxygenator life

Answer

Maintain adequate systemic anticoagulation

Answer

Reduce recirculation fraction in VV-ECMO

Question 7

The venous drainage (pre-pump) pressure in an ECMO circuit should ideally be maintained at:

Accepted Answer

Mildly negative (approximately -20 to -80 mmHg)

Answer

Strongly positive (>+100 mmHg) to ensure adequate preload

Answer

Zero (equal to atmospheric pressure)

Answer

Strongly negative (less than -200 mmHg) to maximize flow