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

Positioning the drainage and return cannulas far apart (e.g., femoral drainage with internal jugular return) minimizes the probability that oxygenated blood is immediately re-drained.

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

VA-ECMO increases LV afterload by returning oxygenated blood to the arterial system; a failing ventricle may be unable to eject against this elevated afterload, causing distension.

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

SvO2/ScvO2 reflects tissue oxygen extraction and is the most reliable indicator of whether total DO2 meets VO2 demands in ECMO patients.

Question 4

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

Accepted Answer

95–100%

Answer

A functioning membrane oxygenator with 100% FDO2 sweep gas should fully saturate blood passing through it, achieving post-oxygenator saturations of 95–100%.

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

When tissues consume more oxygen than is delivered, anaerobic metabolism produces lactic acid, causing metabolic acidosis despite technically adequate ECMO function.

CES - Certified ECMO Specialist Practice Test

CES - Certified ECMO Specialist Practice Test

CES ECMO Physiology & Gas Exchange 3