CES ECMO Physiology & Gas Exchange 2

Question 1

The 'Harlequin' (North-South) syndrome in femoral VA-ECMO occurs when:

Accepted Answer

The upper body receives desaturated native cardiac output while the lower body receives oxygenated ECMO blood

Answer

When the native heart partially recovers and ejects desaturated blood, the coronary arteries and brain may receive poorly oxygenated blood while the ECMO return site (femoral artery) perfuses the lower body with well-oxygenated blood.

Question 2

In VV-ECMO, which factor most directly determines the patient's cardiac output?

Accepted Answer

The patient's own intrinsic cardiac function and vascular tone

Answer

VV-ECMO does not provide direct cardiac support; the patient's native cardiac output depends entirely on their own myocardial function and loading conditions.

Question 3

A progressively decreasing pre-membrane to post-membrane PO2 gradient in the oxygenator over several days suggests:

Accepted Answer

Progressive membrane lung failure or clotting reducing gas transfer

Answer

A falling transmembrane PO2 gradient indicates the oxygenator is becoming less efficient, often due to fibrin/thrombus deposition reducing the effective gas-exchange surface.

Question 4

In ECMO, carbon dioxide clearance is most directly controlled by adjusting:

Accepted Answer

Sweep gas flow rate

Answer

CO2 removal is highly sensitive to sweep gas flow rate; increasing sweep gas increases the CO2 gradient across the membrane, enhancing clearance.

Question 5

Transmembrane pressure (TMP) across the ECMO oxygenator is monitored primarily to detect:

Accepted Answer

Clot formation or membrane failure increasing resistance within the oxygenator

Answer

A rising TMP indicates increased resistance across the oxygenator, often due to thrombus formation, signaling the need for oxygenator replacement.

CES - Certified ECMO Specialist Practice Test

CES - Certified ECMO Specialist Practice Test

CES ECMO Physiology & Gas Exchange 2