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

Pump speed is too high, causing hemolysis in the circuit

Answer

The drainage cannula becomes acutely obstructed

Answer

Air embolism enters the arterial return cannula

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

ECMO pump flow rate

Answer

Sweep gas FiO2 setting

Answer

Oxygenator membrane surface area

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

Improved native lung function reducing ECMO dependence

Answer

A decrease in ECMO flow requirements

Answer

Resolution of the patient's underlying respiratory disease

Question 4

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

Accepted Answer

Sweep gas flow rate

Answer

ECMO blood flow rate (pump speed)

Answer

FDO2 (fraction of delivered oxygen in sweep gas)

Answer

Membrane oxygenator surface area alone

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

Changes in the patient's cardiac output

Answer

Changes in sweep gas composition

Answer

Patient fluid balance status

Question 6

In VA-ECMO, the presence of a pulsatile arterial waveform on the arterial line monitoring indicates:

Accepted Answer

Residual or recovering native cardiac contractility

Answer

Adequate oxygenator function

Answer

Adequate circuit anticoagulation

Answer

Circuit recirculation

Question 7

The oxygen transfer capacity of an ECMO membrane oxygenator is most directly influenced by:

Accepted Answer

Blood flow rate through the oxygenator

Answer

Patient core body temperature alone

Answer

The crystalloid volume used for circuit priming

Answer

The patient's anticoagulation level