ECMO Physiology and Principles 2

Question 1

During VV-ECMO, what is the primary determinant of oxygen delivery to the patient's tissues?

Accepted Answer

Native cardiac output

Answer

In VV-ECMO, oxygen delivery to tissues depends on native cardiac output because the oxygenated blood returning from the ECMO circuit must be pumped by the patient's own heart.

Question 2

Which physical property of the oxygenator membrane determines CO2 removal efficiency in ECMO?

Accepted Answer

Sweep gas flow rate

Answer

CO2 removal is primarily controlled by sweep gas flow rate, as CO2 diffuses readily across the membrane and is 'washed out' by the gas flow.

Question 3

What is the effect of hypothermia on oxygen-hemoglobin dissociation during ECMO?

Accepted Answer

Shifts curve leftward, increasing hemoglobin O2 affinity

Answer

Hypothermia shifts the oxyhemoglobin dissociation curve to the left, increasing hemoglobin's affinity for oxygen and impairing tissue O2 delivery.

Question 4

In VA-ECMO, retrograde aortic flow from a femoral arterial cannula creates a 'mixing zone.' What determines where this zone is located?

Accepted Answer

Balance between native cardiac output and ECMO pump flow

Answer

The mixing zone (where oxygenated ECMO blood meets desaturated native cardiac output) is determined by the balance between anterograde native cardiac flow and retrograde ECMO flow.

Question 5

What is 'Harlequin syndrome' (differential hypoxia) in the context of VA-ECMO?

Accepted Answer

Upper body hypoxia while lower body is well-oxygenated due to competing blood flows

Answer

Harlequin syndrome occurs when the native heart ejects desaturated blood that perfuses the upper body while the ECMO circuit oxygenates lower body blood, creating differential oxygenation.

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO Physiology and Principles 2