ECMO - Extracorporeal Membrane Oxygenation Circuit Components and Management Questions and Answers

Question 1

An adult patient on VA ECMO for cardiogenic shock has a progressively increasing pressure gradient across the oxygenator, now measured at 120 mmHg. What is the most likely cause and appropriate initial action?

Accepted Answer

Oxygenator thrombus formation; prepare for an oxygenator change-out.

Answer

A progressively rising pressure gradient (transmembrane pressure) across the oxygenator, especially a value greater than 50-100 mmHg, is a strong indicator of clot formation within the oxygenator's hollow fibers. This increases resistance to blood flow and impairs gas exchange. The appropriate action is to prepare for a circuit or oxygenator change-out to prevent further complications like pump failure or embolization.

Question 2

During routine monitoring of a patient on VV ECMO, you observe 'chatter' or visible shaking in the venous drainage line, and the ECMO flow has intermittently decreased. Which of the following is the LEAST likely cause of this issue?

Accepted Answer

Increased sweep gas flow

Answer

Chatter in the venous access line indicates access insufficiency, where the pump is trying to drain more blood than is available, causing the vein to collapse around the cannula. This can be caused by hypovolemia, excessive pump speed, or the cannula tip being positioned against a vessel wall. Sweep gas flow is related to gas exchange (CO2 removal) within the oxygenator and does not directly impact venous drainage or cause access insufficiency.

Question 3

A centrifugal pump is the most common type used in adult ECMO circuits. A key characteristic of a centrifugal pump is that its flow is:

Accepted Answer

Preload dependent and afterload sensitive

Answer

Centrifugal pumps are non-occlusive pumps. Their output (flow) is dependent on the amount of blood available to enter the pump (preload) and sensitive to the resistance it has to pump against (afterload). For example, if afterload increases (e.g., due to a kink in the return line), the flow will decrease at the same RPM setting.

Question 4

The heat exchanger is an integral component of the ECMO circuit. What is its primary physiological purpose?

Accepted Answer

To maintain patient normothermia

Answer

Blood loses a significant amount of heat as it passes through the extracorporeal circuit, which is exposed to ambient room temperature. The primary function of the heat exchanger is to warm the blood before it returns to the patient, thereby maintaining normothermia.

Question 5

Which component of the ECMO circuit is directly responsible for both oxygenating the blood and removing carbon dioxide?

Accepted Answer

Membrane oxygenator

Answer

The membrane oxygenator, also called the membrane lung, is the component that performs gas exchange. It contains a semipermeable membrane that separates the blood path from the gas path, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out, mimicking the function of the alveoli in the lungs.

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO - Extracorporeal Membrane Oxygenation Circuit Components and Management Questions and Answers