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ECMO SIMULATION

Sponsored by: Rady Children's Hospital

What is ECMO, and why do we clinicians need an ECMO simulation?

ECMO (extracorporeal membrane oxygenation) is a life-saving technique that mimics the natural function of the heart and lungs, allowing an infant, child or adult to rest while natural healing of the affected organs takes place. 

The ECMO procedure involves channeling the patient's blood into a roller pump that serves as the child's "heart" throughout treatment. The pump sends the blood through an oxygenator, which serves as an artificial lung, infusing the blood with oxygen and removing carbon dioxide and returning it to the patient. The procedure is rare and high risk, so it is crucial to keep doctors familiar with the procedure by creating a simulation.

Existing Simulation

As you may notice in the above figures, the existing simulation is limited in its resembles anatomical features. Through observation & discussions with the clinical team, it became apparent that the existing simulation fails to:

• Mimic the correct geometrical dimensions of the vasculature (veins & artery). 

• Account for the sternocleidomastoid muscle.

• Keep the skin layers in tension.

• Tissue consistency. 

• Simulate accurate blood flow pressure.

Project Goals

From this standpoint, the goals of our project focus on obtaining realism and anatomical accuracy, primarily:

• Vasculature (vein and artery) correct dimensions and wall-thickness 

• Tissue surrounding the vasculature, including a simulated sternocleidomastoid muscle

• Blood, both the texture and color of skin

• The skin on top of the tissue

• Blood flow & pressure

Additionally, the simulation must be:

• Easily manufactured, set up, and operated by non-engineering personnel.

• Cost-effective, so this system can be repeated by other hospitals with minimal resources.

Current Design

The current design is comprised of:

• A neck collar, which has a rigid 3D printed box filled with the tissue and is secured to the mannequin's neck with velcro straps.

• Tissue, inside the neck collar, with layers that simulate 

  • flesh (gelatin)

  • muscle (silicone caulking)

  • skin (silicone)

• Tubing to simulate vein and artery, with appropriate diameter and wall thickness (silicone rubber)

• Blood running through the vein and artery (glycerin with food coloring)

• A pressure delivery system, which includes a pump, simple tubing & fittings to connect to the vein and artery, a reservoir with the blood, and a bypass to prevent pressure build-up when the vein and artery are sutchered closed.

*main components highlighted

High level overview of final design: Design includes a blood pump system, skin, muscle, tissue, and vasculature.

The pressure delivery system tested with the mannequin: The pump, blood, and tubing all successfully pump the blood through the smaller tubing that simulates the vein and artery. The is a bypass, visible in the bottom of the left image, which prevents pressure build-up when the main line is closed. Right, a surgeon cuts into the artery to test the pressure, which was a little too high. We have inserted a flow control valve after the bypass to adjust the pressure appropriately.

A surgeon testing prototypes of skin (left) and muscle (right): We got feedback from surgeons on the look and feel of multiple types of skin and muscle, made with different materials and/or manufacturing methods.

The modified newborn mannequin: In order to make the top of the skin layer flush with the mannequin, we cut a hole into the hard plastic inner structure of the mannequin. The neck collar, now with a circular box design, can be placed into the cutout and secured around the neck with velcro straps.

The improved blood: Our first iteration used a recipe with corn syrup to get the right viscosity, but we were concerned about food products spoiling if the blood were made in advance and stored. This improved recipe uses glycerin to get the same thick, slimy texture, and red food coloring to make it deep red.