Creating an intramuscular injection pad for the SimMan 3G

Abstract

This short report outlines the rationale, design and method of production for a thigh-mounted intramuscular (IM) pad in the thigh of a SimMan 3G manikin. The aim of this project was to create an IM injection site in the manikin’s thigh to allow simulation participants to practise administering IM injections in a safe, supported environment. After creating a prototype from a plastic bottle, a module was designed to use with the SimMan 3G. A mould of SimMan’s leg was created using plaster of Paris, and then a relief was added to this mould to create the shape required to hold the sponge. Once the mould was completed, glass reinforced plastic (GRP) was applied to create the final module. Using an electric rotary tool, a hole was cut in the SimMan’s thigh to enable the module to be fitted. The final product was waterproof, lightweight and strong. It sits discretely beneath the SimMan 3G’s leg skin enabling students to practise high-fidelity IM injections on the manikin’s leg without faculty intervention. This module is a cost-effective solution for allowing participants to practise IM injections on a manikin during healthcare simulation.

Objective

Modern high-fidelity simulators are able to imitate a wide variety of illnesses and physiological conditions. This fidelity allows participants to practice practical skills and develop clinical knowledge that can be applied when working with a human patient.¹

Li explains that simulation is important as an educational tool, as it allows for safe clinical practice without the ethical issues that come with practising a technique on a critically ill patient in an emergency.² It is, therefore, important that simulation participants can perform tasks in a realistic way, mirroring real clinical practice as far as is practical.

The Oxford Simulation Teaching and Research Centre uses the Laerdal SimMan 3G for many courses but this manikin does not have an intramuscular (IM) injection site located in the thigh. This is an important feature for educating participants in the safe use of IM drugs (eg, epinephrine in anaphylaxis). We have, therefore, designed and produced a novel IM injection pad that can be sited in the thigh of SimMan 3G.

Methods

First we attempted a simple modification: gauze was packed beneath the manikin’s leg skin and this was used as an injectable pad. This was impractical because it was not possible to insert a needle fully into the manikin’s thigh and the prominent bulge in the skin was distracting to the participants. Alternative options that permitted more realistic practice were, therefore, investigated.

The SimMan essential and SimMan 3G have an air compressor and fluid tanks located in the right thigh. However, the left thigh is hollow and only contains the cables for the pedal and popliteal pulses leaving ample space for modification. The SimMan’s left thigh comprises of four main parts:

• An upper leg shell.

• A lower leg shell that fits with the upper to make up the bulk of the thigh.

• A leg shell ‘cap’ forms the interface with SimMan’s torso.

• A metal plate and tube, which is contained within the plastic shell pieces, joins the leg to the torso and provides access for cabling.

These parts are covered by the rubber leg skin.

Prototype

The prototype was constructed from a square 1 L eye wash bottle that was cut into half to create the sponge holder (see figure 1).

Figure 1.

(A) Prototype. A plastic bottle is fixed in place in the upper leg shell using Leukoplast Sleek tape. (B) Upper leg shell with integrated glass reinforced plastic (GRP) sponge holder. The holder is held in place discreetly when covered with SimMan’s leg skin.

An electric rotary multitool was used to cut a hole in the upper leg shell allowing the bottle to be inserted. It should be noted that Laerdal’s warranty does not cover repairs for ‘any adaptation or changes to upgrade the product’.³ To retain structural integrity in the leg shell, the areas around the screws and the edges of the upper shell were avoided. The rim of the bottle was cut and folded back creating a lip to ensure that the bottle stayed in place and did not fall in to the leg cavity. The prototype was then held in place by Leucoplast Sleek tape, filled with sponge and then covered with the leg skin.

This model was effective in providing a location for intramuscular injections; however, over time the tape deteriorated and the model looked unprofessional when the skin was removed.

Final design

A literature search for suitable materials led to the conclusion that glass reinforced plastic (GRP) would be best. GRP is strong, durable, lightweight, easy to mould and waterproof. It was necessary to attend a 1-day course, which cost £150, to use GRP safely. The consumables required for manufacturing the insert cost a further £30.

The improved model was then created using GRP, and the key steps were:

1. Dismantle the leg to enable creation of a relief mould of the upper thigh shell using plaster of Paris.

2. Wrap the upper thigh shell in a 5 mm layer of silicone rubber to increase the diameter of the mould and create the space required for the GRP to be applied in layers (this ensures that the new module will be large enough to sit over the top of the SimMan’s leg shell).

3. Create a cast of the upper thigh shell by placing the leg shell into a high-sided container and then using modelling clay to seal, raise and support the leg shell. This ensures that the plaster of Paris can be poured under and around the leg shell to create an effective mould. This should then be left for a day to set and dry.

4. Create a mould for the sponge holder relief by trimming the rim of an 80 mm diameter cardboard coffee cup to fit the curve of the new thigh mould. Remove the base of the cup so that it is open at both ends.

5. Place the fitted cup in the thigh mould and seal it in place with modelling clay. Then fill the cup with plaster of Paris to a depth of approximately 30 mm (this comfortably holds the sponge without creating a bulge or dip in the leg).

6. Once the relief has set, remove the cup and sand the mould to remove sharp corners and remove any irregularities in the mould to allow for smoother applying of the GRP.

7. Three layers of Honey Wax mould release compound were applied to the plaster to prime the mould before layering on the GRP. This ensures easy release of the final product from the mould.

8. Apply topcoat to the mould first as this will become the outer layer, then wait for 1–2 hours for this to become tacky.

9. Apply three layers of GRP and leave it to cure before trimming the edges with a Stanley knife (if it is green—ie, not yet hard) or with a hacksaw or diamond wheel cutter if it has fully cured. Mask, goggles and gloves should be worn when cutting GRP.

The mould allowed for three layers of 450 g chopped strand mat (these are the glass fibres which reinforce the resin to give GRP its strength) to be applied with the resin. This created a strong insert that is thin enough to sit discretely beneath the SimMan’s left leg skin.

Once the GRP had cured, the module was removed from the mould and any rough areas were sanded down.

Next, a rotary tool was used to cut and sand a new hole in a second upper leg shell for the new injection pad to be inserted. The injection pad sits over the top of upper shell but beneath the leg skin without requiring tape to hold it in place due to the rigidity of the GRP.

Due to the drying time of the plaster mould and the GRP, production was carried out over 3 days though the actual time spent working with materials was only a few hours including clean up.

Results

The IM injection pad holder created from GRP is a significant improvement on the proof of concept. The GRP is stronger, more durable and its design means that it has required very little maintenance over its 8 months of use aside from replacing the sponge insert periodically. In its current form it has now been used several dozen times. Wear and tear of the module has been limited to minor discolouration due to contact with moisture from the sponge. The thigh skin has been used for IM injections for 3 years and may need replacing in the future but currently the damage is negligible despite being used for over 100 courses. The total cost for manufacturing this module, including training, came in at under £200.

Conclusion

The primary function and reason for this project was to enable simulation participants to practise carrying out a realistic IM injection procedure. This module successfully enables that procedure to take place safely, without a member of faculty having to step in to instruct the candidate to pretend. Participants have expressed surprise when informed that injections can be carried out and comments have been made that this adds to the realism of the simulation as well as providing practice in a safe but pressured situation. All comments relating to the module have been positive. The simple shape and design means that duplicates could be easily created, either reusing the mould created and following the method described above, or potentially using three-dimensional printing techniques to scan the current model and print it from plastic. The link https://youtu.be/Fby2qFdxWTc takes you to a video that was created showing some images of the manufacturing process as well as some short clips demonstrating the module in use (online supplemental multimedia file 1).

Data availability statement

No data are available. Data sharing is not applicable to this article as no new data were created or analysed in this study.

Ethics statements

Patient consent for publication

Not required.