TissueDB/Simulators/Cricothyrotomy Simulator (Kei)

The REAL CRIC Trainer is a low-cost open surgical cricothyrotomy task-trainer — a pork-belly slab laid over a 3D-printed trachea model — for procedure laboratories in emergency medicine, critical care, surgery, otolaryngology and anaesthesiology.^[1] The pork-belly overlay gives a realistic skin-and-landmark feel as the trainee palpates the airway and makes a scalpel incision through the skin and the cricothyroid membrane. The cricothyrotomy supplies provided to the learner are a No. 10 scalpel, a 6-0 endotracheal tube and a bougie. The 3D tracheal STL is the open-access UW Airway Collaboration model also used by the White UW Cricothyrotomy Simulator.^[2]

1. Download the open-access tracheal STL from airwaycollaboration.org/3d-cric-trainer-1/ because the UW Airway Collaboration model is the anatomical base used throughout the Kei build (Kei et al. 2019, citing Duggan et al. 2017).^[2]
2. Print the STL on a resin printer (more durable — lasts more than 100 cricothyrotomy practice sessions) or in filament (cheaper but more brittle) because Kei et al. 2019 state either is acceptable and the choice trades durability against cost.
3. Attach a 15-cm length of corrugated ventilator tubing to the distal (inferior) opening of the printed trachea with duct tape, and seal the open end of the tubing with duct tape to form the carina, because this sealed segment channels the bag-valve-mask air toward the cricothyroid-membrane incision.
4. Puncture two air vents in the corrugated tubing with a scalpel, each hole smaller than the diameter of a bougie, because these vents let the bag-valve-mask air escape as the flash-of-air cue when the membrane is cut.

1. Place an 8-0 endotracheal tube into the trachea model from the superior opening with the bevel pointing up (not visible from the cricothyroid opening) and connect the tube to a bag-valve-mask, because the BVM-to-tube-to-trachea path is what delivers the flash of air when the cricothyroid membrane is pierced.
2. Secure the trachea setup to a fluid-collection tray — the lid of a plastic storage container, a cookie tray, or an oil drip pan — with a piece of 3M Microfoam surgical tape, because the tray is the base that holds the trainer down and collects the fake blood, and the same Microfoam tape also serves as the cricothyroid membrane. If Microfoam tape is unavailable, duct tape, gaffer's tape, or 3M Tegaderm may be substituted.
3. Place a mannequin head above the trachea setup (Velcro may be used to secure the head to the tray) because it makes the trainer more realistic to use.

1. Obtain a fresh pork-belly slab with skin still attached, about 15 cm × 15 cm and 3 cm thick, from a local grocery store or meat market because this size reliably covers the printed trachea model and is the size reported by Kei et al. 2019.

1. Prepare the fake blood by injecting 10 mL of red food colouring into a 1 L bag of normal saline because this red-dyed saline both feeds the subcutaneous weal and serves as the reservoir for the IV-tubing vessel (Kei et al. 2019).
2. Inject 30 mL of the fake blood subcutaneously with an 18-gauge needle into the centre of the slab to create a midline subcutaneous weal about 5 cm long, just under the skin, immediately before the simulator is used, because this weal produces visible bleeding when the skin is incised.
3. Create a superficial tunnelled incision with a No. 10 scalpel, parallel to the skin surface and about 0.5 cm beneath it, starting at the inferior end of the slab in the midline and ending halfway up, stopping just under the weal, because this opens the track that holds the IV tubing.
4. Prepare the IV tubing by cutting it just above the first injection port and removing the roller and slide clamps (leaving the bag spike, drip chamber and tubing), spike the 1 L fake-blood bag, and slide the tubing into the incision track because the faculty member feeds blood through this tubing to simulate bleeding.

1. Place the prepared pork-belly slab over the 3D-printed trachea model with the IV-tubing side facing inferiorly, aligning the tubing beneath the planned cricothyrotomy incision, because the tubing must lie directly under the incision line for the bleeding cue to register at the correct moment.
2. Place blue surgical drapes around the model for a more realistic appearance, as shown in Kei 2019 Figure 3B.

1. Have the learner perform the cricothyrotomy incision through the pork-belly skin and the Microfoam membrane under faculty supervision because the cues must be coordinated with the learner's cut.
2. Squeeze the bag-valve-mask to create the flash of air and squeeze the fake-blood (IV) bag to control the bleeding as the scalpel cuts through the cricothyroid membrane, because together these are the distinguishing feedback cues of the REAL CRIC Trainer.
3. Confirm the learner observes a visible flash of air at the membrane incision and visible bleeding on the skin incision because these are the success-indicator cues that verify the carina, vents and subdermal tubing were correctly assembled.

1. Replace the pork-belly slab and re-inject a fresh 30 mL subcutaneous weal because the incised slab cannot be reused; setup with a new piece of pork belly takes under 5 minutes.
2. Replace the Microfoam tape over the cricothyroid-membrane location if it has been cut through because the cuttable membrane proxy must be intact at the start of each learner's attempt.

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