TissueDB/Simulators/Cricothyrotomy Simulator (Kei)

The REAL CRIC Trainer is a low-cost open-surgical cricothyrotomy task-trainer for emergency-medicine and anaesthesia procedure laboratories.^[1] A pork-belly slab on a 3D-printed laryngotracheal model gives the trainee a realistic skin and landmark layer; an instructor-controlled IV-tubing "vessel" bleeds on incision, and a bag-valve-mask coupled to the trachea delivers a visible flash of air at the moment the cricothyroid membrane is cut. 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 laryngotracheal 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, Step 1, citing Duggan et al. 2017).^[1][2]
2. Print the STL on a resin printer (higher surface fidelity) or an FDM printer (lower cost) because filament type and slicing parameters are not specified in the source paper and either printer category is acceptable; PLA is an acceptable default filament for single-use or light-repeat training.
3. Inspect the printed cricothyroid-membrane gap and confirm the gap is clear and aligned because the Microfoam tape applied in Phase 2 must span a clean opening to function as a cuttable membrane proxy.

1. Place the 3D-printed laryngotracheal model on a standard airway mannequin head in supine orientation because Kei 2019 Figure 3A shows this positioning and the mannequin head provides the patient-orientation platform for the procedure.^[1]
2. Lay a strip of 3 in. (approximately 7.6 cm) 3M Microfoam surgical tape across the cricothyroid-membrane gap of the printed model to form the membrane proxy because the tape yields to a scalpel with tactile and visual feedback similar to a thin membrane (Kei et al. 2019, Methods). Duct tape, gaffer's tape, or 3M Tegaderm are named alternatives if Microfoam is unavailable.
3. Connect a bag-valve-mask to the proximal end of the 3D-printed tracheal model because the instructor will squeeze the BVM during Phase 5 to generate the flash-of-air feedback cue at the moment of membrane incision.^[1]

1. Obtain a pork-belly slab approximately 15 cm × 15 cm × 3 cm from a local grocery store because this size reliably covers the laryngotracheal anatomy and is the size reported by Kei et al. 2019 (typical retail cost approximately US$5, US 2019).^[1]

1. Prepare the fake-blood solution by adding 10 mL of red food colouring to 1 L of normal saline and mixing because this red-dyed saline simulates blood visually on incision and feeds both the subcutaneous weal and the IV-tubing reservoir (Kei et al. 2019, Methods).^[1]
2. Inject 30 mL of the fake-blood solution with an 18-gauge needle into the pork belly as a subcutaneous weal along the planned incision track because this weal produces visible bleeding when the skin is incised in Phase 5.^[1]
3. Cut a 5 cm midline longitudinal skin weal and a 0.5 cm deep subdermal cut along the incision path with a scalpel because this opens the subdermal track for IV-tubing placement without compromising the outer skin surface the learner will incise.^[1]
4. Thread a length of IV tubing into the subdermal track so that the tubing lies beneath the skin along the planned cricothyrotomy incision because the tubing acts as a simulated vessel that bleeds when the learner's incision cuts across it.^[1]
5. Connect the upstream end of the IV tubing to the 1 L normal saline (fake-blood) reservoir and hang the reservoir above the trainer because gravity feed is required to produce visible bleeding through the tubing on incision.^[1]

1. Place the prepared pork-belly slab over the 3D-printed laryngotracheal model on the mannequin head and align the IV-tubing track over the cricothyroid-membrane proxy because the tubing must be directly beneath the planned incision line for the bleeding cue to register at the correct moment.^[1]
2. Cover the assembly with surgical drapes as shown in Kei 2019 Figure 3B and leave only the intended surgical field exposed because this reproduces the occluded visual field learners encounter in live cricothyrotomy.^[1]
3. Confirm the BVM is within reach of the instructor because the instructor will squeeze the BVM during Phase 5 Functional Verification to generate the flash-of-air feedback cue.^[1]

1. Have the learner perform the cricothyrotomy incision through the pork-belly skin and the Microfoam membrane proxy and have the instructor squeeze the BVM at the moment the scalpel penetrates the Microfoam because this coordinates the visible flash-of-air cue with the membrane cut — the distinguishing feedback cue of the REAL CRIC Trainer (Kei et al. 2019, Discussion).^[1]
2. Confirm the learner observes a visible flash of air at the membrane incision because this is the primary success-indicator cue of the trainer.^[1]
3. Confirm the IV tubing bleeds visible red fluid on skin incision because this is the secondary success-indicator cue and verifies the subdermal tubing was correctly routed in Phase 3.^[1]

1. Replace the pork-belly slab between learners because the incised slab cannot be reused and fresh tissue is required for each learner's procedure.^[1]
2. Replace the Microfoam tape over the cricothyroid-membrane gap if the tape has been cut through because the cuttable membrane proxy must be intact at the start of each learner's attempt.^[1]
3. Re-inject a fresh 30 mL subcutaneous fake-blood weal into the replacement pork-belly slab because the bleeding cue requires a fresh weal for each learner.^[1]

^[1][2][7]