Manufacture of a Multi-Purpose Low-Cost Animal Bench-Model for Teaching Tracheostomy

Summary

This article illustrates every step of the manufacture of a new multi-purpose low-cost animal bench-model for subglottic airway access management. All the procedures are shown in the video. The model's realism and its suitability for training the given clinical maneuvers were assessed by independent senior otolaryngologists and anesthesiologists.

Abstract

Tracheostomy is one of the most frequent procedures, performed through various techniques in the intensive care unit and emergency situations. Despite this, there is a lack of training on this procedure that affects its outcome, which is also dependent on operator's dexterity. Here, we take the specific training and simulation into consideration. This article aims to describe every step of the manufacture of a new multi-purpose low-cost animal bench-model, with the support of video and images, and to obtain an opinion about the quality of this model by administering a questionnaire to professionals with experience in the procedures.

Ten experts in the technique were enrolled. The model scored an average of 3.45/5 for its anatomical realism; 4.75/5 for its usefulness as a training tool for simulation courses and assessments. The time necessary to build the model was 15 minutes, and the cost amounted to 10€. The animal bench-model was considered a very useful simulator for tracheostomy training and assessments. Therefore, it could be used as a tool for medical courses and residencies.

Introduction

Difficult airway management is a critical skill for every physician dealing with critical, ill, and emergency patients. A review published in 2013 estimates that the incidence numbers of 'cannot ventilate, cannot intubate' situations with the use of surgical airway techniques vary from 0 to 18.5%¹.

Tracheostomy is one of the oldest surgical procedures and is extensively used as the method of choice for subglottic airway access for patients requiring prolonged artificial ventilation. Originally performed in the operating theater, it has become a routine practice bedside at many hospitals, especially in the intensive care unit (ICU)². Several types of techniques have been described, including surgical (ST) and percutaneous tracheostomy (PCT). Tracheostomy has been widely reported to have high complication rates.A national audit reports that 50% of airway-related deaths or brain damage in critical care are caused by tracheostomy complications³. Often, the high complication rates reflect lack of familiarity with the technique and inadequate training.

Another way to subglottically access the airways is to perform a cricothyrotomy (CT), which has been broadly recommended as a strategy to deal with 'cannot ventilate, cannot intubate'  situations in both prehospital and intra-hospital care⁴. Being a fast and potentially lifesaving fallback maneuver in the patients with a failed airway, clinicians responsible for airway management must be familiar with the technique. Practice and training therefore play a pivotal role since its success is dependent on the operator's dexterity⁵. However, due to improvements in airway management in the past decades, a decline in the need for tracheotomy and emergency surgical airways was observed. This has resulted in a lack of clinical experience and decreased exposure to this life-saving technique, which may negatively affect the quality of procedures and ultimately the safety of patients^6,7.

Nowadays, simulation is a common and effective teaching method to train medical and surgical skills, especially for novices who are learning new abilities^8,9. Simulation allows to recreate a clinical procedure or situation, providing trainees with first-hand exposure to clinical scenario and complex techniques while eliminating the risk for patients¹⁰.

A broad variety of simulators, from virtual reality to animal models, have been used in training surgical airway management^11,12,13,14. Practice on models and mannequins is reported to be the most common form of instruction for Anesthesiology and Emergency Medicine residents^15,16. Cadavers have also been used to teach neck anatomy and the procedural skills¹⁷. However, the cost of all these options are sometimes prohibitive and can pose ethical and moral constrains and challenges. Low cost simulators have also been described and suggested for educational purposes but have not been used to train all the subglottic airway access procedures.

In this manuscript, we describe how to manufacture an easily-made, low-cost and high-fidelity bench-model that simulates the human neck to perform cricothyrotomy, percutaneous and surgical tracheostomy and its evaluation. The main aim was to design an easy-to-make model with readily and regularly available materials so that anyone can simply emulate and reproduce it. The overall time to assemble the model was about 15 minutes and the cost estimate was approximately of 10€ including resources and manufacturing (20€/h).

Protocol

The animal anatomic segments, normally intended for human consumption, were purchased at a local butcher's shop ( Figure 1). Therefore, they could be easily transported and stored with no specific restrictions or sanitary regulations.

1. Cleaning the swine upper airways

1. With the help of a dissecting scalpel, Adson forceps and Metzembaum scissors, clean the trachea and larynx from excess surrounding tissues (lateral muscles, excess of tongue), by cutting and dissecting.
2. Remove tissue until the larynx cartilages are almost exposed and the tracheal rings are easy to palpate.
3. Remove the hyoid bone and surrounding soft tissues: find the eminence of the greater horn and follow the horn with the blade, then pass to the contralateral one and repeat the same operation until the whole part is removed.
4. Cut the trachea at its distal side approximatively at 15 cm from the larynx using a dissecting knife.
   NOTE: The removed part, composed by mediastinal organs, will be used for the next step in the procedure.

2. Preparing the thyroid

1. Take the previously discarded mediastinal organs and search for the thymus.
   NOTE: The thymus is usually located on the frontal portion of the mediastinum right over the right atrium. Adult pigs may have a very small thymus.
2. With dissecting forceps, detach the thymus from the surrounding tissue.
3. Carve the just obtained pig thymus into a butterfly shape to recreate a simulated thyroid.
   1. With a dissecting knife, cut a flat slice of thymus 1.5 cm thick.
   2. With Metzembaum scissors, cut the slice in a butterfly shape with two 3 cm x 2 cm lobes connected by a hystmus.
      NOTE: The overall dimensions of the thyroid should be 3 cm long, 6 cm large and 1.5cm thick.

3. Suturing the thyroid to the tracheal wall.

NOTE: For the next step, use the previously prepared upper airways and the simulated thyroid.

1. Place the simulated thyroid between the first and third tracheal ring.
2. Take a needle holder and surgical forceps. Grab a 2/0 silk suture.
3. Suture the thyroid with two lateral horizontal mattress stitches passing in each lobe and in the lateral portion of the trachea.
   NOTE: The horizontal mattress stitch wraps more tissue than the normal stitch. This is important when suturing soft tissues, as pig thymus, that tends to tear up.
4. Pass the needle only in the superficial part of the trachea to prevent the possibility of seeing the thread in the tracheal lumen if performing fibroscopy.
   NOTE: Identification and preservation of the thyroid gland avoiding postoperative bleeding represent crucial surgical steps during tracheotomy procedure.

4. Preparing the esophagus

1. Use the esophagus, which is located on the backside of the trachea, to simulate the neck fascia and muscles.
2. Remove the esophagus from its larynx connection by cutting it with a scalpel or with surgical scissors.
3. Cut and open the esophagus on its length with surgical scissors.
4. Hold the muscle and mucosa with toothed forceps to help the cutting procedure. The result of this operation will be a rectangle of muscle covered by esophagus mucosa.

5. Suturing the esophagus to the trachea

1. Place the just obtained layer of muscles on top of the trachea and larynx with the mucous membrane face up. The aim is to cover the larynx: from the thyroid cartilage summit to the last tracheal rings.
2. Suture the opened esophagus with at least 6 simple stitches:
   One on the proximal side of the model, on the summit of the Thyroid cartilage.
   One on the distal side of the preparation, on the frontal portion of the last tracheal ring.
   At least one on each side of the trachea.
   One on each side of the lower lateral portion of the thyroid cartilage where cricothyroid muscles are.
3. Mark a line on the esophagus mucosa with white India ink to simulate the linea alba.
   NOTE: Identification and proper dissection through the linea alba is an important step during tracheotomy procedure (Figure 2).
   1. To do so, use white India ink and an insulin syringe.
   2. Withdraw some ink and then track a line on the simulated fascia by scratching it with the needle while spilling little drops of ink.
   3. Remove the excess of ink gently with a small swab.

6. Preparing the foam base for the model

1. Cut a square of foam of 3 cm x 10 cm x 15 cm.
2. Shape a furrow 2.5 cm large and 10 cm long in the center of the foam.
   1. To do this, fold half of the square of foam so that it creates a longitudinal hump on one side.
   2. Cut 1 cm of the hump off all its length with scissors.
   3. Unfold the foam square and trim the just formed furrow smoothly.

7. Stapling the model to the wooden tablet

1. Take a wooden tablet of the same dimensions of the foam.
2. Place the foam square on the wooden tablet and insert the model in the foam furrow.
3. With a wood stapler, place a clip on the end of the trachea, on the remaining lateral muscles of the thyroid cartilage and on the epiglottis.

8. Preparing the skin

1. Take the pig skin collected from the butcher shop and cut it in a square shape big enough to cover the whole model. Usually, a square of 25 cm x 20 cm is sufficient.
2. Cut the skin with a dissecting knife and cover the model with it.

9. Stapling the skin to the wooden tablet

1. Take the stapler and fix the skin to the tablet with about 10-15 clips. Place them on the vertical sides of the tablet
2. Trim the excess skin on each side of the tablet with the help of a knife.
3. Use cocker forceps to firmly hold the skin to allow a safer cutting.

Results

We assessed the feasibility and acceptability of the easily-made, low-cost and high-fidelity bench-model that simulates the human neck as a tool for cricothyrotomy, percutaneous and surgical tracheostomy training. After a review of current literature about simulation in surgical education, a survey instrument was designed. The questionnaire consisted of the following content sessions:
a. general data and demographics of the participants;
b. fidelity of the bench-model;
c...

Discussion

The manufactured low-cost and high-fidelity bench-model simulated the human neck and enabled practice of cricothyrotomy, percutaneous and surgical tracheostomy. The designed survey filled by senior ENT physicians and anesthesiologists evaluated the extent to which the model replicates the physical characteristics of the neck and its suitability for training the given subglottic airway access procedures.

Several home-made models or simulators have been reported and we tried to overcome their li...

Materials

Name	Company	Catalog Number	Comments
Foam	BRICOSELF ITALIA, vercelli	na	Used to stabilyze the model on the wooden tablet
Insuline Syringe	na	na	Used to draw linea alba with india ink
Pig Esophagus	Butcher shop (Il mercato carni, di Dutto Srl. - 28100, Novara (Italy)	na	Wet material used to build the simulated muscular layers and fascia
Pig skin	Butcher shop (Il mercato carni, di Dutto Srl. - 28100, Novara (Italy)	na	Wet material used to obtain the simulated skin
Pig thymus	Butcher shop (Il mercato carni, di Dutto Srl. - 28100, Novara (Italy)	na	Wet material used to build the simulated thyroid
SILK suture - Vetsuture SILK 2/0 (Metric 3) Ago 3/8 30mm Reverse Cutting (12 pz)	Sanitalia Care Srl	SILK2CN	Sutures to tight all the parts of the model
Surgical instruments scissors, forceps, knife, needle holder	na	na	na
Swine upper airways	Butcher shop (Il mercato carni, di Dutto Srl. - 28100, Novara (Italy)	na	Wet material used to build the model
white india ink -  pelikan 10ml	Cartoleria Manzoni di Lo Monaco Rosaria s.a.s. 97019 Vittoria, Italy	36340	Ink used to mark the linea alba on the esophagus
Wood stapler	BRICOSELF ITALIA, vercelli	na	Used to staple on the model
Wooden tablet	BRICOSELF ITALIA, vercelli	na	Used to stabilyze the model with the stapler