Easy to Implement Oral Cavity Modification to Expand simulation Based Training in Airway Management
Authors:
Niyati N Mehta, DDS, Simulation Fellow
San Francisco VA Medical Center
Shelley H Miyasaki, DDS, PhD, Chief of Oral and Maxillofacial surgery
San Francisco VA Medical Center, University of California at San Francisco
Jan Hirsch, MD, Assistant Professor of Anesthesiology
San Francisco VA Medical Center, University of California at San Francisco
Richard L Fidler, CRNA, CRNP, MSN, MBA, Simulation Director
San Francisco VA Medical Center, University of California at San Francisco
Department:
Clinical Simulation Program, San Francisco VA Medical Center
Abstract:
Introduction: Injuries to the oral cavity and teeth can occur during routine intubation and general anesthesia, but often occur in emergency situations when the priority of securing the airway supersedes pre-anesthetic evaluation. This study demonstrates the feasibility of modifying the oral cavity to increase the dental fidelity during emergency airway management.
Methods: A Laerdal® Manikin was utilized to manipulate the pre-existing Polyester (hard) and the Vinyl (flexible) dentition sets that are interchangeable among the Laerdal® family of manikins. Items easily available in a dental laboratory like dental acrylic and dental impression material were used to create modifications.
Results: Laerdal® dentition sets were altered to simulate common dental (tooth- related) trauma encountered during intubation such as a fracture, luxation or avulsion injuries. Anatomical variations like carious (decayed) teeth, loose teeth and Class II malocclusion (overbite) were also fabricated. Tooth luxation was engineered to occur with pressure by a laryngoscope and bleeding teeth were also created to demonstrate excessive pressure applied during direct laryngoscopy. It is feasible to improve the realism of the Laerdal® family of manikins with simple modifications.
Conclusions: This project proves the concept of feasibly fabricating anatomical variations to increase the fidelity of existing simulation manikins. Other anatomical variations present challenges to airway management and future research will aim at creating additional modifications. Additionally, future research will seek to quantify the improvement in airway management skills by anesthesia and emergency medicine providers by training on manikins with variable oral cavity anatomy.
Introduction:
Injuries to the oral cavity and teeth can occur during routine intubation and general anesthesia, resulting in one-third of all medico-legal claims against anesthetists.1 During endotracheal intubation, dental injuries occur up to 12% of the time, mostly credited to poor technique, unexpectedly difficult intubation and emergency situations.2 Injuries during intubation tend to occur in already diseased structures3, such as carious or periodontally involved teeth, or in patients with anatomically difficult airways. Although studies have cited the importance of pre-surgical inspection of the oral cavity and evaluation of anatomic variations,3 pre-anesthetic evaluation of the oral cavity is usually limited to the Mallampati classification and jaw protrusion which look past the dentition and focus on the oropharynx.4 Difficult airway courses also focus more on oropharyngeal, supra- and infra-glottic obstacles to managing the airway and frequently overlook the dentition as a barrier to appropriately managing the airway.
In an emergency situation, the airway typically takes priority over careful protection of the dentition,2 which may lead to dental trauma, and the possible addition of obstacles to securing the airway, like loose or broken teeth.5 Current simulators do not allow proper training of dental variation that may lead to trauma during intubation. The goal of this project was to determine the feasibility of creating simple and inexpensive dental modifications to existing manikins, thereby increasing the fidelity of difficult airway management in medical emergency simulation training.6
Methods:
Modifications of LaerdalÒ dentition sets were fabricated using items commonly found in a dental laboratory such as dental acrylic, impression material, and an electric drill. Disposable materials, such as acrylic and impression material, totaled under $40, but an electric drill can total up to $100 as a one-time investment and can be purchased at any hardware store. All modifications were completed by a CRNA and a dentist, taking about 30 minutes for each modification, and would require minimal practice to achieve mastery.
Overbite (Class II Dental Malocclusion):
Purpose: Creation of a spacer to position upper teeth forward
Manikin Modification: To simulate airway challenges accompanying patients with significant overbite
(See Figure, Supplemental Digital Content 1, which demonstrates steps for modification)
Materials:
· LaerdalÒ Vinyl dentition set
· Petroleum Jelly
· 3M™ ESPE™ Express™ STD Putty
· No. 25 surgical blade
Instructions:
1) Place the dentition set with the teeth side towards the table. Spread Petroleum Jelly in the grooves where the connection to the manikin head is made. This helps lubricate the dentition set facilitating removal of the putty.
2) Mix putty according to manufacturer protocol and separate into two balls about 0.5 inches in diameter.
3) Put each ball into the V-shaped grooves and allow putty to set up for 3 minutes.
4) To adjust the amount of maxillary protrusion, cut back the putty inserts using the No. 25 blade. Our photographs demonstrate a 0.5 inch putty insert.
Loose Tooth/Avulsing Tooth:
Purpose: Creation of a tooth that can be displaced or dislodged during airway management. This will be similar to a dentist fabricating a temporary crown.
Manikin Modification: Simulation of dental damage during airway manipulation; identification of loose teeth for pre-airway management; retrieval of dislodged teeth from the oropharynx or deeper airway.
(See Figure, Supplemental Digital Content 2, which demonstrates steps for modification
Materials:
· LaerdalÒ dentition set
· Petroleum Jelly
· 3M™ ESPE™ Express™ STD Putty
· Jet Tooth Shade TM Powder (tooth colored acrylic material)
· Dental drill (electric rotary tool like a DremelÒ) with a round burr
· Impression tray
Instructions:
1) Spread petroleum jelly on the upper teeth to help with easy removal of the putty material.
2) Mix 3M™ ESPE™ Express™ STD Putty according to manufacturer’s instructions forming a ball at least 2 inches in diameter. Roll out the putty and place in impression tray. Place dentition set teeth side down into the putty and completely cover the teeth from canine to canine making sure to extend the putty past the teeth and onto the pink gingival area. Allow putty to set up for 3 minutes and remove carefully. This will make an impression of the unaltered dentition set.
3) The maxillary left central incisor (left front tooth) will then be removed with an electric hand-piece (dental drill) or #25 blade. Using a round burr, slowly remove tooth structure leaving the adjacent teeth and the gingiva above the maxillary left central incisor intact.
4) Drill a 3mm diameter hole in the missing tooth site to allow for the post space of the tooth that will be fabricated.
5) Spread Petroleum Jelly on the dentition set again and in the 3mm hole that was created.
6) Mix Jet Tooth Shade TM Powder according to manufacturer recommendations and place in the impression where the maxillary left central incisor is positioned. Then place the dentition set into the putty impression; this will form the tooth.
7) After 5 minutes of drying time, the tooth will be retrieved from the putty mold and trimmed using an electric hand-piece (dental drill). Try to remove excess acrylic allowing the shape of the tooth to mimic the tooth that was removed.
Loose Tooth/Avulsing Tooth with added Bleeding feature (SimMan3G or SimMan Essential with bleeding function):
Purpose: Creation of a tooth that can be displaced or dislodged and subsequently will bleed during airway management
Manikin Modification: Simulation of dental damage during airway manipulation to increase the fidelity of the dislodged tooth by adding the bleeding feature
(See Figure, Supplemental Digital Content 3, which demonstrates steps for modification
Materials:
· LaerdalÒ dentition set
· Petroleum Jelly
· 3M™ ESPE™ Express™ STD Putty
· Jet Tooth Shade TM Powder (tooth colored acrylic material)
· Dental drill (electric rotary tool like a DremelÒ) with round burr
· Left shoulder port tubing
· Guide wire
· 19 gauge 1-inch needle
· Hemostat
Instructions:
Follow steps 1-7 under Loose tooth/avulsing tooth
8) Attach the bleeding port tubing to the left shoulder port of the LaerdalÒ manikin, which will be re-routed through the manikin head. Unzip the neck and head skins for access to the inner-head. Push a 19 gauge 1-inch needle from the inside of the mouth near the back left upper molar area into the inner-head; this will create a channel between the mouth and inner-head.
9) Using a guide wire, run it through the inner-head and out the mouth through the needle. Remove the needle and dispose in the sharps container. Thread the left shoulder port tubing around the guide wire and using a hemostat pull the tubing through the cheek fold.
10) The tubing should then be inserted into the back side of the dentition set where the 3mm diameter was made and the tooth will then be inserted back into the dentition set. The bleeding function is activated via the instructor module.
Long incisors:
Purpose: Creation of long maxillary incisors
Manikin Modification: To simulate airway challenges accompanying patients with large dentition that can obstruct the view of the airway
(See Figure, Supplemental Digital Content 4, which demonstrates steps for modification
Materials:
· LaerdalÒ dentition set
· Filtek™ Supreme Ultra Flowable Restorative Resin
· Kerr Optibond Solo Plus
· Microbrushâ Tube Series Applicators
· Dental Curing light
Instructions:
1) Apply Optibond Solo Plus on the incisal edges of the teeth you want to elongate with a microbrush. This will enable the resin/composite to attach to the dentition set.
2) Light Cure for 20 seconds.
3) Flow resin material onto the incisal edges to the desired length.
4) Light Cure for 40 seconds.
5) Recommend doing one tooth at a time and curing while adding to avoid material spreading all around teeth.
Carious teeth:
Purpose: Creation of diseased tooth structure
Manikin Modification: To simulate airway challenges accompanying patients with decayed and broken down teeth that have the potential to break and fall in the airway.
Materials:
· LaerdalÒ (hard) dentition set
· Dental drill (electric rotary tool like a DremelÒ) with round burr
· Permanent marker (black/red)
Instructions:
1) Using a dental drill with a round burr, drill a large hole into the palatal side of the maxillary central incisor (or any tooth you want to have a cavity). This will act to weaken the tooth and to make it more translucent.
2) Using permanent marker, color the inside of the tooth with red and black permanent marker.
3) You can do this to as many teeth as you want.
Results:
We proposed and implemented the ability to fabricate several modifications including the following: Overbite, Loose tooth, Bleeding tooth, Long incisors, and carious teeth. The following pictures show the unaltered manikin vs. the manikin with the modified dentition set.
Class II Malocclusion
<Figure 1
Loose teeth/Bleeding teeth
<Figure 2
Long incisors
<Figure 3
Carious teeth
<Figure 4
Discussion:
This project demonstrates the feasibility of fabricating and implementing anatomical variations of the dentition as a means to increase the fidelity of already existing simulation manikins. Most courses training basic and difficult airway techniques focus on approaches to the trachea that are behind the tongue and above the glottis, despite the wide variety of the population having varied anatomy of the front teeth, which present the first challenge. The alterations of the existing dentition sets facilitate the simulation of real life conditions where patients have teeth in poor repair that are susceptible to injury during intubation, especially in emergency situations where pre-assessment cannot be performed. Providers from respiratory therapy, anesthesia, critical care, emergency, and prehospital arenas have the potential to benefit from simulation of abnormal anatomy demonstrated by this project. These variations create obstacles to airway management found in the general population.
Simulation scenarios were conducted to test the validity of these oral cavity modifications, with participants from anesthesia, critical care, and oral surgery. Participants were not informed of the modifications, and if pre-intubation airway evaluation was performed, the dentition was ignored by most of residents. The oral surgery resident that did examine the teeth prior to intubation did make note of a loose tooth. Several successful intubations with no dental trauma occurred as well as several intubations when only minor luxation injuries were recorded. Avulsion injuries were observed, and the simulation of blood from the dentition lead to difficulty using a Glidescope® for intubation. If the tooth was dislodged, it was typically unnoticed by the intubating clinician, and in a few instances, the tooth could not be retrieved due to aspiration and subsequent simulation of decreased oxygen saturation levels lead to simulation of respiratory compromise. This data may provide insight into how to better incorporate examination of the teeth into pre-intubation evaluation and the type of brief dental evaluations that need to be performed even prior to emergency intubations.
Further modifications to the oral cavity, head and neck of the pre-existing LaerdalÒ manikins are in progress to enhance anatomical fidelity. A challenge that exists to creating a Class III Malocclusion (underbite) in currently available manikins is the mandibular dentition set is fixated to the manikin via screws, unlike the maxillary dentition set. This fixation of the mandible also prevented us from creating variations to the teeth on the mandibular dentition set. An additional challenge is that the size of both the maxilla and mandible are standardized and cannot be altered. This would be necessary to simulate micrognathia, which is common in patients with Pierre-Robin and Treacher-Collins syndrome.
To adjust mouth opening, another variation improving anatomic fidelity would be adapting the Laerdal ® software program to allow different degrees of interincisal opening. With current technology, the instructor can only switch trismus on or off which does not take into account patients that have different degrees of interincisal opening and the variation that exists between male and female patients.
Conclusion:
We proposed a number of modifications to the oral cavity of simulator manikins, and described how these modifications can be implemented in a limited time with basic materials and tools. These modifications enhance the anatomical fidelity of the airway, and expand the range of skills in routine and emergency airway management that can be trained.