The American Society of Anesthesiology practice guidelines for the management of the difficult airway describe invasive (surgical or percutaneous tracheostomy/ cricothyrotomy) and noninvasive (laryngeal mask airway, fiberoptic intubation, light wand, retrograde intubation (RI), and blind intubation) techniques to secure a known or potentially difficult airway (1). Anesthesiology residents are therefore commonly taught many noninvasive techniques described in the American Society of Anesthesiology practice guidelines. Increasingly, this occurs during a formalized “airway rotation” where appropriate techniques are demonstrated and practiced on awake, sedated, or anesthetized patients.
Conversely, experience with invasive airway procedures is difficult to obtain. The reasons for this are likely twofold. First, there undoubtedly is a reluctance on the part of anesthesiology faculty to use these techniques in an elective setting. Second, elective surgical or percutaneous cricothyrotomy (PC) would be obvious ethical misconduct. To overcome these limitations in training residents, mannequins and simulators have been developed for educational instruction in invasive airway access. We hypothesized that the use of preserved cadavers to demonstrate PC, RI, and fiberoptic bronchoscopy (FOB) would improve anesthesiology residents' confidence with these advanced airway techniques as demonstrated by an increase in the number of residents who report that they would use these techniques after an educational workshop.
After IRB approval, we performed a prospective investigation (using survey instruments) on anesthesiology residents training in PC, RI, and FOB using embalmed cadavers.
All anesthesiology residents training at the University of Kentucky Chandler Medical Center, if assigned to the anesthesiology service, are expected to attend the daily lecture as part of their residency training. In November 2005, one of the daily resident lectures was used to demonstrate these invasive airway techniques in the College of Medicine's Human Cadaver Lab.
The workshop consisted of three stations with one technique, PC, RI, or FOB, demonstrated at each station. All residents were cycled through all three stations during the daily lectures, and each station consisted of one anatomically embalmed cadaver, one instructor, and six residents.
PC was demonstrated with the contents of the Melker Cuffed Emergency Cricothyrotomy Catheter Set (Cook Critical Care, Bloomington, IN). The 18-gauge introducer needle was attached to the 5-mL syringe and other supplies, including the guidewire, scalpel, and curved dilator, and airway catheter were prepared. After the cadaver's head, neck, and chest were exposed, the cricothyroid space was identified. The introducer needle was inserted in a caudal direction into this space and advanced until air was aspirated into the catheter. The syringe was removed, and the guidewire was advanced through the introducer needle. After the guidewire was passed, the needle was removed, a small skin incision was made, and the dilator/airway catheter was passed over the guidewire. The guidewire and dilator were then removed, and the airway catheter was left in place as successful completion of PC.
RI was demonstrated with the contents of the Cook Retrograde Intubation Set (Cook Critical Care, Bloomington, IN). The 18-gauge introducer needle was attached to the 5-mL syringe and other supplies, including the guidewire, needle holder, guiding catheter, and endotracheal tube were prepared. After the cadaver's head, neck, and chest were exposed, the cricothyroid space was identified. The introducer needle was inserted in a cephalad direction into this space and advanced until air was aspirated into the catheter. The syringe was removed, and the guidewire was advanced through the introducer needle until it was visible in the cadaver's oropharynx. The guidewire was then brought out of the cadaver's mouth, and the needle holder was placed on the guidewire at the point of skin incision. The guiding catheter was inserted into the trachea over the guidewire via the oropharynx, and the endotracheal tube was placed over this guiding catheter. The guiding catheter and the guidewire were then removed, and the endotracheal tube was left in place as successful completion of retrograde intubation.
FOB was demonstrated using an Olympus Standard Intubating Fiberscope (Olympus, Orangeburg, NY). After an endotracheal tube had been placed over the flexible bronchoscope, the bronchoscope was introduced into the oropharynx. At the request of the bronchoscopist, a jaw thrust and/or tongue lift was performed. The vocal cords, the tracheal cartilaginous rings, and then the carina were identified before the endotracheal tube was advanced into the trachea. The bronchoscope was then used to confirm proper placement of the endotracheal tube.
All participants were asked to complete a survey before and after the workshop; however, completion of the surveys was not a requirement for participation in the workshop. χ2 statistical analysis was then performed on all survey data.
Eighteen residents (of 20 assigned to the anesthesiology service [90%]) attended the workshop, three PGY-1, three PGY-2, five PGY-3, and seven PGY-4. All PGY-1 residents had spent approximately 5 mo on anesthesia rotations, and all of the PGY-4 residents and two of the PGY-3 residents had spent 1 mo on the Advanced Airway Management Rotation. All 18 residents voluntarily and confidentially agreed to take part in this educational methodology research.
No residents reported that they would use PC (Table 1) before the workshop. After the workshop, significantly more residents (14 [78%], P ≤ 0.001) reported that they would use PC during future “cannot ventilate, cannot intubate” (CVCI) clinical situations. Additionally, there was a significant increase in the number of residents (from 3 [17%] to 17 [95%], P ≤ 0.001) who reported that they could use this technique correctly after the workshop.
For RI (Table 1), only one resident (6%) reported confidence using this technique during CVCI situations before the workshop; however, this increased to 12 residents (67%, P ≤ 0.001) who would use this technique during future CVCI situations. Additionally, the number of residents who reported that they could correctly use RI after the workshop increased from 5 (28%) to 15 (83%) (P ≤ 0.001).
All 18 residents reported that they had some prior experience with FOB, and 11 (61%, P ≤ 0.1) reported that they would use the technique in CVCI situations before the workshop (see Table 1). There was a nonstatistically significant increase to 16 residents (89%, P ≤ 0.1) in the number of residents who would use FOB during future CVCI situations. All residents reported that they had previously used this device correctly.
Previously, cadaveric models have been used to demonstrate invasive medical procedures, including central, saphenous, and intraosseous venous access (2,3), tube thoracostomy (2,4), and surgical cricothyrotomy (2). We are the first, however, to report data from anesthesiology residents trained to use advanced airway access techniques using embalmed cadavers.
The ethics of using cadavers to train medical students and residents in airway management is controversial and has been discussed in several articles and editorials in the medical literature (5–9). These ethical concerns, however, deal with cadavers recently deceased in locations within the hospital (medical and surgical wards, emergency rooms, and intensive care units) (10). These cadavers had not been specifically donated for medical education or research, and consent for their use had not been obtained from the recently deceased patients or their families. In contrast to these situations, the cadavers used for this educational research were specifically donated to the University of Kentucky Body Bequeathal Program, and permission for the educational workshop was obtained from the appropriate program administrators.
Of interest to many university-based training programs, the use of preserved cadavers for these educational purposes may be a cost-effective method for educating anesthesiology residents. The high cost of simulators and mannequins, for example, may be a barrier to their use during anesthesiology residency. In our department, the Human Patient Simulator™ (METI, Sarasota, FL) and the Airman™ (Laerdal, Stavanger, Norway) have also been traditionally used for airway education; however, because of the expense in purchasing and maintaining these tools, they are kept behind locked doors and accessed only with special permission. Conversely, preserved cadavers are available throughout the year in our anatomy laboratory, and there is no additional expense to clinical departments or the hospital to access them.
The use of preserved human cadavers as a simulator model, however, is limited by the inability to reproduce hemorrhage, muscle spasm, or hematoma formation (2,11). Additionally, decreased joint and tissue mobility in the preserved cadaver prevents completely realistic replication of the clinical situation. In particular, FOB was difficult with these cadavers because of the inability to move the tongue, jaw, and neck. Because fiberoptic intubation has become a standard technique available to anesthesiologists for securing the airway, early introduction to the technique in a laboratory setting would seem to have educational value. In the future, we will use unpreserved donated cadavers for advanced airway training in an attempt to find more realistic models for training.
In conclusion, our data demonstrate that using cadaver models to train anesthesiology residents in PC and RI significantly improves residents' confidence and may increase the use of these techniques during the management of emergent difficult airway situations. Additional research should be conducted to validate the idea that cadaver models improve residents' ability to use these techniques for the management of the difficult airway.
Special thanks to Ronald Newman, DO and Randall Schell, MD for assistance with the workshop. Also, thanks to Gary Ginn, Coordinator, University of Kentucky Body Bequeathal Program and the Department of Anatomy and Neurobiology for technical assistance with the cadavers used during the workshop.
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