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Accuracy of cricothyroidotomy performed in canine and human cadaver models during surgical skills training
Accuracy of Cricothyroidotomy Performed in Canine and Human Cadaver Models During Surgical Skills Training Mary C McCarthy, MD, FACS, Mark R Ranzinger, MD, Daniel J Nolan, BS, MC, Carie S Lambert, BA, Manuel H Castillo, MD, FACS Surgical skills training is an integral component of the Advanced Trauma Life Support (ATLS) Course. Teaching techniques are continuously reevaluated and updated. Recognition of recurring technical errors in the performance of cricothyroidotomy in canine models prompted this comparison to the performance of the procedure in human cadavers. STUDY DESIGN: Thirty-three ATLS physician students performed cricothyroidotomy in canine models. Ten flight nurses performed a bimonthly surgical skills practicum on similarly prepared animals. Neck specimens were excised, fixed, and later mapped by the investigators. Subsequent courses used human cadavers obtained through the Wright State University School of Medicine Anatomical Gift Program. Cricothyroidotomy sites were mapped in situ. RESULTS: In the canine models, 47 necks with 52 attempted cricothyroidotomies were inspected and mapped by the investigators. Four specimens had multiple tracheotomy sites: three had two and one had three. If these multiple attempts are excluded from analysis, 13 of the 43 cricothyroidotomies in the canine models were misplaced (30.2%). Cricothyroidotomy placement in human cadavers was correct in 27 of 28 attempts (96.4%). CONCLUSIONS: It is imperative that cricothyroidotomy, a high-risk procedure, be taught in an appropriate model to best prepare students to perform it in a life-saving situation. Placement accuracy in canine models is low. Alternative models for teaching this procedure should be considered. ( J Am Coll Surg 2002;195:627–629. © 2002 by the American College of Surgeons) BACKGROUND:
A standardized approach to the provision of trauma care, the Advanced Trauma Life Support (ATLS) Course, arose from the efforts of Nebraska physicians responding to the tragedy of a plane crash and the failure of local medical resources to deal with multiple trauma victims. The course was designed to meet the need for provision of consistent education in the principles of trauma care for physicians on the front lines. The American College of Surgeons (ACS) rapidly endorsed the concept of surgical leadership in the management of trauma patients,
in 1979 adopted the course, and subsequently promulgated it worldwide.1 The ATLS Course is revised every 4 years, modifying the text and skill stations to incorporate new information regarding the treatment of trauma patients. Evaluation of the teaching techniques used, and assessment of the appropriateness of interventions in trauma patient care undergo continuous reevaluation. Recertification is required every 4 years. The first priority in the treatment of the trauma patient is the establishment of an airway. If intubation fails, or is contraindicated, then a surgical airway is recommended. In the ATLS Course, the procedure is commonly practiced on a live, anesthetized animal model. Recognition of recurring technical errors in the performance of cricothyroidotomy in canine models prompted this study of the value of the canine model in teaching the procedure during the surgical skills practicum of ATLS.
No competing interests declared.
Received March 27, 2002; Revised May 30, 2002; Accepted June 3, 2002. From the Department of Surgery, Wright State University, Dayton, OH (McCarthy, Ranzinger, Lambert), the Biosciences Center, Miami Valley Hospital, Dayton, OH (Nolan), and the Department of Surgery, University of Miami, Miami, FL (Castillo). Correspondence address: Mary C McCarthy, MD, FACS, Department of Surgery, Wright State University, One Wyoming St, Suite 7000, Dayton, OH 45409.
© 2002 by the American College of Surgeons Published by Elsevier Science Inc.
627
ISSN 1072-7515/02/$21.00 PII S1072-7515(02)01337-6
628
McCarthy et al
Accuracy of Cricothyroidotomy
METHODS This study was approved by the Miami Valley Hospital Animal Care and Use Committee in compliance with the Federal Animal Welfare Act (7 USC 2131-2156) and the American College of Surgeons “Policies, Procedures, and Protocols for the Surgical Skills Practicum” of the ATLS Course.2 The laboratory animal facility is registered with the US Department of Agriculture. In this study, ATLS participants performed cricothyroidotomies on anesthetized dogs acquired from a licensed vendor. The Institutional Review Board approved the study protocol. Animals used were 40 to 50 pounds, mixed breed, and both genders. Animals were preevaluated for diseases and were found to be healthy. Human cadaver donors were obtained through Wright State University School of Medicine Anatomical Gift Program. Initial training courses used canines. But as human cadavers became more available through the program, later courses used cadavers. Flight nurses performed a bimonthly surgical skills practicum on similarly prepared animals or human cadavers. Experienced ATLS instructors taught students to perform surgical cricothyroidotomies. Initial verbal instruction was followed by direct supervision of the student’s performance of the procedure in the laboratory. The neck was placed in a neutral position, preparing the skin and making a skin incision over the cricothyroid membrane. The membrane was then incised and a hemostat inserted into the incision to spread the opening. An appropriately sized, cuffed tracheostomy tube was then inserted, directing the tube inferiorly into the trachea. The specialty and training level of the individual performing the procedure and the supervising instructor were recorded. Those individuals attending the course and conducting this procedure included surgical, anesthesiology, emergency medicine, and family practice residents and attendings. Flight nurse surgical skills laboratories were separately evaluated. Participants were not informed that the surgical specimens were part of a study or would be evaluated. On completion of the surgical skills practicum, the animals were euthanized while still under deep anesthesia. Subsequently, one of the investigators removed the tracheal specimens, dissecting them from the base of the tongue to the lower trachea several rings below any tracheotomy incisions. Specimens were preserved in formalin and a surgeon and animal technician later conducted
J Am Coll Surg
a mapping and evaluation of each neck specimen. Human tracheal specimens were mapped in situ by one of the investigators. RESULTS In the canine models, 47 necks with 52 attempted cricothyroidotomies were inspected and mapped by the investigators. Four specimens had multiple tracheotomy sites; three had two tracheotomies and one had three tracheotomies. If these multiple attempts are excluded from analysis (the instructor allowed more than one student to practice the procedure in a single animal), 13 of the 43 cricothyroidotomies were misplaced (30.2%). The most common error, in five animals, was insertion between the cricoid cartilage and the first tracheal ring. Four tracheal entry sites were through the hyoid bone, three were above or through the laryngeal ventricle, and one was placed between the first and second tracheal rings. Physician participants in the surgical skills practicum had a higher misplacement rate (12 of 33, 36.4%) than did flight nurses (1 in 10, 10%). This was most likely because the flight nurses, with between 1 and 10 years experience, had bimonthly animal procedure labs, whereas this might have been the physician’s first encounter with an animal model. There were insufficient numbers of physicians in each specialty and training level to draw any valid conclusions regarding subgroups. Cricothyroidotomies performed in human cadavers during the surgical skills practicum were correctly placed in 27 of 28 attempts (96.4%). The only error in placement was a tracheal entry site between the first and second tracheal rings. DISCUSSION Complications of establishing a surgical airway in the emergent setting are fewer when a cricothyroidotomy is performed than when a tracheostomy is performed.3 Some authors contend that the complication rate in the elective setting, even when longterm intubation is required, is lower for cricothyroidotomy, although this is controversial.4 The performance of cricothyroidotomy is uncommon, but may be life-saving. A 32% complication rate in the emergent setting has been reported.5 Incorrect site of tube placement was the most frequent error, with four of five placed through the thyrohyoid membrane. Prolonged procedure times, with potential for anoxia, unsuccessful tube placement, and hemor-
Vol. 195, No. 5, November 2002
rhage were also problematic. Laryngeal fracture with permanent dysphonia occurred in one patient. Accurate and appropriate instruction in cricothyroidotomy technique is critical. Proper surgical technique during the procedure is essential. The first listed objective of the ATLS Cricothyroidotomy Skill Station is to “allow the participant to practice and demonstrate the technique of needle cricothyroidotomy and surgical cricothyroidotomy on a live, anesthetized animal.” But, this procedure relies on the ability to “Identify the surface markings and structures to be noted when performing needle and surgical cricothyroidotomies.”6 External landmarks in the canine model are different than those in the human, and they create errors in the identification of the appropriate surgical site, even with experienced instructors. In this study, canine models were compared with human cadavers as a model for the performance of cricothyroidotomy. Thirteen of 43 (30.2%) cricothyroidotomies were misplaced in dogs. In human cadavers, placement was correct in 27 of 28 (96.4%). Animal models have frequently been used for some aspects of medical training, but differences in the anatomy of these models can create problems for appropriate application of the procedure in humans. Medical professionals learning procedures for the care of human patients must be educated on the anatomic differences of the nonhuman patient. Expert animal technical assistance or preprocedure instructor review of canine anatomy can improve the accuracy of tube placement in the canine model. Lectures and verbal instruction are effective in providing steps for procedure performance, but procedure accuracy, especially in adult learners, can only be taught through the performance of those procedures, either in a real or simulated setting. It is recommended that participants (students and instructors) be made aware of their performance through immediate postprocedure feedback. Evaluation and correction of technique is essential in teaching surgical procedures. Four types of patient models are proposed for use during the ATLS Surgical Skills Practicum: (1) live, anesthetized, nonhuman models (swine, sheep, goat, or canine); (2) human cadavers; (3) anatomic human body mannequins; and (4) nonhuman cadavers.7 The avail-
McCarthy et al
Accuracy of Cricothyroidotomy
629
ability of other models and their accuracy in representing the human body should be similarly evaluated, as in our study, before widespread implementation. In conclusion, cricothyroidotomy in the emergent setting has a lower complication rate than that of tracheostomy. It is essential that this procedure, which is life saving, but only rarely needed, be taught through an accurate method to provide the greatest benefit to patients. In our study, cricothyroidotomy in canine models was appropriately sited only 69.8% of the time; the same procedure performed in human cadavers was accurate 96.4% of the time. Improved teaching techniques can increase accuracy in animal models, but human cadavers represent a far superior model for teaching the procedure accurately on initial instruction. Newer options should be considered and similarly evaluated before widespread implementation. Author contributions
Study conception and design: McCarthy, Castillo Acquisition of data: Ranzinger, Nolan Drafting of manuscript: Ranzinger, Lambert Critical revision: McCarthy Supervision: McCarthy REFERENCES 1. Course Overview: the purpose, history, and concepts of the ATLS Program for doctors. Advanced Trauma Life Support Course for Doctors: Instructor Manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 11. 2. Section II: policies and procedures, chapter 9: policies, procedures, and protocols for the surgical skills practicum. Advanced Trauma Life Support Course for Doctors: Instructor Manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 637–662. 3. Lewis RJ. Tracheostomies: indications, timing, and complications. Clin Chest Med 1992;13:137–149. 4. Brantigan CO, Grow JB. Cricothyroidotomy: elective use in respiratory problems requiring tracheostomy. J Thorac Cardiovasc Surg 1976;71:72–81. 5. McGill J, Clinton JE, Ruiz E. Cricothyrotomy in the emergency department. Ann Emerg Med 1982;11:361–364. 6. Section I: core course content, chapter 2: airway and ventilatory management, Skills Station III: cricothyroidotomy. Advanced Trauma Life Support Course for doctors: instructor manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 89–96. 7. Parks S, Hughes I. Alternative models for the ATLS surgical skills practicum. ATLS Announcement. November 7, 2001. American College of Surgeons, Chicago, IL.
A standardized approach to the provision of trauma care, the Advanced Trauma Life Support (ATLS) Course, arose from the efforts of Nebraska physicians responding to the tragedy of a plane crash and the failure of local medical resources to deal with multiple trauma victims. The course was designed to meet the need for provision of consistent education in the principles of trauma care for physicians on the front lines. The American College of Surgeons (ACS) rapidly endorsed the concept of surgical leadership in the management of trauma patients,
in 1979 adopted the course, and subsequently promulgated it worldwide.1 The ATLS Course is revised every 4 years, modifying the text and skill stations to incorporate new information regarding the treatment of trauma patients. Evaluation of the teaching techniques used, and assessment of the appropriateness of interventions in trauma patient care undergo continuous reevaluation. Recertification is required every 4 years. The first priority in the treatment of the trauma patient is the establishment of an airway. If intubation fails, or is contraindicated, then a surgical airway is recommended. In the ATLS Course, the procedure is commonly practiced on a live, anesthetized animal model. Recognition of recurring technical errors in the performance of cricothyroidotomy in canine models prompted this study of the value of the canine model in teaching the procedure during the surgical skills practicum of ATLS.
No competing interests declared.
Received March 27, 2002; Revised May 30, 2002; Accepted June 3, 2002. From the Department of Surgery, Wright State University, Dayton, OH (McCarthy, Ranzinger, Lambert), the Biosciences Center, Miami Valley Hospital, Dayton, OH (Nolan), and the Department of Surgery, University of Miami, Miami, FL (Castillo). Correspondence address: Mary C McCarthy, MD, FACS, Department of Surgery, Wright State University, One Wyoming St, Suite 7000, Dayton, OH 45409.
© 2002 by the American College of Surgeons Published by Elsevier Science Inc.
627
ISSN 1072-7515/02/$21.00 PII S1072-7515(02)01337-6
628
McCarthy et al
Accuracy of Cricothyroidotomy
METHODS This study was approved by the Miami Valley Hospital Animal Care and Use Committee in compliance with the Federal Animal Welfare Act (7 USC 2131-2156) and the American College of Surgeons “Policies, Procedures, and Protocols for the Surgical Skills Practicum” of the ATLS Course.2 The laboratory animal facility is registered with the US Department of Agriculture. In this study, ATLS participants performed cricothyroidotomies on anesthetized dogs acquired from a licensed vendor. The Institutional Review Board approved the study protocol. Animals used were 40 to 50 pounds, mixed breed, and both genders. Animals were preevaluated for diseases and were found to be healthy. Human cadaver donors were obtained through Wright State University School of Medicine Anatomical Gift Program. Initial training courses used canines. But as human cadavers became more available through the program, later courses used cadavers. Flight nurses performed a bimonthly surgical skills practicum on similarly prepared animals or human cadavers. Experienced ATLS instructors taught students to perform surgical cricothyroidotomies. Initial verbal instruction was followed by direct supervision of the student’s performance of the procedure in the laboratory. The neck was placed in a neutral position, preparing the skin and making a skin incision over the cricothyroid membrane. The membrane was then incised and a hemostat inserted into the incision to spread the opening. An appropriately sized, cuffed tracheostomy tube was then inserted, directing the tube inferiorly into the trachea. The specialty and training level of the individual performing the procedure and the supervising instructor were recorded. Those individuals attending the course and conducting this procedure included surgical, anesthesiology, emergency medicine, and family practice residents and attendings. Flight nurse surgical skills laboratories were separately evaluated. Participants were not informed that the surgical specimens were part of a study or would be evaluated. On completion of the surgical skills practicum, the animals were euthanized while still under deep anesthesia. Subsequently, one of the investigators removed the tracheal specimens, dissecting them from the base of the tongue to the lower trachea several rings below any tracheotomy incisions. Specimens were preserved in formalin and a surgeon and animal technician later conducted
J Am Coll Surg
a mapping and evaluation of each neck specimen. Human tracheal specimens were mapped in situ by one of the investigators. RESULTS In the canine models, 47 necks with 52 attempted cricothyroidotomies were inspected and mapped by the investigators. Four specimens had multiple tracheotomy sites; three had two tracheotomies and one had three tracheotomies. If these multiple attempts are excluded from analysis (the instructor allowed more than one student to practice the procedure in a single animal), 13 of the 43 cricothyroidotomies were misplaced (30.2%). The most common error, in five animals, was insertion between the cricoid cartilage and the first tracheal ring. Four tracheal entry sites were through the hyoid bone, three were above or through the laryngeal ventricle, and one was placed between the first and second tracheal rings. Physician participants in the surgical skills practicum had a higher misplacement rate (12 of 33, 36.4%) than did flight nurses (1 in 10, 10%). This was most likely because the flight nurses, with between 1 and 10 years experience, had bimonthly animal procedure labs, whereas this might have been the physician’s first encounter with an animal model. There were insufficient numbers of physicians in each specialty and training level to draw any valid conclusions regarding subgroups. Cricothyroidotomies performed in human cadavers during the surgical skills practicum were correctly placed in 27 of 28 attempts (96.4%). The only error in placement was a tracheal entry site between the first and second tracheal rings. DISCUSSION Complications of establishing a surgical airway in the emergent setting are fewer when a cricothyroidotomy is performed than when a tracheostomy is performed.3 Some authors contend that the complication rate in the elective setting, even when longterm intubation is required, is lower for cricothyroidotomy, although this is controversial.4 The performance of cricothyroidotomy is uncommon, but may be life-saving. A 32% complication rate in the emergent setting has been reported.5 Incorrect site of tube placement was the most frequent error, with four of five placed through the thyrohyoid membrane. Prolonged procedure times, with potential for anoxia, unsuccessful tube placement, and hemor-
Vol. 195, No. 5, November 2002
rhage were also problematic. Laryngeal fracture with permanent dysphonia occurred in one patient. Accurate and appropriate instruction in cricothyroidotomy technique is critical. Proper surgical technique during the procedure is essential. The first listed objective of the ATLS Cricothyroidotomy Skill Station is to “allow the participant to practice and demonstrate the technique of needle cricothyroidotomy and surgical cricothyroidotomy on a live, anesthetized animal.” But, this procedure relies on the ability to “Identify the surface markings and structures to be noted when performing needle and surgical cricothyroidotomies.”6 External landmarks in the canine model are different than those in the human, and they create errors in the identification of the appropriate surgical site, even with experienced instructors. In this study, canine models were compared with human cadavers as a model for the performance of cricothyroidotomy. Thirteen of 43 (30.2%) cricothyroidotomies were misplaced in dogs. In human cadavers, placement was correct in 27 of 28 (96.4%). Animal models have frequently been used for some aspects of medical training, but differences in the anatomy of these models can create problems for appropriate application of the procedure in humans. Medical professionals learning procedures for the care of human patients must be educated on the anatomic differences of the nonhuman patient. Expert animal technical assistance or preprocedure instructor review of canine anatomy can improve the accuracy of tube placement in the canine model. Lectures and verbal instruction are effective in providing steps for procedure performance, but procedure accuracy, especially in adult learners, can only be taught through the performance of those procedures, either in a real or simulated setting. It is recommended that participants (students and instructors) be made aware of their performance through immediate postprocedure feedback. Evaluation and correction of technique is essential in teaching surgical procedures. Four types of patient models are proposed for use during the ATLS Surgical Skills Practicum: (1) live, anesthetized, nonhuman models (swine, sheep, goat, or canine); (2) human cadavers; (3) anatomic human body mannequins; and (4) nonhuman cadavers.7 The avail-
McCarthy et al
Accuracy of Cricothyroidotomy
629
ability of other models and their accuracy in representing the human body should be similarly evaluated, as in our study, before widespread implementation. In conclusion, cricothyroidotomy in the emergent setting has a lower complication rate than that of tracheostomy. It is essential that this procedure, which is life saving, but only rarely needed, be taught through an accurate method to provide the greatest benefit to patients. In our study, cricothyroidotomy in canine models was appropriately sited only 69.8% of the time; the same procedure performed in human cadavers was accurate 96.4% of the time. Improved teaching techniques can increase accuracy in animal models, but human cadavers represent a far superior model for teaching the procedure accurately on initial instruction. Newer options should be considered and similarly evaluated before widespread implementation. Author contributions
Study conception and design: McCarthy, Castillo Acquisition of data: Ranzinger, Nolan Drafting of manuscript: Ranzinger, Lambert Critical revision: McCarthy Supervision: McCarthy REFERENCES 1. Course Overview: the purpose, history, and concepts of the ATLS Program for doctors. Advanced Trauma Life Support Course for Doctors: Instructor Manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 11. 2. Section II: policies and procedures, chapter 9: policies, procedures, and protocols for the surgical skills practicum. Advanced Trauma Life Support Course for Doctors: Instructor Manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 637–662. 3. Lewis RJ. Tracheostomies: indications, timing, and complications. Clin Chest Med 1992;13:137–149. 4. Brantigan CO, Grow JB. Cricothyroidotomy: elective use in respiratory problems requiring tracheostomy. J Thorac Cardiovasc Surg 1976;71:72–81. 5. McGill J, Clinton JE, Ruiz E. Cricothyrotomy in the emergency department. Ann Emerg Med 1982;11:361–364. 6. Section I: core course content, chapter 2: airway and ventilatory management, Skills Station III: cricothyroidotomy. Advanced Trauma Life Support Course for doctors: instructor manual. Sixth edition. Chicago, IL: American College of Surgeons; 1997: 89–96. 7. Parks S, Hughes I. Alternative models for the ATLS surgical skills practicum. ATLS Announcement. November 7, 2001. American College of Surgeons, Chicago, IL.