American Journal of Emergency Medicine 32 (2014) 1391–1394
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Brief Report
A new strategy for difficult airway management with visual needle cricothyroidotomy: a manikin study☆,☆☆ Yanmei Feng, Ph.D., M.D. a, Huisheng Deng, Ph.D., M.D. b, Xun Liu, M.M. b, Gang Xu, M.M. b, Ziyang Huang, M.M. b, Bingbing Yan, M.M. b, Yijun Liu, M.M. b, Jingjing Lv, M.M. b, Yong Zhang, Ph.D. c, Rui Guo, Ph.D., M.D. d,⁎ a
Department of Respiratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China Department of Geriatrics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China c Department of Ultrasound, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China d Department of Critical Care Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China b
a r t i c l e
i n f o
Article history: Received 28 May 2014 Received in revised form 8 August 2014 Accepted 9 August 2014
a b s t r a c t Background: Conventional needle cricothyroidotomy uses blind manipulation. We investigated the feasibility and efficiency of a new visually guided needle cricothyroidotomy technique. Methods: A 0.9-mm microimaging fiber was delivered into a 14G needle to develop a visual puncture system. 10 inexperienced physicians were randomly assigned to perform 10 repeated needle cricothyroidotomy in each group with both conventional method and visual puncture in a manikin. Tracheal lumen puncture time and number of procedure-related complications were recorded. Results: Under visual guidance, the needle successfully reached the tracheal lumen. The anatomy of the upper and lower airways was acquired by further advancing the microimaging fiber into the tracheal lumen of the visual group. The tracheal lumen puncture time was significantly less in the visual group than in the conventional group (3.85 ± 1.54 vs. 9.84 ± 1.08 seconds, P b .001). Damage to the posterior tracheal wall was not observed in the visual group; however, 21% of manikins in the conventional group had procedure-related complications. Conclusions: Our results demonstrate that visual needle cricothyroidotomy is feasible, and may lead to a decrease in procedure time and procedure-related complications compared to the conventional procedure. In addition, this strategy may also provide useful information for diagnostic purposes; therefore, visual needle cricothyroidotomy may be a new strategy for the management of difficult airways in future care. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Needle cricothyroidotomy is a life-saving strategy that temporarily provides ventilation in the “cannot intubate, cannot ventilate” (CICV) scenario [1]. However, the conventional method is performed blindly, which can make it difficult to confirm needle location in some cases [2]. Furthermore, additional information on the cause of airway obstruction cannot be provided simultaneously. Recently, a 0.9-mm microimaging fiber was used by our research group to develop a visual sputum suction system [3]. In this study, the microimaging fiber was delivered into a 14G needle to guide visual ☆ This study was performed at Chongqing Medical University. ☆☆ Funding support: The present study is supported by the National Natural Science Foundation of China (81201173), the Chongqing Science and Technology Commission (CSTC, 2009ab5218) and Chongqing Municipal Health Bureau project (2009–2317). ⁎ Corresponding author. Department of Critical Care Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China, No. 1 Youyi Road, Yuzhong District, Chongqing 400016, P.R. China. Tel.: +86 139 83207360; fax: +86 023 68811487. E-mail address: [email protected] (R. Guo). http://dx.doi.org/10.1016/j.ajem.2014.08.024 0735-6757/© 2014 Elsevier Inc. All rights reserved.
needle cricothyroidotomy, to investigate the feasibility and efficiency of this video-assisted system. To the best of our knowledge, this is the first study to demonstrate needle cricothyroidotomy with this new system. 2. Materials and methods 2.1. Visual needle cricothyroidotomy system Fig. 1 shows the prototype of the visual needle cricothyroidotomy system. This system was designed to integrate a microimaging fiber (FVS-001MI, Blade Co, Beijing, China) which was previously described in detail [3], into a 14G needle (Smith Medical International Ltd, Hythe, Kent, UK) to facilitate visual guidance during penetration of the cricothyroid membrane. 2.2. Experimental protocol A human analogue model (Zhonghong Teaching Equipment Co Ltd, Shanghai, China) was used, which consisted of a tong, pharynx, vocal cords, bronchus, and tracheobronchial tree. However, the whole
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Fig. 1. A, The prototype of the visually guided needle cricothyroidotomy system, consisting of a monitor, light source port, imaging source port, video capture box, notebook computer, microimaging fiber, and 14G needle. B, At the distal end, there was a microimaging fiber (a), 14G needle (b), “Y” connector (c), and three-way switch (d).
airway system was made with transparent silica gel. To simulate real conditions, the surface was covered with red adhesive tape. In addition, as described previously [3], coagulant simulants comparable to human airway sputum were also randomly injected into the tracheal lumen. After routine draping, the experimental protocols used were as follows: 2.2.1. Protocol 1 The microimaging fiber was delivered, not exceeding the distal end, into a 14 G needle. During the whole procedure of needle cricothyroidotomy, the microimaging fiber was within the needle. Under visual guidance of the microimaging fiber, the needle penetrated the skin, and further advanced into the trachea. Under these conditions, the tracheal lumen puncture time was defined as the time at which the needle touched the skin until the video demonstrated that the needle had successfully reached the tracheal lumen. As alternative choice to determine the cause of dyspnea, the microimaging fiber was delivered beyond the distal end to acquire the structures of the upper and lower airways. Finally, the microimaging fiber was withdrawn from the needle, and the needle remained as a temporary artificial airway. 2.2.2. Protocol 2 Conventional needle cricothyroidotomy followed the standard procedure that was described previously [4]. To detect any potential damage to the posterior tracheal wall, the microimaging fiber was also delivered into a 5-mL syringe (Venous Catheterization kits, Arrow International Inc, Reading, PA) containing 3 mL saline. Then the syringe was connected to a 14G needle for needle cricothyroidotomy. However, unlike the visual group, in the conventional group, the operator was opposite the monitor and blind to the video information; the whole procedure was recorded simultaneously and stored for post-analysis. In this group, the tracheal lumen puncture time was defined as the time when the needle touched the skin until it successfully reached the tracheal lumen, as determined by the free withdrawal of air into the syringe. In this study, 10 physicians enrolled and assigned to perform needle cricothyroidotomy with both conventional method and visual puncture system in a randomized order. In both groups, 10 repeated needle cricothyroidotomies were performed, and procedure-related complications were defined as the needle tip penetrating the posterior tracheal wall. All physicians had less than 1 year of postgraduate
training, and none had previous needle cricothyroidotomy experience. The study was performed according to the guidelines of the regional ethics committee. 2.3. Statistics Data are presented as mean ± SD. SPSS version 10.0 was used for data analysis. Comparisons of tracheal lumen puncture time between the conventional and visual groups used paired t test and the repeated measurement. The procedure-related complications rate between groups was performed using paired χ 2 test. P values less than .05 were considered statistically significant. 3. Results 3.1. Safety study Needle cricothyroidotomy was successfully performed in both groups. In the conventional group, damage to the posterior tracheal wall was observed in 21 cases (21/100, 21%); however, this procedure-related complication was not detected in the visual group (P b .001). 3.2. Visually guided needle cricothyroidotomy Using real-time guidance, the needle progressed and penetrated the cricothyroid membrane, which allowed information about the tracheal structure to be acquired (Fig. 2A). This method allowed the physicians to determine when the needle had successfully advanced into the tracheal lumen. 3.3. Anatomy of airways detected in the visual group The tracheal lumen was properly penetrated under the guidance of the microimaging fiber, and orientating the needle tip towards the upper airway by lowering the puncture angle. Delivering the microimaging fiber beyond the needle tip, then the anatomy of the upper airway, including the pharynx and the vocal cords, was observed (Fig. 2B). Similarly, the lower airway anatomy, including the main bronchus, sputum, carina, left bronchus, and right bronchus, was also acquired (Fig. 2C and D).
Y. Feng et al. / American Journal of Emergency Medicine 32 (2014) 1391–1394
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4. Discussion
Fig. 2. A, The tracheal structure acquired in the visual group, showing the needle tip, posterior tracheal wall (pos.), and bronchus ring. The airway structure was simultaneously acquired by further delivering the microimaging fiber beyond the needle tip. B, The structure of the upper airway, including the pharynx and vocal cord. C, Sputum attached to the tracheal wall. D, The structure of the lower airway, including the carina, left bronchus (L), and right bronchus (R). The whole procedure is easier to interpret in the full motion video clip, which is demonstrated in video 1 in the supplemental data.
3.4. The comparison of tracheal lumen puncture time between the conventional group and the visual group The tracheal lumen puncture times were compared between the groups with paired t-test and repeated measurement. There was learning curve in both groups (Fig. 3). The puncture time was 3.85 ± 1.54 seconds in the visual group, which was significantly less than that in the conventional group (9.84 ± 1.08 seconds, P b .001).
Fig. 3. Comparison of tracheal lumen puncture times between the conventional and visual groups.
The success rate of conventional needle cricothyroidotomy ranged from 30% to 95% [1], partially due to blind manipulation. In addition, the needle tip within tracheal lumen was hard to confirm in some cases. Under these conditions, further advancing the needle may increase the incidence of perforation of the posterior tracheal wall and cause serious complications. In this study, the incidence of procedurerelated complication was 21% in the conventional group. A study using a human cadaver airway model reported a similar incidence of 26.7% of posterior tracheal wall injury and posterior tracheal wall perforation [1]. In this study, damage to the posterior tracheal wall was not observed in the visual group, which indicates that accurate needle tip confirmation may help to reduce procedure-related complications. This improvement is important. Since CICV is a rare emergency, insufficient experience with this in practice may also contribute to the risk of posterior tracheal wall injury [1]. To the best of our knowledge, this study is the first to incorporate a microimaging fiber into a 14G needle to provide visual guidance during needle cricothyroidotomy. Therefore, this strategy may also help to compensate for a practitioner’s insufficient experience with CICV and/or replace the subjective feeling of conventional method, both of which can lead to procedure-related complications. Further evaluations of efficiency between experienced skilled and less experienced beginners may be more relevant to investigate this hypothesis in animal model or clinic trial. Although the bronchofiberscope was developed to assist with needle tip location during needle cricothyroidotomy [5], in some cases, such as severe upper airway obstruction, the bronchofiberscope is unable to advance into the tracheal lumen, making it difficult to confirm needle location. In addition, this procedure can also cause secondary discomfort to patients and may induce additional procedure-related complications. However, as the microimaging fiber used in the present study is small in diameter, it can be delivered into a 14G needle and provide the anatomical structure of the tracheal lumen (Fig. 2A), assist with needle tip location, minimize secondary harm to the patient, and be independent of the structure of the upper airway structure. Therefore, visually guided needle cricothyroidotomy may provide a new way to monitor needle tip location in the future. A previous study demonstrated that a human analogue model cannot reliably simulate the real conditions of clinic practice, especially for patients without full sedation and analgesia [6]. Agitation or bronchospasm may make it difficult to judge needle location when using conventional needle cricothyroidotomy. Visually guided needle cricothyroidotomy may be more valuable under such conditions. Time is an important consideration when dealing with needle cricothyroidotomy. In a cadaver study, Schaumann et al [7] showed that the first ventilation with a breathing bag during needle cricothyroidotomy took 108.6 seconds, which was 28 seconds shorter than ventilation using a surgical approach. Subsequently, other studies reported variable procedure times, ranging from 33 to 82 seconds [1,8,9]. However, a head-to-head comparison among different studies is often meaningless, due to differences in factors such as the definition of successful procedure time, protocol, airway model (eg, manikin, animal, cadaver, patient), and individual experiences. In the present study, under similar conditions, less time was needed to perform needle cricothyroidotomy in the visual group than in the conventional group, possibly because the needle location could be confirmed simultaneously. Using real-time guidance, successful needle cricothyroidotomy was determined immediately once the needle tip reached the tracheal lumen; however, the conventional procedure needed aspiration of air into the syringe to confirm needle location, which prolongs the time needed to assure the success of this technique. Therefore, visually guided needle cricothyroidotomy may help simplify the entire procedure and also reduce procedure time.
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Compared to conventional needle cricothyroidotomy, this new strategy can simultaneously provide additional information on the anatomy of the upper and lower airways (Fig. 2B and D), which is helpful for quickly determining the cause of airway obstruction. To the best of our knowledge, this is the first study to show how needle cricothyroidotomy can be used to simultaneously acquire information on airway structures. This is important. To date, the indication of needle cricothyroidotomy has only been suitable for releasing dyspnea due to upper airway obstruction; however, in some cases, both upper and lower airway obstructions exist simultaneously or sequentially. If not identified in time, and if the needle is continuously used as an artificial airway, or following jet ventilation, this condition may worsen the outcome of an already critically ill patient [10]. Thus, this new strategy could partly compensate for this shortcoming, and may provide valuable information for guiding proper airway management in the future. 5. Study limitations This study used a manikin to investigate the feasibility and efficiency of needle cricothyroidotomy using a visually guided puncture system. Future evaluations should use real patients, especially for the evaluation of efficiency and safety. In addition, further experience should be accumulated with more participants and repeated procedures to investigate this new system. 6. Conclusions Visually guided needle cricothyroidotomy was feasible in manikins and led to a decrease in procedure time and procedure-related complications. Moreover, the anatomy of both the upper and lower airways was acquired, which could provide useful information for diagnostic purposes. Therefore, visually guided needle cricothyroi-
dotomy may be a new strategy for difficult airway management in future care.
Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.ajem.2014.08.024.
References [1] Helm M, Hossfeld B, Jost C, Lampl L, Bockers T. Emergency cricothyroidotomy performed by inexperienced clinicians–surgical technique versus indicator-guided puncture technique. Emerg Med J 2013;30:646–9. [2] Engelhardt T, Weiss M. A child with a difficult airway: what do I do next? Curr Opin Anaesthesiol 2012;25:326–32. [3] Lv J, Wu J, Guo R, Liu X, Yan B, Deng H. Laboratory test of a visual sputum suctioning system. Respir Care 2013;58:1637–42. [4] Schuh JR, Bettendorf R, Shapiro D, Trowbridge DL, Lujan E, Boyle P, et al. Confirmation of needle cricothyroidotomy using an esophageal detector device in a porcine model. Mil Med 2010;175:686–7. [5] Murad I, Abib SC, Lima DP, Ferreira PS, dos Santos EQ, Bataglia TV. The influence of hemorrhagic shock on ventilation through needle cricothyroidotomy in pigs. Am J Emerg Med 2012;30:1684–90. [6] Timmermann A. Supraglottic airways in difficult airway management: successes, failures, use and misuse. Anaesthesia 2011;66(Suppl. 2):45–56. [7] Schaumann N, Lorenz V, Schellongowski P, Staudinger T, Locker GJ, Burgmann H, et al. Evaluation of Seldinger technique emergency cricothyroidotomy versus standard surgical cricothyroidotomy in 200 cadavers. Anesthesiology 2005;102: 7–11. [8] Dinsmore J, Heard AM, Green RJ. The use of ultrasound to guide time-critical cannula tracheotomy when anterior neck airway anatomy is unidentifiable. Eur J Anaesthesiol 2011;28:506–10. [9] Mariappa V, Stachowski E, Balik M, Clark P, Nayyar V. Cricothyroidotomy: comparison of three different techniques on a porcine airway. Anaesth Intensive Care 2009;37:961–7. [10] Hamaekers AE, Borg PA, Enk D. A bench study of ventilation via two selfassembled jet devices and the Oxygen Flow Modulator in simulated upper airway obstruction. Anaesthesia 2009;64:1353–8.
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Brief Report
A new strategy for difficult airway management with visual needle cricothyroidotomy: a manikin study☆,☆☆ Yanmei Feng, Ph.D., M.D. a, Huisheng Deng, Ph.D., M.D. b, Xun Liu, M.M. b, Gang Xu, M.M. b, Ziyang Huang, M.M. b, Bingbing Yan, M.M. b, Yijun Liu, M.M. b, Jingjing Lv, M.M. b, Yong Zhang, Ph.D. c, Rui Guo, Ph.D., M.D. d,⁎ a
Department of Respiratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China Department of Geriatrics, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China c Department of Ultrasound, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China d Department of Critical Care Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China b
a r t i c l e
i n f o
Article history: Received 28 May 2014 Received in revised form 8 August 2014 Accepted 9 August 2014
a b s t r a c t Background: Conventional needle cricothyroidotomy uses blind manipulation. We investigated the feasibility and efficiency of a new visually guided needle cricothyroidotomy technique. Methods: A 0.9-mm microimaging fiber was delivered into a 14G needle to develop a visual puncture system. 10 inexperienced physicians were randomly assigned to perform 10 repeated needle cricothyroidotomy in each group with both conventional method and visual puncture in a manikin. Tracheal lumen puncture time and number of procedure-related complications were recorded. Results: Under visual guidance, the needle successfully reached the tracheal lumen. The anatomy of the upper and lower airways was acquired by further advancing the microimaging fiber into the tracheal lumen of the visual group. The tracheal lumen puncture time was significantly less in the visual group than in the conventional group (3.85 ± 1.54 vs. 9.84 ± 1.08 seconds, P b .001). Damage to the posterior tracheal wall was not observed in the visual group; however, 21% of manikins in the conventional group had procedure-related complications. Conclusions: Our results demonstrate that visual needle cricothyroidotomy is feasible, and may lead to a decrease in procedure time and procedure-related complications compared to the conventional procedure. In addition, this strategy may also provide useful information for diagnostic purposes; therefore, visual needle cricothyroidotomy may be a new strategy for the management of difficult airways in future care. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Needle cricothyroidotomy is a life-saving strategy that temporarily provides ventilation in the “cannot intubate, cannot ventilate” (CICV) scenario [1]. However, the conventional method is performed blindly, which can make it difficult to confirm needle location in some cases [2]. Furthermore, additional information on the cause of airway obstruction cannot be provided simultaneously. Recently, a 0.9-mm microimaging fiber was used by our research group to develop a visual sputum suction system [3]. In this study, the microimaging fiber was delivered into a 14G needle to guide visual ☆ This study was performed at Chongqing Medical University. ☆☆ Funding support: The present study is supported by the National Natural Science Foundation of China (81201173), the Chongqing Science and Technology Commission (CSTC, 2009ab5218) and Chongqing Municipal Health Bureau project (2009–2317). ⁎ Corresponding author. Department of Critical Care Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China, No. 1 Youyi Road, Yuzhong District, Chongqing 400016, P.R. China. Tel.: +86 139 83207360; fax: +86 023 68811487. E-mail address: [email protected] (R. Guo). http://dx.doi.org/10.1016/j.ajem.2014.08.024 0735-6757/© 2014 Elsevier Inc. All rights reserved.
needle cricothyroidotomy, to investigate the feasibility and efficiency of this video-assisted system. To the best of our knowledge, this is the first study to demonstrate needle cricothyroidotomy with this new system. 2. Materials and methods 2.1. Visual needle cricothyroidotomy system Fig. 1 shows the prototype of the visual needle cricothyroidotomy system. This system was designed to integrate a microimaging fiber (FVS-001MI, Blade Co, Beijing, China) which was previously described in detail [3], into a 14G needle (Smith Medical International Ltd, Hythe, Kent, UK) to facilitate visual guidance during penetration of the cricothyroid membrane. 2.2. Experimental protocol A human analogue model (Zhonghong Teaching Equipment Co Ltd, Shanghai, China) was used, which consisted of a tong, pharynx, vocal cords, bronchus, and tracheobronchial tree. However, the whole
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Fig. 1. A, The prototype of the visually guided needle cricothyroidotomy system, consisting of a monitor, light source port, imaging source port, video capture box, notebook computer, microimaging fiber, and 14G needle. B, At the distal end, there was a microimaging fiber (a), 14G needle (b), “Y” connector (c), and three-way switch (d).
airway system was made with transparent silica gel. To simulate real conditions, the surface was covered with red adhesive tape. In addition, as described previously [3], coagulant simulants comparable to human airway sputum were also randomly injected into the tracheal lumen. After routine draping, the experimental protocols used were as follows: 2.2.1. Protocol 1 The microimaging fiber was delivered, not exceeding the distal end, into a 14 G needle. During the whole procedure of needle cricothyroidotomy, the microimaging fiber was within the needle. Under visual guidance of the microimaging fiber, the needle penetrated the skin, and further advanced into the trachea. Under these conditions, the tracheal lumen puncture time was defined as the time at which the needle touched the skin until the video demonstrated that the needle had successfully reached the tracheal lumen. As alternative choice to determine the cause of dyspnea, the microimaging fiber was delivered beyond the distal end to acquire the structures of the upper and lower airways. Finally, the microimaging fiber was withdrawn from the needle, and the needle remained as a temporary artificial airway. 2.2.2. Protocol 2 Conventional needle cricothyroidotomy followed the standard procedure that was described previously [4]. To detect any potential damage to the posterior tracheal wall, the microimaging fiber was also delivered into a 5-mL syringe (Venous Catheterization kits, Arrow International Inc, Reading, PA) containing 3 mL saline. Then the syringe was connected to a 14G needle for needle cricothyroidotomy. However, unlike the visual group, in the conventional group, the operator was opposite the monitor and blind to the video information; the whole procedure was recorded simultaneously and stored for post-analysis. In this group, the tracheal lumen puncture time was defined as the time when the needle touched the skin until it successfully reached the tracheal lumen, as determined by the free withdrawal of air into the syringe. In this study, 10 physicians enrolled and assigned to perform needle cricothyroidotomy with both conventional method and visual puncture system in a randomized order. In both groups, 10 repeated needle cricothyroidotomies were performed, and procedure-related complications were defined as the needle tip penetrating the posterior tracheal wall. All physicians had less than 1 year of postgraduate
training, and none had previous needle cricothyroidotomy experience. The study was performed according to the guidelines of the regional ethics committee. 2.3. Statistics Data are presented as mean ± SD. SPSS version 10.0 was used for data analysis. Comparisons of tracheal lumen puncture time between the conventional and visual groups used paired t test and the repeated measurement. The procedure-related complications rate between groups was performed using paired χ 2 test. P values less than .05 were considered statistically significant. 3. Results 3.1. Safety study Needle cricothyroidotomy was successfully performed in both groups. In the conventional group, damage to the posterior tracheal wall was observed in 21 cases (21/100, 21%); however, this procedure-related complication was not detected in the visual group (P b .001). 3.2. Visually guided needle cricothyroidotomy Using real-time guidance, the needle progressed and penetrated the cricothyroid membrane, which allowed information about the tracheal structure to be acquired (Fig. 2A). This method allowed the physicians to determine when the needle had successfully advanced into the tracheal lumen. 3.3. Anatomy of airways detected in the visual group The tracheal lumen was properly penetrated under the guidance of the microimaging fiber, and orientating the needle tip towards the upper airway by lowering the puncture angle. Delivering the microimaging fiber beyond the needle tip, then the anatomy of the upper airway, including the pharynx and the vocal cords, was observed (Fig. 2B). Similarly, the lower airway anatomy, including the main bronchus, sputum, carina, left bronchus, and right bronchus, was also acquired (Fig. 2C and D).
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4. Discussion
Fig. 2. A, The tracheal structure acquired in the visual group, showing the needle tip, posterior tracheal wall (pos.), and bronchus ring. The airway structure was simultaneously acquired by further delivering the microimaging fiber beyond the needle tip. B, The structure of the upper airway, including the pharynx and vocal cord. C, Sputum attached to the tracheal wall. D, The structure of the lower airway, including the carina, left bronchus (L), and right bronchus (R). The whole procedure is easier to interpret in the full motion video clip, which is demonstrated in video 1 in the supplemental data.
3.4. The comparison of tracheal lumen puncture time between the conventional group and the visual group The tracheal lumen puncture times were compared between the groups with paired t-test and repeated measurement. There was learning curve in both groups (Fig. 3). The puncture time was 3.85 ± 1.54 seconds in the visual group, which was significantly less than that in the conventional group (9.84 ± 1.08 seconds, P b .001).
Fig. 3. Comparison of tracheal lumen puncture times between the conventional and visual groups.
The success rate of conventional needle cricothyroidotomy ranged from 30% to 95% [1], partially due to blind manipulation. In addition, the needle tip within tracheal lumen was hard to confirm in some cases. Under these conditions, further advancing the needle may increase the incidence of perforation of the posterior tracheal wall and cause serious complications. In this study, the incidence of procedurerelated complication was 21% in the conventional group. A study using a human cadaver airway model reported a similar incidence of 26.7% of posterior tracheal wall injury and posterior tracheal wall perforation [1]. In this study, damage to the posterior tracheal wall was not observed in the visual group, which indicates that accurate needle tip confirmation may help to reduce procedure-related complications. This improvement is important. Since CICV is a rare emergency, insufficient experience with this in practice may also contribute to the risk of posterior tracheal wall injury [1]. To the best of our knowledge, this study is the first to incorporate a microimaging fiber into a 14G needle to provide visual guidance during needle cricothyroidotomy. Therefore, this strategy may also help to compensate for a practitioner’s insufficient experience with CICV and/or replace the subjective feeling of conventional method, both of which can lead to procedure-related complications. Further evaluations of efficiency between experienced skilled and less experienced beginners may be more relevant to investigate this hypothesis in animal model or clinic trial. Although the bronchofiberscope was developed to assist with needle tip location during needle cricothyroidotomy [5], in some cases, such as severe upper airway obstruction, the bronchofiberscope is unable to advance into the tracheal lumen, making it difficult to confirm needle location. In addition, this procedure can also cause secondary discomfort to patients and may induce additional procedure-related complications. However, as the microimaging fiber used in the present study is small in diameter, it can be delivered into a 14G needle and provide the anatomical structure of the tracheal lumen (Fig. 2A), assist with needle tip location, minimize secondary harm to the patient, and be independent of the structure of the upper airway structure. Therefore, visually guided needle cricothyroidotomy may provide a new way to monitor needle tip location in the future. A previous study demonstrated that a human analogue model cannot reliably simulate the real conditions of clinic practice, especially for patients without full sedation and analgesia [6]. Agitation or bronchospasm may make it difficult to judge needle location when using conventional needle cricothyroidotomy. Visually guided needle cricothyroidotomy may be more valuable under such conditions. Time is an important consideration when dealing with needle cricothyroidotomy. In a cadaver study, Schaumann et al [7] showed that the first ventilation with a breathing bag during needle cricothyroidotomy took 108.6 seconds, which was 28 seconds shorter than ventilation using a surgical approach. Subsequently, other studies reported variable procedure times, ranging from 33 to 82 seconds [1,8,9]. However, a head-to-head comparison among different studies is often meaningless, due to differences in factors such as the definition of successful procedure time, protocol, airway model (eg, manikin, animal, cadaver, patient), and individual experiences. In the present study, under similar conditions, less time was needed to perform needle cricothyroidotomy in the visual group than in the conventional group, possibly because the needle location could be confirmed simultaneously. Using real-time guidance, successful needle cricothyroidotomy was determined immediately once the needle tip reached the tracheal lumen; however, the conventional procedure needed aspiration of air into the syringe to confirm needle location, which prolongs the time needed to assure the success of this technique. Therefore, visually guided needle cricothyroidotomy may help simplify the entire procedure and also reduce procedure time.
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Compared to conventional needle cricothyroidotomy, this new strategy can simultaneously provide additional information on the anatomy of the upper and lower airways (Fig. 2B and D), which is helpful for quickly determining the cause of airway obstruction. To the best of our knowledge, this is the first study to show how needle cricothyroidotomy can be used to simultaneously acquire information on airway structures. This is important. To date, the indication of needle cricothyroidotomy has only been suitable for releasing dyspnea due to upper airway obstruction; however, in some cases, both upper and lower airway obstructions exist simultaneously or sequentially. If not identified in time, and if the needle is continuously used as an artificial airway, or following jet ventilation, this condition may worsen the outcome of an already critically ill patient [10]. Thus, this new strategy could partly compensate for this shortcoming, and may provide valuable information for guiding proper airway management in the future. 5. Study limitations This study used a manikin to investigate the feasibility and efficiency of needle cricothyroidotomy using a visually guided puncture system. Future evaluations should use real patients, especially for the evaluation of efficiency and safety. In addition, further experience should be accumulated with more participants and repeated procedures to investigate this new system. 6. Conclusions Visually guided needle cricothyroidotomy was feasible in manikins and led to a decrease in procedure time and procedure-related complications. Moreover, the anatomy of both the upper and lower airways was acquired, which could provide useful information for diagnostic purposes. Therefore, visually guided needle cricothyroi-
dotomy may be a new strategy for difficult airway management in future care.
Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.ajem.2014.08.024.
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