American Journal of Emergency Medicine 32 (2014) 267–269
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Brief Report
The effect of sonologist experience on the ability to determine endotracheal tube location using transtracheal ultrasound☆,☆☆,★ Robert Stuntz, MD, RDMS ⁎, Erik Kochert, MD, Thompson Kehrl, MD, RDMS, Walter Schrading, MD Department of Emergency Medicine, Wellspan York Hospital, York, PA, USA
a r t i c l e
i n f o
Article history: Received 20 August 2013 Received in revised form 6 November 2013 Accepted 16 November 2013
a b s t r a c t Study objective: Transtracheal ultrasound has been described as a method to evaluate endotracheal tube placement. Correlation between sonologist experience and the successful use of transtracheal ultrasound to identify endotracheal tube location has not been examined. Our objectives were to evaluate emergency physicians' ability to correctly identify endotracheal tube location using transtracheal ultrasound and to evaluate the role operator experience plays in successful identification of tube placement. Methods: This was a cross-sectional, single-blinded study conducted in a cadaver laboratory. Two cadavers were used as models. One cadaver had an endotracheal tube placed in the esophagus, and the second had the tube placed in the trachea. Participants were asked to evaluate tube placement using transtracheal ultrasound and to record their interpretation. Examination clips were reviewed by the emergency ultrasound fellowship director. Descriptive statistics and χ2 test were used for analysis. Results: Twenty-nine participants were included, 8 (27.6%) of whom were considered to be “most experienced” based on previous ultrasound experience (N 150 scans). Eleven of 29 correctly identified esophageal intubation and 18 of 29 correctly identified tracheal intubation, resulting in a sensitivity of 62.0% (95% confidence interval [CI], 42.3-79.3) and a specificity of 37.9% (95% CI, 20.7-57.7). Transtracheal ultrasound performed by the most experienced sonologists showed better sensitivity and specificity, 75.0% (95% CI, 34.9-96.8) and 62.5% (95% CI, 24.5-91.5), respectively. Conclusion: Most participants obtained adequate images, but correct interpretation of the images was poor. The most experienced sonologists correctly identified tube location more often. Additional education would be required before adopting this method. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The use of ultrasound (US) in the point-of-care setting is rapidly expanding, especially in the fields of emergency medicine (EM) and critical care. Airway management requires rapid confirmation of endotracheal (ET) tube placement, and misplacement can have significant consequences. Several methods for confirmation of tube placement are available, including direct visualization of the vocal cords, chest radiography, auscultation, and end-tidal capnography. End-tidal capnography has been shown to be the most reliable method
☆ No grants or other financial support have been provided. ☆☆ None of the authors have any conflicts of interest to disclose. ★ R.S., E.K., T.K., and W.S. conceived and designed the study. R.S. authored the institutional review board submission, and E.K., T.K., and W.S. provided editorial support. R.S. prepared all study material. R.S., E.K., and W.S. participated in the cadaver laboratory and data acquisition. R.S. managed the data, including quality control. T.K. performed tape review and data collection based on that review. E.K. provided statistical advice and assisted with data analysis. R.S. drafted the manuscript, and all authors contributed substantially to its revision. ⁎ Corresponding author. Department of Emergency Medicine, Wellspan York Hospital, York, PA 17405. E-mail address: [email protected] (R. Stuntz). 0735-6757/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2013.11.032
for determining tube placement; however, its expense may limit availability in some locations. Previous studies have examined the use of transtracheal US (TTUS) to help identify ET tube location [1-4]. Chou et al [5] described a novel protocol, the Tracheal Rapid Ultrasound Exam (TRUE), which used TTUS to confirm ET tube placement as an alternative to end-tidal capnography. The described protocol uses an ultrasonography US probe over the suprasternal trachea in the transverse plane to evaluate for the presence of a hyperechoic airmucosa interface with posterior comet tail reverberation artifact. The presence of one air-mucosa interface with posterior comet tail indicates tracheal intubation, whereas the presence of 2 such interfaces indicates esophageal intubation. In the study performed by Chou et al, this protocol was performed by 2 senior EM residents who had completed all requisite training for US required by their residency. In addition, they received specific training in TTUS, which consisted of a 1-hour didactic session and 8 hours of hands-on training. They were also supervised by an emergency physician with 10 years of emergency US experience who was certified by the Society of Ultrasound in Medicine, Republic of China, Taiwan. In experienced hands, TRUE was shown to be sensitive and specific with short examination times. Other studies investigating the use of US for identification of ET tube location have been
268
R. Stuntz et al. / American Journal of Emergency Medicine 32 (2014) 267–269
performed with experienced sonologists [4,6]. Ultrasound is known to be operator dependent. To our knowledge, no study to date has investigated the role of sonographer experience in correct identification of ET tube placement. The goals of this study are to determine the ability of emergency physicians to successfully identify ET tube location using TTUS and to evaluate the role sonologist experience plays in successful identification of tube placement.
Ultrasound experience
Reported %
0-50 scans 14 51-100 scans 6 101-150 scans 1 N150 scans 8 Total 29
48.3 20.7 3.4 27.6 100
Number–educational level 4-MS4, 6-R1, 3-R2, 1-attending 4-R2, 2-R3 1-R2 1-R1, 1-R2, 1-R3, 1-fellow, 4-attending 4-MS4, 7-R1, 9-R2, 3-R3, 1-fellow, 5-attending
MS4, fourth-year medical student; R1/R2/R3, first/second/third-year EM resident; fellow, emergency US fellow; attending, EM attending.
2. Materials and methods This was a cross-sectional, single-blinded study conducted during a procedural cadaver laboratory. The study was approved by the institutional review board. Participants included EM residents, medical students, and attending physicians. Prior to participation, the study was explained, and participation was made voluntary. One week prior to the study, all participants were given an illustrated instructional handout describing the proper technique for TTUS to identify both tracheal and esophageal intubations. The handout included illustrations taken from the TRUE study showing US-generated images of tracheal and esophageal tube placement. Written instructions were also provided on techniques to obtain adequate images and to correctly interpret the generated images. These instructions were provided to all participants a second time for additional review on the day of the study. Each study participant was de-identified and assigned a study number. Participants were asked to fill out a brief survey describing their level of training, level of US experience, and time spent reviewing the instructional material. The American College of Emergency Physicians recommends a minimum of 150 scans in addition to didactic time dedicated to US education to be deemed competent in emergency US [7]. Therefore, we defined experienced sonologists as those who self-reported performing greater than 150 scans and inexperienced sonologists as those who self-reported performing less than 150 scans. Two cadavers with similar neck and airway anatomy were used as models. One cadaver had an ET tube placed in the esophagus, whereas the second had an ET tube placed in the trachea. They were intubated under direct laryngoscopy by an experienced emergency physician who did not otherwise participate in the study using size 7.5 ET tubes with 10 cc of air inflated into the cuffs. Participants were blinded to the location of the tube, and informed tube placement could be the same or different in both cadavers. Subjects were asked to determine tube placement using TTUS with a high-resolution 13-6 MHz linear transducer (SonoSite M Turbo, Bothell, WA) following the TRUE protocol. Subjects were randomized to start on cadaver A or B and performed their examinations sequentially. They were not allowed to discuss results with other participants. Subjects were not allowed to manipulate the tube in any way. Image interpretation was recorded for all participants. Factors affecting image quality, including gain and depth, were manipulated at the discretion of the participants. Video clips of the examinations were recorded for later review. A brief post– participation survey was completed by each participant to assess the comfort level and confidence regarding accuracy of image acquisition
Table 1 Breakdown of study participants
MS4 R1 R2 R3 Ultrasound fellow EM attending Total
Table 2 Self-reported number of scans performed by study participants
No.
%
4 7 9 3 1 5 29
13.8 24.1 31.0 10.3 3.4 17.2 100
MS4, fourth-year medical student; R1/R2/R3, first/second/third-year EM resident.
and interpretation. Video clips were examined at a later time by the emergency US fellowship director for image quality, time spent on the examination, and accuracy of interpretation of tube location. Prestudy and poststudy surveys were completed for each participant. Data collected from the US director image review included technical adequacy of the study, interpretation of tube location based on images provided for each subject and cadaver, and total examination time for each subject and cadaver. All investigators were subsequently unblinded to correct tube location for the purpose of statistical analysis. Descriptive statistics and χ 2 test were used to analyze the data.
3. Results In total, 29 subjects performed TTUS on 2 cadavers, for a total of 58 scans. All eligible participants chose to participate in the study. Table 1 depicts the levels of training for the study participants. Of the 29 participants, 8 (27.6%) were considered experienced sonologists (Table 2). Only 1 participant (the US fellow) had performed TTUS for evaluation of ET tube location prior to this study. All participants reviewed the educational material, with 62.1% having reviewed the images and protocol within the hour prior to the study. Cadavers were identified as A and B. The ET tubes were placed in the esophagus of cadaver A, and the trachea of cadaver B. Eleven (37.9%) of 29 subjects correctly identified esophageal tube location in cadaver A, and 18 (62.1%) of 29 subjects correctly identified tracheal tube location in cadaver B. These results produce a sensitivity of 62.0% (95% confidence interval [CI], 42.3-79.3) and a specificity of 37.9% (95% CI, 20.7-57.7) for the ability of TTUS to predict the correct placement of an ET tube in a cadaver model. Mean time spent interpreting images for cadavers A and B were 24.73 and 24.89 seconds, respectively (Table 3). Subgroup analysis revealed that 6 of the 8 subjects deemed “experienced sonologists” correctly identified tracheal intubation, and 5 of the 8 correctly identified esophageal intubation. This resulted in better test sensitivity and specificity among the most experienced sonologists, 75.0% (95% CI, 34.9-96.8) and 62.5% (95% CI, 24.5-91.5), respectively. Owing to problems with recording, clips for 3 of the participants were not reviewed and thus excluded from data analysis. Video of the remaining 26 subjects was reviewed, and all but 1 participant obtained images deemed adequate for analysis. Of the recorded images available for review, 96.2% were adequate for interpretation.
Table 3 Time spent scanning each cadaver recorded on clip review by ultrasound fellowship director
Cadaver A Cadaver B
Mean (s)
Minimum (s)
Maximum (s)
Range (s)
SD (s)
24.73 24.89
6 10
76 103
70 93
18.08 20.63
R. Stuntz et al. / American Journal of Emergency Medicine 32 (2014) 267–269
3.1. Limitations This was a small, single-center study, with only 29 participants. In addition, the images from 3 subjects were not available for later review. This study was performed on only 2 cadavers in a single cadaver laboratory, and thus, the results may not be generalizable to the general emergency department population. Neck and airway anatomy were chosen to be similar, so there should not have been limitations on ability to acquire adequate images, and participants did not know the location or pattern of tube placement in the cadavers. Our educational intervention was limited to still images and written instructions, no more than one would obtain by reading the TRUE study. This limitation of education was by design, as we wanted to determine the ability of providers with varying degrees of US experience to use this examination based on the published protocol. We are limited by the fact that US experience level was self-reported.
269
tool, sensitivity and specificity were greatly improved, 97.1% and 100%, respectively [10]. This has been suggested in recently published research, as well [8]. The use of adjuncts to assist in proper identification of ET tube location has also been investigated. Goksu et al [11] looked into the effect of using a stylet to aid in US confirmation of intubation. Stylet use did not result in more accurate identification. Uya et al [12] showed that ET tubes with saline-filled cuffs allowed for successful identification of ET tube location in 39 of 40 cases, with a sensitivity of 96% for identifying tracheal location. Further study is needed to see if similar adjuncts, in combination with dedicated training, would allow for improved sensitivity for this technique. In summary, although most participants were able to obtain adequate images, correct interpretation of the images was poor. More experienced sonologists were more often able to correctly identify tube location. More in-depth education and perhaps proficiency testing should be required before adopting this US modality.
4. Discussion Ultrasound has been previously studied in the confirmation of ET intubation, with recent studies suggesting a TTUS protocol as a promising alternative for confirmation of ET tube placement [5]. This protocol was used with success in a subsequent study by the same authors in real-time intubations of patients undergoing cardiopulmonary resuscitation with similar success [8]. Ultrasound is a tool that can be used by most physicians with minimal training; however, US is known to be operator dependent. A recently published study concluded that airway US for ET tube placement could replace endtidal capnography for ET tube confirmation [9]. Our goals were to determine the ability of emergency physicians to successfully identify ET tube position using TTUS and to evaluate the role operator experience plays in successful identification of tube placement. Most participants in our study obtained adequate images, with 96.2% of obtained images being deemed adequate for interpretation. However, correct interpretation of the images was poor, especially in light of other published data [5,8,9]. Experienced sonologists were able to correctly identify tube location more often; however, even in this subgroup, the sensitivity and specificity fell short of previously reported values, and overlapping CIs do not allow for significance. The consequences of misidentifying ET tube placement can be catastrophic. As US becomes more available, it is important to recognize its limitations in the hands of inexperienced providers. As this study illustrates, even in the hands of experienced sonologists who are comfortable with performing US, new techniques do not fare well without proper education. In one previous study, EM residents were instructed on typical normal tracheal findings on TTUS, as well as findings associated with tracheal intubation. They then evaluated resident ability to identify tube location in cadavers using both static and dynamic methods. They found poor sensitivity (51%) in static identification; however, when used in real time during placement of the ET tube as a dynamic
Acknowledgment We would like to thank Theodore Bell, Barbie Stahlman, and Catherine Kelly for their assistance with data collection, statistical analysis, and manuscript preparation. References [1] Drescher MJ, Conrad FU, Schamban NE. Identification and description of esophageal intubation using ultrasound. Acad Emerg Med 2000;7:722–5. [2] Milling TJ, Jones M, Khan T, et al. Transtracheal 2-D ultrasound for identification of esophageal intubation. J Emerg Med 2007;32(4):409–14. [3] Muslu B, Sert H, Kaya A, et al. Use of sonography for rapid identification of esophageal and tracheal intubations in adult patients. J Ultrasound Med 2011;30(5):671–6. [4] Werner SL, Smith CE, Goldstein JR, et al. Pilot study to evaluate the accuracy of ultrasonography in confirming endotracheal tube placement. Ann Emerg Med 2007;49(1):75–80. [5] Chou HC, et al. Tracheal rapid ultrasound exam (T.R.U.E.) for confirming endotracheal tube placement during emergency intubation. Resuscitation 2011;82(10):1279–84. [6] Galiciano J, Bush AJ, Godambe SA. Use of bedside ultrasonography for endotracheal tube placement in pediatric patients: a feasibility study. Pediatrics 2007;120:1297–303. [7] American College of Emergency Physicians. Policy Statement: Emergency Ultrasound Guidelines. October 2008. [8] Chou HC, et al. Real-time tracheal ultrasonography for confirmation of endotracheal tube pleacement during cardiopulmonary resuscitation. Resuscitation 2013;84(12):1708–12. [9] Osman AB, Chuan TW, Manikam R. A feasibility study on bedside upper airway ultrasonography compared to waveform capnography for verifying endotracheal tube location after intubation. Crit Ultrasound J 2013;5(1):7. [10] Ma G, Davis DP, Schmitt J, et al. The sensitivity and specificity of transcricothyroid ultrasonography to confirm endotracheal tube placement in a cadaver model. J Emerg Med 2007;32(4):405–7. [11] Goksu E, Sayrac V, Oktay C, et al. How stylet use can effect confirmation of endotracheal tube position using ultrasound. Am J Emerg Med 2010;28:32–6. [12] Uya A, Spear D, Patel K, Okada P, Sheeran P, McCreight A. Can novice sonographers accurately locate an endotracheal tube with a saline-filled cuff in a cadaver model? A pilot study. Acad Emerg Med 2012;19(3):361–4.
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Brief Report
The effect of sonologist experience on the ability to determine endotracheal tube location using transtracheal ultrasound☆,☆☆,★ Robert Stuntz, MD, RDMS ⁎, Erik Kochert, MD, Thompson Kehrl, MD, RDMS, Walter Schrading, MD Department of Emergency Medicine, Wellspan York Hospital, York, PA, USA
a r t i c l e
i n f o
Article history: Received 20 August 2013 Received in revised form 6 November 2013 Accepted 16 November 2013
a b s t r a c t Study objective: Transtracheal ultrasound has been described as a method to evaluate endotracheal tube placement. Correlation between sonologist experience and the successful use of transtracheal ultrasound to identify endotracheal tube location has not been examined. Our objectives were to evaluate emergency physicians' ability to correctly identify endotracheal tube location using transtracheal ultrasound and to evaluate the role operator experience plays in successful identification of tube placement. Methods: This was a cross-sectional, single-blinded study conducted in a cadaver laboratory. Two cadavers were used as models. One cadaver had an endotracheal tube placed in the esophagus, and the second had the tube placed in the trachea. Participants were asked to evaluate tube placement using transtracheal ultrasound and to record their interpretation. Examination clips were reviewed by the emergency ultrasound fellowship director. Descriptive statistics and χ2 test were used for analysis. Results: Twenty-nine participants were included, 8 (27.6%) of whom were considered to be “most experienced” based on previous ultrasound experience (N 150 scans). Eleven of 29 correctly identified esophageal intubation and 18 of 29 correctly identified tracheal intubation, resulting in a sensitivity of 62.0% (95% confidence interval [CI], 42.3-79.3) and a specificity of 37.9% (95% CI, 20.7-57.7). Transtracheal ultrasound performed by the most experienced sonologists showed better sensitivity and specificity, 75.0% (95% CI, 34.9-96.8) and 62.5% (95% CI, 24.5-91.5), respectively. Conclusion: Most participants obtained adequate images, but correct interpretation of the images was poor. The most experienced sonologists correctly identified tube location more often. Additional education would be required before adopting this method. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The use of ultrasound (US) in the point-of-care setting is rapidly expanding, especially in the fields of emergency medicine (EM) and critical care. Airway management requires rapid confirmation of endotracheal (ET) tube placement, and misplacement can have significant consequences. Several methods for confirmation of tube placement are available, including direct visualization of the vocal cords, chest radiography, auscultation, and end-tidal capnography. End-tidal capnography has been shown to be the most reliable method
☆ No grants or other financial support have been provided. ☆☆ None of the authors have any conflicts of interest to disclose. ★ R.S., E.K., T.K., and W.S. conceived and designed the study. R.S. authored the institutional review board submission, and E.K., T.K., and W.S. provided editorial support. R.S. prepared all study material. R.S., E.K., and W.S. participated in the cadaver laboratory and data acquisition. R.S. managed the data, including quality control. T.K. performed tape review and data collection based on that review. E.K. provided statistical advice and assisted with data analysis. R.S. drafted the manuscript, and all authors contributed substantially to its revision. ⁎ Corresponding author. Department of Emergency Medicine, Wellspan York Hospital, York, PA 17405. E-mail address: [email protected] (R. Stuntz). 0735-6757/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2013.11.032
for determining tube placement; however, its expense may limit availability in some locations. Previous studies have examined the use of transtracheal US (TTUS) to help identify ET tube location [1-4]. Chou et al [5] described a novel protocol, the Tracheal Rapid Ultrasound Exam (TRUE), which used TTUS to confirm ET tube placement as an alternative to end-tidal capnography. The described protocol uses an ultrasonography US probe over the suprasternal trachea in the transverse plane to evaluate for the presence of a hyperechoic airmucosa interface with posterior comet tail reverberation artifact. The presence of one air-mucosa interface with posterior comet tail indicates tracheal intubation, whereas the presence of 2 such interfaces indicates esophageal intubation. In the study performed by Chou et al, this protocol was performed by 2 senior EM residents who had completed all requisite training for US required by their residency. In addition, they received specific training in TTUS, which consisted of a 1-hour didactic session and 8 hours of hands-on training. They were also supervised by an emergency physician with 10 years of emergency US experience who was certified by the Society of Ultrasound in Medicine, Republic of China, Taiwan. In experienced hands, TRUE was shown to be sensitive and specific with short examination times. Other studies investigating the use of US for identification of ET tube location have been
268
R. Stuntz et al. / American Journal of Emergency Medicine 32 (2014) 267–269
performed with experienced sonologists [4,6]. Ultrasound is known to be operator dependent. To our knowledge, no study to date has investigated the role of sonographer experience in correct identification of ET tube placement. The goals of this study are to determine the ability of emergency physicians to successfully identify ET tube location using TTUS and to evaluate the role sonologist experience plays in successful identification of tube placement.
Ultrasound experience
Reported %
0-50 scans 14 51-100 scans 6 101-150 scans 1 N150 scans 8 Total 29
48.3 20.7 3.4 27.6 100
Number–educational level 4-MS4, 6-R1, 3-R2, 1-attending 4-R2, 2-R3 1-R2 1-R1, 1-R2, 1-R3, 1-fellow, 4-attending 4-MS4, 7-R1, 9-R2, 3-R3, 1-fellow, 5-attending
MS4, fourth-year medical student; R1/R2/R3, first/second/third-year EM resident; fellow, emergency US fellow; attending, EM attending.
2. Materials and methods This was a cross-sectional, single-blinded study conducted during a procedural cadaver laboratory. The study was approved by the institutional review board. Participants included EM residents, medical students, and attending physicians. Prior to participation, the study was explained, and participation was made voluntary. One week prior to the study, all participants were given an illustrated instructional handout describing the proper technique for TTUS to identify both tracheal and esophageal intubations. The handout included illustrations taken from the TRUE study showing US-generated images of tracheal and esophageal tube placement. Written instructions were also provided on techniques to obtain adequate images and to correctly interpret the generated images. These instructions were provided to all participants a second time for additional review on the day of the study. Each study participant was de-identified and assigned a study number. Participants were asked to fill out a brief survey describing their level of training, level of US experience, and time spent reviewing the instructional material. The American College of Emergency Physicians recommends a minimum of 150 scans in addition to didactic time dedicated to US education to be deemed competent in emergency US [7]. Therefore, we defined experienced sonologists as those who self-reported performing greater than 150 scans and inexperienced sonologists as those who self-reported performing less than 150 scans. Two cadavers with similar neck and airway anatomy were used as models. One cadaver had an ET tube placed in the esophagus, whereas the second had an ET tube placed in the trachea. They were intubated under direct laryngoscopy by an experienced emergency physician who did not otherwise participate in the study using size 7.5 ET tubes with 10 cc of air inflated into the cuffs. Participants were blinded to the location of the tube, and informed tube placement could be the same or different in both cadavers. Subjects were asked to determine tube placement using TTUS with a high-resolution 13-6 MHz linear transducer (SonoSite M Turbo, Bothell, WA) following the TRUE protocol. Subjects were randomized to start on cadaver A or B and performed their examinations sequentially. They were not allowed to discuss results with other participants. Subjects were not allowed to manipulate the tube in any way. Image interpretation was recorded for all participants. Factors affecting image quality, including gain and depth, were manipulated at the discretion of the participants. Video clips of the examinations were recorded for later review. A brief post– participation survey was completed by each participant to assess the comfort level and confidence regarding accuracy of image acquisition
Table 1 Breakdown of study participants
MS4 R1 R2 R3 Ultrasound fellow EM attending Total
Table 2 Self-reported number of scans performed by study participants
No.
%
4 7 9 3 1 5 29
13.8 24.1 31.0 10.3 3.4 17.2 100
MS4, fourth-year medical student; R1/R2/R3, first/second/third-year EM resident.
and interpretation. Video clips were examined at a later time by the emergency US fellowship director for image quality, time spent on the examination, and accuracy of interpretation of tube location. Prestudy and poststudy surveys were completed for each participant. Data collected from the US director image review included technical adequacy of the study, interpretation of tube location based on images provided for each subject and cadaver, and total examination time for each subject and cadaver. All investigators were subsequently unblinded to correct tube location for the purpose of statistical analysis. Descriptive statistics and χ 2 test were used to analyze the data.
3. Results In total, 29 subjects performed TTUS on 2 cadavers, for a total of 58 scans. All eligible participants chose to participate in the study. Table 1 depicts the levels of training for the study participants. Of the 29 participants, 8 (27.6%) were considered experienced sonologists (Table 2). Only 1 participant (the US fellow) had performed TTUS for evaluation of ET tube location prior to this study. All participants reviewed the educational material, with 62.1% having reviewed the images and protocol within the hour prior to the study. Cadavers were identified as A and B. The ET tubes were placed in the esophagus of cadaver A, and the trachea of cadaver B. Eleven (37.9%) of 29 subjects correctly identified esophageal tube location in cadaver A, and 18 (62.1%) of 29 subjects correctly identified tracheal tube location in cadaver B. These results produce a sensitivity of 62.0% (95% confidence interval [CI], 42.3-79.3) and a specificity of 37.9% (95% CI, 20.7-57.7) for the ability of TTUS to predict the correct placement of an ET tube in a cadaver model. Mean time spent interpreting images for cadavers A and B were 24.73 and 24.89 seconds, respectively (Table 3). Subgroup analysis revealed that 6 of the 8 subjects deemed “experienced sonologists” correctly identified tracheal intubation, and 5 of the 8 correctly identified esophageal intubation. This resulted in better test sensitivity and specificity among the most experienced sonologists, 75.0% (95% CI, 34.9-96.8) and 62.5% (95% CI, 24.5-91.5), respectively. Owing to problems with recording, clips for 3 of the participants were not reviewed and thus excluded from data analysis. Video of the remaining 26 subjects was reviewed, and all but 1 participant obtained images deemed adequate for analysis. Of the recorded images available for review, 96.2% were adequate for interpretation.
Table 3 Time spent scanning each cadaver recorded on clip review by ultrasound fellowship director
Cadaver A Cadaver B
Mean (s)
Minimum (s)
Maximum (s)
Range (s)
SD (s)
24.73 24.89
6 10
76 103
70 93
18.08 20.63
R. Stuntz et al. / American Journal of Emergency Medicine 32 (2014) 267–269
3.1. Limitations This was a small, single-center study, with only 29 participants. In addition, the images from 3 subjects were not available for later review. This study was performed on only 2 cadavers in a single cadaver laboratory, and thus, the results may not be generalizable to the general emergency department population. Neck and airway anatomy were chosen to be similar, so there should not have been limitations on ability to acquire adequate images, and participants did not know the location or pattern of tube placement in the cadavers. Our educational intervention was limited to still images and written instructions, no more than one would obtain by reading the TRUE study. This limitation of education was by design, as we wanted to determine the ability of providers with varying degrees of US experience to use this examination based on the published protocol. We are limited by the fact that US experience level was self-reported.
269
tool, sensitivity and specificity were greatly improved, 97.1% and 100%, respectively [10]. This has been suggested in recently published research, as well [8]. The use of adjuncts to assist in proper identification of ET tube location has also been investigated. Goksu et al [11] looked into the effect of using a stylet to aid in US confirmation of intubation. Stylet use did not result in more accurate identification. Uya et al [12] showed that ET tubes with saline-filled cuffs allowed for successful identification of ET tube location in 39 of 40 cases, with a sensitivity of 96% for identifying tracheal location. Further study is needed to see if similar adjuncts, in combination with dedicated training, would allow for improved sensitivity for this technique. In summary, although most participants were able to obtain adequate images, correct interpretation of the images was poor. More experienced sonologists were more often able to correctly identify tube location. More in-depth education and perhaps proficiency testing should be required before adopting this US modality.
4. Discussion Ultrasound has been previously studied in the confirmation of ET intubation, with recent studies suggesting a TTUS protocol as a promising alternative for confirmation of ET tube placement [5]. This protocol was used with success in a subsequent study by the same authors in real-time intubations of patients undergoing cardiopulmonary resuscitation with similar success [8]. Ultrasound is a tool that can be used by most physicians with minimal training; however, US is known to be operator dependent. A recently published study concluded that airway US for ET tube placement could replace endtidal capnography for ET tube confirmation [9]. Our goals were to determine the ability of emergency physicians to successfully identify ET tube position using TTUS and to evaluate the role operator experience plays in successful identification of tube placement. Most participants in our study obtained adequate images, with 96.2% of obtained images being deemed adequate for interpretation. However, correct interpretation of the images was poor, especially in light of other published data [5,8,9]. Experienced sonologists were able to correctly identify tube location more often; however, even in this subgroup, the sensitivity and specificity fell short of previously reported values, and overlapping CIs do not allow for significance. The consequences of misidentifying ET tube placement can be catastrophic. As US becomes more available, it is important to recognize its limitations in the hands of inexperienced providers. As this study illustrates, even in the hands of experienced sonologists who are comfortable with performing US, new techniques do not fare well without proper education. In one previous study, EM residents were instructed on typical normal tracheal findings on TTUS, as well as findings associated with tracheal intubation. They then evaluated resident ability to identify tube location in cadavers using both static and dynamic methods. They found poor sensitivity (51%) in static identification; however, when used in real time during placement of the ET tube as a dynamic
Acknowledgment We would like to thank Theodore Bell, Barbie Stahlman, and Catherine Kelly for their assistance with data collection, statistical analysis, and manuscript preparation. References [1] Drescher MJ, Conrad FU, Schamban NE. Identification and description of esophageal intubation using ultrasound. Acad Emerg Med 2000;7:722–5. [2] Milling TJ, Jones M, Khan T, et al. Transtracheal 2-D ultrasound for identification of esophageal intubation. J Emerg Med 2007;32(4):409–14. [3] Muslu B, Sert H, Kaya A, et al. Use of sonography for rapid identification of esophageal and tracheal intubations in adult patients. J Ultrasound Med 2011;30(5):671–6. [4] Werner SL, Smith CE, Goldstein JR, et al. Pilot study to evaluate the accuracy of ultrasonography in confirming endotracheal tube placement. Ann Emerg Med 2007;49(1):75–80. [5] Chou HC, et al. Tracheal rapid ultrasound exam (T.R.U.E.) for confirming endotracheal tube placement during emergency intubation. Resuscitation 2011;82(10):1279–84. [6] Galiciano J, Bush AJ, Godambe SA. Use of bedside ultrasonography for endotracheal tube placement in pediatric patients: a feasibility study. Pediatrics 2007;120:1297–303. [7] American College of Emergency Physicians. Policy Statement: Emergency Ultrasound Guidelines. October 2008. [8] Chou HC, et al. Real-time tracheal ultrasonography for confirmation of endotracheal tube pleacement during cardiopulmonary resuscitation. Resuscitation 2013;84(12):1708–12. [9] Osman AB, Chuan TW, Manikam R. A feasibility study on bedside upper airway ultrasonography compared to waveform capnography for verifying endotracheal tube location after intubation. Crit Ultrasound J 2013;5(1):7. [10] Ma G, Davis DP, Schmitt J, et al. The sensitivity and specificity of transcricothyroid ultrasonography to confirm endotracheal tube placement in a cadaver model. J Emerg Med 2007;32(4):405–7. [11] Goksu E, Sayrac V, Oktay C, et al. How stylet use can effect confirmation of endotracheal tube position using ultrasound. Am J Emerg Med 2010;28:32–6. [12] Uya A, Spear D, Patel K, Okada P, Sheeran P, McCreight A. Can novice sonographers accurately locate an endotracheal tube with a saline-filled cuff in a cadaver model? A pilot study. Acad Emerg Med 2012;19(3):361–4.
