Journal of Emergencies, Trauma, and Shock
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 Table of Contents    
Year : 2021  |  Volume : 14  |  Issue : 4  |  Page : 207-210
How many ultrasound examinations are necessary to gain proficiency in accurately identifying the nerves of the brachial plexus at the level of the interscalene space?

1 University of South Florida Morsani College of Medicine, Tampa, FL, USA
2 The Emergency Resources Group, Jacksonville, FL, USA
3 TeamHealth Special Operations, Knoxville, TN, USA
4 University of South Florida, Division of Emergency Medicine, Tampa General Hospital, Tampa, FL, USA

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Date of Submission31-Jan-2021
Date of Acceptance14-Oct-2021
Date of Web Publication24-Dec-2021


Introduction: There has been a trend toward the use of alternative treatments to opioids for adequate pain management. This has paralleled a growing interest in the utilization of bedside point-of-care ultrasonography to guide placement of regional anesthesia in the emergency department. The purpose of this study was to establish the number of supervised examinations required for an emergency medicine resident to gain proficiency in accurately locating and identifying the nerves of the brachial plexus at the level of the interscalene space. Methods: Proficiency was defined as the number of attempts a resident required to accurately locate and identify the nerves of the brachial plexus on 10 separate, consecutive examinations. Didactic education was provided prior to the study and residents also participated in two instructional hands-on ultrasound examinations prior to the commencement of initial data collection. Count data are summarized using medians, means, and ranges. Random effects negative binomial regression was used for modeling panel count data where negative coefficients indicate increase in proficiency. Results: A total of 24 emergency medicine residents were enrolled in the study. Fourteen males and ten females participated. There were nine PGY-1 residents (37.5%), nine PGY-2 residents (37.5%), and six PGY-3 residents (25%). The median number of required supervised attempts and range for correctly performing both steps in the identification of the nerves of the brachial plexus was 2 (range 2–12). The median starting confidence level was 2 (range 1–4), and the median ending confidence level was 4 (range 1–5). Increases in confidence from start to finish were found to be statistically significant (P < 0.001). Conclusion: Emergency medicine residents are easily adept in the identification of the nerves of the brachial plexus at the level of the interscalene space following two supervised examinations. Residents made steady gains in confidence and proficiency throughout the study; statistical analysis found a significant association between the two.

Keywords: Brachial plexus, interscalene space, supraclavicular fossa, ultrasound

How to cite this article:
Shteyman A, Jackson SA, Campbell TA, Derr C. How many ultrasound examinations are necessary to gain proficiency in accurately identifying the nerves of the brachial plexus at the level of the interscalene space?. J Emerg Trauma Shock 2021;14:207-10

How to cite this URL:
Shteyman A, Jackson SA, Campbell TA, Derr C. How many ultrasound examinations are necessary to gain proficiency in accurately identifying the nerves of the brachial plexus at the level of the interscalene space?. J Emerg Trauma Shock [serial online] 2021 [cited 2022 May 16];14:207-10. Available from:

   Introduction Top

Shoulder and arm injuries are common complaints in the emergency department and frequently require the use of procedural sedation for the management of pain during reduction attempts. Effective procedural sedation is time-consuming, carries the risks associated with the administration of light anesthesia, and requires the presence of a second provider to monitor the patient during the procedure.[1] Opiates are considered the gold standard for pain control but have their own associated risks, and may not be the most appropriate intervention in the acute care setting.[2] Case studies have described how nerve blocks have quickly and safely alleviated pain in patients with traumatic injuries and allowed for their work-up to continue without delay.[1],[3] Nerve blocks have been shown to be very effective for various injuries given their immediate effect, lack of side effects, and relative safety. In addition, ultrasound-guided regional anesthesia was associated with a decreased length of stay in ED patients presenting with anterior shoulder dislocations when compared to procedural sedation.[2],[4] In fact, the use of ultrasound has been found to be a superior method when compared to traditional landmark-based nerve identification and localization.[5],[6] To provide nerve blocks in the emergency department ED setting, studies have looked at training requirements for emergency medicine residents and foreign medical students in order to achieve competency in performing these procedures.[6] While no training standards currently exist,[7] ongoing studies indicate that short lectures followed by hands-on instruction adequately train emergency physicians to locate relevant structures using bedside ultrasound.[8],[9],[10],[11]

   Methods Top

The purpose of this study was to establish the number of supervised examinations required for an emergency medicine resident to gain proficiency in accurately locating and identifying the nerves of the brachial plexus at the level of the interscalene space using a two-step technique.

The primary study endpoint was to determine the median number of attempts at which the participants correctly located and identified, 100% of the time, the nerves of the brachial plexus for ten consecutive novel OSCE examinations; at this point, the resident was deemed proficient. The secondary study endpoint was the measurement of the resident's confidence in his or her ability to correctly locate and identify, 100% of the time, the nerves of the brachial plexus.

This study was constructed as a prospective, interrupted, time-series design without a control group and was formally approved by the University of South Florida Institutional Review Board prior to its implementation. The participants in the study were current residents enrolled in the emergency residency program at the University of South Florida. The study was conducted at Tampa General Hospital in Tampa, Florida, from October 30, 2013 to November 6, 2013. Due to the descriptive nature of this study, sample size calculations were not performed. The emergency medicine program is a PGY1–3 format that enrolls 10 residents per year. Resident participation in this study was voluntary, and informed consent was obtained prior to the start of the study.

The participants received a 1-h introductory didactic on brachial plexus anatomy, sonographic techniques, and the proper identification of the nerves. This was followed by two hands-on instructional examinations where the resident identified the nerves of the brachial plexus at the level of the interscalene space with the help of an instructor. During the didactic and hands-on skills stations, the participants were instructed using a two-step technique for locating the nerves of the brachial plexus at the interscalene space using the following method: first, the transducer was placed in the supraclavicular fossa in the transverse orientation. The subclavian artery was then identified in cross-section atop the first rib. Posterolateral to the subclavian artery, the nerves of the brachial plexus were identified as a group of round hypoechoic structures [Figure 1]. Once identified, the nerves were then followed cephalad up the neck to the level of the anterior and middle scalene muscles (step 2) where they were identified as three round hypoechoic spheres (C5, C6, and C7) [Figure 2].
Figure 1: The first step in performing the examination: identification of the brachial plexus at the level of the supraclavicular fossa

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Figure 2: Step 2 in performing the examination: identification of the brachial plexus at the level of the anterior and middle scalene muscles

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The instructors were EM physicians experienced in POCUS with additional training in ultrasound-guided regional anesthesia. A total of six instructors supervised examinations. The US experience of the instructors ranged from 15 months and 209 US performed to an expert with more than 14 years of experience, over 16,000 US performed and who was a Registered Diagnostic Medical Sonographer with certification in abdominal US. To ensure agreement, the expert scanned the models with each supervising instructor prior to the start of the trainee US sessions.

The models for the OSCE examinations were volunteer members comprised of medical students, family members, and/or nurses. The ultrasound machines used in the study were the Sonosite M-Turbo, SonoSite MicroMaxx, and Sonosite Edge (SonoSite Inc – US, Bothell, Washington 98021). The transducers used were the Sonosite L25 × 6–13MHz, 6 inch, linear array transducer for the M-Turbo and Edge Models, and the L38e 5–10MHz, 9 inch, linear array transducer for the MicroMaxx.

Prior to performing an individual OSCE session, each participant rated his or her confidence level in correctly locating and identifying the nerves of the interscalene brachial plexus with ultrasound using the two-step technique. A five-point Likert scale was used (1 = I always have difficulty, 2 = I often have difficulty, 3 = I sometimes have difficulty, 4 = I rarely have difficulty, and 5 = I never have difficulty)[10] [Table 1]. Each resident then performed the examination independently where they were required to correctly locate and identified the nerves at the level of the scalene space using the previously described two-step technique.
Table 1: Level of confidence

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An attempt at identification consisted of the nerves being identified dynamically on the US screen by the study participant as they were scanned by the participant without prompting from the instructor. Correct or incorrect identification for each step was then recorded at that time by the instructor on a data collection sheet. No images were recorded or reviewed at a later date. Following the assessment, if the participant was incorrect, the instructor educated the participant in ways to improve their technique and identification. This was demonstrated using the same model that the participant had just scanned.

Following an attempt at identification, the participant then imaged the contralateral side of the same model. After the second attempt, the participant rotated to a new model and new instructor. Each model therefore had both the right and left sides scanned by each participant unless an uneven number of exams were performed. Each participant scanned both sides of one model for their two initial supervised examinations. This was then followed by a minimum of five additional models for the ten independent assessments needed for the study. Each model's right or left side was only used once by each participant. Other study participants were not allowed to observe during the scanning process.

The residents' ability to correctly identify the nerves in both steps was recorded and then analyzed to determine the median and mean number of examinations required for an emergency medicine resident to become proficient and feel confident in his or her ability to correctly identify the nerves of the brachial plexus.

Study participants were to be excluded if they were determined to have individually completed more than 10 brachial plexus nerve examinations prior to the onset of the study or if they simply did not wish to participate. No participants met this criteria as no residents had previously imaged the brachial plexus. Residents who did not wish to participate in the study still received education in regard to the proper identification of the nerves and the proper techniques required to perform the blockade of the nerves of the brachial plexus.

The results of the data were analyzed by statisticians at the University of South Florida. A negative binomial regression coefficient was used to describe the data.

   Results Top

Proficiency was defined as the number of attempts required for a resident to be able to correctly identify the nerves of the brachial plexus for 10 consecutive examinations. Data were modeled using negative binomial regression, and P < 0.05 was considered statistically significant.

Complete data for the number of attempts, confidence, gender, and years in practice were available for 24 residents. Fourteen male and ten female residents participated. The median years in practice were 2 (range 1–3), with 9 (37.5%) in year 1, 9 (37.5%) in year 2, and 6 (25%) in year 3.

The median number of attempts required before reaching proficiency in correctly identifying the brachial plexus nerves at the level of the interscalene space for both the first and second steps of the examination was 2. In addition, both steps had the same range of between 2 and 12 examinations. The mean number of attempts before reaching proficiency was also identical at 2.7. The median starting confidence on a scale of 1–5 was reported as a 2 for both steps, and the median confidence level reported at the end of the study was 4 for both steps. On average, residents reported an increase in confidence level of 1.5 points between the start and end of the study. Residents who required >10 attempts did not have significantly higher confidence scores at the end of the study than residents who performed only ten examinations. Negative binomial regression identified a significant association between confidence and proficiency (P = 0.009), suggesting that the confidence increased as the number of performed ultrasound examinations increased.

   Discussion Top

Proficiency in identifying of the nerves of the brachial plexus at the level of the interscalene space was found to be rapidly attainable by residents using a two-step technique. There was a statistically significant correlation between confidence at the start of the study and the number of supervised attempts before achieving proficiency. It may be reasonable to conclude that fewer than ten supervised examinations are sufficient for a resident at any PGY level to achieve adequate proficiency in identifying the nerves of the brachial plexus for the purpose of using regional anesthesia for pain management in the acute setting. However, this study does not suggest that physicians are proficient in the technique of regional anesthesia, only in the location of the neuroanatomy. Future studies would need to address the number of supervised examinations needed to become proficient at the hand-needle–eye coordination and manual skills needed to perform the block.

To date, literature in emergency medicine has failed to produce definitive recommendations for training requirements related to proficiency in the use of ultrasound-guided techniques for delivery of analgesia in place of the traditional, landmark-based approaches. This study set out to establish a framework upon which to continue to develop guidelines for training emergency medicine residents in ultrasound-guided regional anesthesia.


The study was limited by a small sample size of only 24 residents with no power calculation. A future study would be strengthened by adding a greater number of participants through a multicenter study of emergency medicine residency programs. On a more positive note, there was a relatively even distribution in terms of the level of PGY training of participants used in the study. In addition, the size of each emergency medicine residency class at the University of South Florida (10 residents per year) is similar to that of many other emergency medicine residencies in the United States.

Another limitation is that our study used a healthy population of models with normal body mass index which may have made identification of the neuroanatomy less difficult. Neuroanatomy in the general ED patient population can be quite variable in appearance due to body habitus, muscle atrophy in elderly patients, tissue edema, air in the soft tissue from trauma, and anatomic anomalies.

Finally, this study only examined the procedure of learning sonographic anatomy and did not address two other important educational milestones that must be achieved by learners when performing regional anesthesia: visual-spatial skills and motor skills. Failure of these two skills may lead to failure of the block or complications. Complications often occur when the learner fails to visualize the needle tip while advancing toward the target which may inadvertently cause nerve injury, pneumothorax, venous puncture, or unintentional neuraxial blockade.

   Conclusion Top

Emergency medicine residents require relatively little training and supervision before achieving proficiency in identifying the nerves of the brachial plexus with ultrasound. Confidence grew rapidly among all participants in the study. Hence, relatively little didactic and supervisory instruction may be required to train residents in the sonographic skills needed to be proficient in an increasingly useful pain-management modality.

Residents should, however, be adequately trained in the basics of ultrasound principles, anatomy, anesthesia, needle guidance, and patient safety before learning more complex interventions. Future expansions on this study may aim to integrate such concepts into a formalized educational protocol, and thus lead to safer and more efficient pain management in the ED.


A special thank you to the following individuals who contributed to the development, data collection, and statistical analysis during this study: Raymond Merritt DO, Zuheily Closser MD, Leah Boyette MD, Branko Miladinovic PhD.

Research quality and ethics statement

This study was approved by the Institutional Review Board / Ethics Committee no CR7_Pro00004381 . The authors followed applicable EQUATOR Network (”http:// guidelines during the conduct of this research project.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Banerjee S, Acharya R, Sriramka B. Ultrasound-guided inter-scalene brachial plexus block with superficial cervical plexus block compared with general anesthesia in patients undergoing clavicular surgery: A comparative analysis. Anesth Essays Res 2019;13:149-54.  Back to cited text no. 1
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Rueda Rojas VP, Meléndez Flórez HJ, Orozco Galvis E. Analysis of previous training with simulated models on the success rate of ultrasound-guided supraclavicular block. Prospective cohort study. Rev Esp Anestesiol Reanim (Engl Ed) 2019;66:241-9.  Back to cited text no. 10
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Correspondence Address:
Dr. Tabitha Anne Campbell
489 Hood Ln, Wilder, TN 38589
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JETS.JETS_141_20

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