External laryngeal manipulation does not”>American Journal of Emergency Medicine (2012) 30, 2005-2010

Brief Report

External laryngeal manipulation does not improve the intubation success rate by novice intubators in a manikin study^?

Nir Samuel MD ^a, Karyn Winkler ^b, Shuny Peled MD ^a,

Baruch Krauss MD ^c, Itai Shavit MD ^a,?

^aDepartment of Pediatric Emergency, Rambam Health Care Campus, Technion Faculty of Medicine, Haifa, 31096, Israel

^bTechnion Faculty of Medicine, Haifa, 31096, Israel

^cDivision of Emergency Medicine, Children’s Hospital Boston and Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA

Received 9 December 2011; revised 7 January 2012; accepted 9 January 2012

Abstract

Background: External laryngeal manipulation (ELM) is a technique used in cases of poor glottic view in direct laryngoscopy. Studies investigating ELM in the pediatric population are lacking. The objective of this study was to examine if use of ELM by inExperienced intubators improves the success rate of pediatric intubation.

Methods: We conducted a randomized, controlled, manikin study comparing intubation using ELM (study subjects) with standard intubation (controls). Study participants were paramedic students. Each participant performed 1 intubation attempt on 3 different pediatric airway manikins, independently. If an optimal Cormack-Lehane glottic view (CLGV) of more than 2 has been obtained, study subjects were previously instructed to perform the intubation using ELM; controls were instructed to continue with standard intubation. Outcome measures were single-attempt intubation success rate, preintubation CLGV, and duration of intubation.

Results: The study group included 13 subjects who performed 39 intubations. In 19 intubations, CLGV of more than 2 had been obtained; and ELM was used. The control group included 14 subjects who performed 42 intubations. In 20 intubations, CLGV of more than 2 was obtained. Median CLGV score improved from 3.5 before ELM to 2 when ELM was used. However, no difference was found between the groups in intubation success rate (10/19 vs 14/20, P = .43); and the duration of intubation was significantly shorter in controls (25.8 vs 37.8 seconds, P b .007).

Conclusions: In this Pediatric manikin study, ELM performed by novice intubators improved Laryngeal view, but lengthened the duration of intubation and did not improve intubation success rate.

(C) 2012

^? Author contributions information: N.S. conceived the idea for the study, designed the study, collected the data, and drafted the manuscript. K.W. assisted in creating the study design and in data collection. S.P. assisted in data collection. B.K. critically reviewed the manuscript. I.S. designed the study, drafted the manuscript, performed the statistical analysis, and reviewed the literature. I.S. has full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

* Corresponding author. 369 P.O. B Nahariya, Israel, 22103. Tel.: +972 50 2063239.

E-mail address: i_shavit@rambam.health.gov.il (I. Shavit).

0735-6757/$ – see front matter (C) 2012 http://dx.doi.org/10.1016/j.ajem.2012.01.010

Introduction

Securing the airway is of major importance in the setting of resuscitation [1,2]. In children, because of their unique anatomy, endotracheal intubation may be difficult to perform especially in the prehospital setting [3].

External laryngeal manipulation (ELM) is a technique used in cases of poor glottic view in direct laryngoscopy [4]. In this technique, an assistant’s hand is placed on the larynx; and then the intubator places his right hand on the assistant’s hand and uses it to maneuver the laryngeal structures while maintaining his own line of sight with the airway opening (Fig. 1A). Once an optimal glottic view is attained, the intubator ensures that an assistant maintains the position of the larynx while the tube is passed (Fig. 1B) [5]. This technique has been shown to be superior to the earlier maneuver of applying backward-upward-rightward pressure on the larynx and to the Sellick maneuver [6]. Studies investigating ELM in the pediatric population are lacking. Previous studies on adult manikins have reported contradic- tory results [1].

The objective of this study was to examine if the ELM technique could be helpful in children. We hypothesized that in conditions of poor glottic view in direct laryngoscopy, using ELM technique will improve the chance for successful intubation and result in shorter intubation time.

Methods

standard technique“>Study design

We conducted a randomized, controlled, manikin study comparing intubation using ELM (study subjects) with standard intubation (controls) in conditions of poor glottic view in direct laryngoscopy. Study participants performed 1 intubation attempt on 3 different pediatric airway manikins, independently. The procedure started with direct laryngos- copy. If an optimal Cormack-Lehane glottic view (CLGV) of more than 2 has been obtained [7], study subjects were

instructed to use ELM for the intubation; controls were instructed to continue with the intubation. The study was conducted at the simulation laboratory of the Rambam Health Care Campus in Haifa, Israel; and the Rambam Health Care Campus ethics committee approved the study with a consent waiver.

Study participants

Study subjects were emergency medical technicians undergoing training for paramedic status. The study was conducted on the first of a 2-day pediatric resuscitation course taught by pediatric emergency physicians who also served as study investigators. Before the study, participants completed courses in Advanced Cardiac Life Support and in Prehospital Trauma Life Support as part of their paramedic training curriculum. None of the study subjects performed pediatric intubation (or a simulation of it) before the study.

Randomization process

Participants were randomized into the 2 arms of the study using an allocation sequence created by a computerized random-number generator (StatsDirect statistical software, version 2.6.6; StatsDirect Limited, Cheshire, UK). The order of the manikins on which each participant performed the procedure was also randomized using a randomized allocation sequence created by the same software.

Study techniques

Standard technique

The procedure started with direct laryngoscopy. Once an optimal glottic view was optimized, the participant was previously instructed to grade the CLGV and to perform one tracheal intubation attempt (using standard equip- ment, Appendix).

ELM technique

The procedure started with direct laryngoscopy. Once an optimal glottic view obtained, the participant was instructed

Fig. 1 External laryngeal manipulation. The intubator guides the position and pressure exerted by the assistant’s hand on the larynx to optimize glottic view.

difficulty of intubation and glot”>to grade the CLGV and to perform one tracheal intubation attempt if the CLGV was 1 or 2 (using standard equipment, Appendix). If the CLGV was 3 or 4, the participant was previously instructed to use ELM by asking a research investigator (N.S.) to place his right hand on the manikin larynx [5]. The participant then placed his right hand on the assistant’s hand and maneuvered the manikin’s larynx while maintaining his own line of sight with the airway opening (Fig. 1A). Once the glottic view has been optimized, the assistant was asked to take over and maintain the position of the larynx while the participant grades the preintubation CLGV and passes the tube (Fig. 1B). Standard equipment was used (Appendix). The assistant of the ELM was passive through the whole procedure and did not intervene with the procedure or provide any consultation or recommenda- tion. The same assistant was used for all ELM procedures in the study.

Outcome measures and data collection

Primary outcome measure

The primary outcome measure was success rate in a single intubation attempt. Success was defined as endotra- cheal tube (ET) placed in the trachea as verified by a study investigator. A failed intubation attempt was defined as an attempt in which the trachea was not intubated or in which intubation of the trachea required longer than 60 seconds to perform [8].

Secondary outcome measures

1. Preintubation CLGV. The Cormack and Lehane classifications are as follows: grade 1, full view of the glottis; grade 2, only posterior commissure visible; grade 3, only epiglottis visible; and grade 4, no glottic structure visible [7]. Preintubation CLGV was determined by the participants and marked on a standard data form by a research investigator (N.S.).
2. Duration of intubation. The duration of each endotracheal intubation attempt was defined as the time taken from insertion of the blade between the lips until the ET was deemed to be correctly positioned by the participant [9]. In cases where the participant was unsure as to the position of the ET, the time taken to connect the ET to the self-inftating bag and inftate the manikin’s lungs was included in the duration of the attempt [8].

Study instruments

Three pediatric airway manikins in which the larynx could be easily manipulated externally were selected for the study:

1. Infant size manikin (Nasco LifeForm infant airway management trainer LF03623U, Salida, CA.).
2. Child size manikin (Nasco LifeForm child airway management trainer LF03609U, Salida, CA.).
3. Child size manikin with neck immobilization (pediat- ric intubation trainer, Laerdal, Wappingers Falls, NY; neck was rigidly fixed to the table with a tape).
   

   Difficulty of intubation and glottic view

Before the study, we estimated the difficulty of intubation and the laryngeal visualization of each airway manikin. We asked 8 experienced pediatric emergency specialists to separately perform 1 intubation attempt on each of the 3 airway manikins. These experts were also asked to grade the preintubation glottic view according to the CLGV. The order of the manikins on which each specialist performed the procedure was randomized using a randomized allocation sequence created by a computerized random-number generator (StatsDirect statistical software, version 2.6.6; StatsDirect Limited).

The following single-attempt success rates were obtained: 7 (87.5%) of 8 for the infant airway manikin, 6 (75%) of 8 for the child airway manikin, and 4 (50%) of 8 for the child airway manikin with neck immobilization. Overall intuba- tion success rate was 17 (70.8%) of 24. The following median glottic views were obtained: 1.5 for the infant airway manikin (4 experts graded CLGV 2, and 4 experts graded CLGV 1), 2.5 for the child airway manikin (4 experts graded CLGV 3, 2 experts graded CLGV 2, and 2 experts graded CLGV 1), and 3.5 for the child airway manikin with neck immobilization (4 experts graded CLGV 4, 1 expert graded CLGV 3, 2 experts graded CLGV 2, and 1 expert graded CLGV 1). Overall, these specialists had a success rate of 9 (37.5%) of 24 intubations with poor laryngeal view (CLGV of more than 2).

Study procedure

Participants received a 30-minute lecture by a research investigator (I.S.) on difficult intubation in children. The research investigator explained and demonstrated the standard technique and the ELM technique in detail. After the lecture, each participant practiced standard intubation and intubation using ELM on 2 practice manikins (infant intubation model, Laerdal; child intubation head, Armstrong Medical, Lincoln- shire, IL) using standard equipment (Appendix). During the practice of the 2 techniques, participants were taught, assisted by illustrations, how to grade the CLGV. Practicing the 2 techniques was ended when all participants were satisfied with their understanding of the 2 methods and their understanding of CLGV grading. Thereafter, participants were randomly divided into the 2 arms of the study; and the sequence of manikins in which each participant performed the intubation was randomly determined.

Immediately after, each participant entered the study

room in which the 3 study manikins were placed on a table. The procedure started with direct laryngoscopy. If an optimal CLGV of 1 or 2 has been obtained, participants of both groups were instructed to perform standard intubation. If an optimal CLGV of 3 or 4 has been obtained, participants of

the subject group were instructed to use ELM for the intubation; controls were instructed to continue the intuba- tion without using ELM. The study investigator recorded preintubation CLGV and the timing of each attempt, and verified tube placement and the success of intubation. As soon as the first manikin’s intubation attempt was completed, the participant was asked to perform 1 intubation attempt on the second manikin. Once the second procedure was completed, participant was asked to perform 1 intubation attempt on the third manikin.

Only the study participant, the study investigator (N.S.), and the study assistant (medical student, K.W.) were present in the study room. The study investigator and the study assistant did not intervene with the procedure or provide any consultation or recommendation. Participants could not watch other perform the procedure and were not allowed to ask the investigator or the assistant any question. When a participant exited the study room, he was not allowed to contact the other participants until the study was completed.

Statistical analysis

Data for the success of 1-attempt tracheal intubation were analyzed using ?2 test. Data for the duration of 1-attempt

tracheal intubation were analyzed using the unpaired Student t test. The Mann-Whitney U test was used to test the differences in glottic view. All statistics were calculated using the StatsDirect statistical software (version 2.6.6; StatsDirect Limited).

Results

All 27 paramedic students approached by the principal investigator agreed to participate in the study.

Demographic data

The study group consisted of 13 participants with a mean age of 27.9 years and a male to female ratio of 11:2. The control group consisted of 14 participants with a mean age of 28 years and a male to female ratio of 12:2. In total, the 13 study subjects and the 14 controls performed 39 and 42 intubations, respectively. All intubations were completed before the 60-second time limit.

Glottic view* 3-4

tic View* 3-4

Intubation without ELM (n = 22)

One-attempt Success rate 22/22

Laryngoscopy (n = 42)

Laryngoscopy (n = 39)

Randomization

Study subjects(n = 27)

Glottic view* 1-2

Glottic view* 1-2

Intubation without ELM (n = 20)

Study subjects (n = 13)

Control subjects (n = 14)

One-attempt Success rate 18/20

Difficult intubation

Glot

Intubation with ELM (n = 19)	Intubation without ELM (n = 20)
One-attempt Success rate 10/19	One-attempt Success rate 14/20

*Cormack and Lehane classification

Fig. 2 Study ftow chart.

Study group (intubation using ELM)		Control group (standard Intubation)
No. of single-attempt intubations with optimal glottic view a N2	19	20
Infant AW manikin	4	5
Child AW manikin	7	5
Child AW manikin with neck Immobilization	8	10
Optimal glottic view prior ELM (median)	3.5	Not relevant
Optimal glottic view prior intubation (median)	2	3
Total time for intubation (mean +- SD, seconds)	37.8 +- 15.5	25.8 +- 13.7
Successful intubations in 1 attempt (%)	10/19 (52.6)	14/20 (70)
Infant AW manikin (%)	4/4 (100)	5/5 (100)
Child AW manikin (%)	3/7 (42.8)	4/5 (80)
Child AW manikin with neck immobilization (%)	3/8 (37.5)	5/10 (50)
AW indicates airway. a Cormack and Lehane classification.

Intubations with good glottic view (CLGV 1-2)

Table 1 Comparison between the ELM technique and the standard technique

In 20 intubations by the study subjects, an optimal CLGV of 1 or 2 was obtained; and intubation continued without using ELM. Eighteen (90%) intubations were successful (Fig. 2).

In 22 intubations by the controls, an optimal CLGV of 1 or 2 was obtained; and intubation continued without using ELM. All (100%) intubations were successful.

Intubations with poor glottic view (CLGV 3-4)

In 19 intubations by the study subjects, an optimal CLGV of 3 or 4 was obtained; and intubation continued using ELM. Ten (52.6%) intubations were successful (Fig. 2, Table 1).

In 20 intubations by the controls, an optimal CLGV of 3 or 4 was obtained; and intubation continued without ELM. Fourteen (70%) intubations were successful.

Comparison between the groups

Median CLGV score improved from 3.5 before laryngeal manipulation to 2 when laryngeal manipulation was used. No differences in intubation success rate between study subjects and controls were found (10/19 vs 14/20, P = .43). Controls had shorter duration of intubation compared with study subjects (25.8 vs 37.8 seconds, P b .007).

Discussion

This small study is the first to examine the utility of ELM in a pediatric model and to compare intubation using ELM with standard intubation. We found that in scenarios of difficult intubation, ELM performed by novice intubators improved laryngeal view, but lengthened the duration of intubation and did not improve the success rate of intubation.

Our study supports current evidence that ELM improves laryngeal view in conditions of difficult intubation [6,9,10]. However, the findings of this manikin study raise doubts regarding the role of this technique in the setting of emergent intubation [4]. In particular, our results do not support using ELM by novice intubators who perform emergent pediatric intubation.

Our study has several limitations. We selected specific pediatric airway manikins in which the larynx could be easily manipulated externally. However, it is possible that these study instruments may not reftect clinical practice. There- fore, the applicability of our data to a real pediatric intubation is unclear. Because the study participants were novice intubators in regard to pediatric intubation, these results cannot be extrapolated to more experienced intubators.

Because we aimed to simulate the scenario of emergent intubation, the number of intubation attempts was limited to one. It is theoretically possible that had we allowed more than one attempt per manikin, the number of attempts until successful intubation would be lower in the ELM group compared with controls.

Conclusion

In this pediatric manikin study, ELM performed by inexperienced intubators improved laryngeal view, but length- ened the duration of intubation and did not improve intubation success rate.

Appendix A. Equipment for pediatric endotracheal intubation

• Miller 1 Laryngoscope blade and handle (Truphatek International Limited, Netanya, Israel)
• A 4.5-mm OD cuffed ETT (Portex, Smiths Medical International Ltd, Hythe, Kent, UK)
• ETT stylets (Portex, Smiths Medical International Ltd)
• Infant size self-inftating bag-valve system (Ambu Pediatric, Ambu Inc, Glen Burnie, MD, USA)

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