a b s t r a c t

Introduction: Endotracheal intubation using a Macintosh laryngoscope requires the head to be posi- tioned in a modified Jackson position, slightly reclined and elevated. Intubation of trauma patients with an in- jured neck or spine is therefore difficult, since the neck usually cannot be turned or is already immobilized in order to prevent further injury. The iGEL supraglottic airway seems optimal for such conditions due to its blind insertion without the need of a modified Jackson position.

Methods: Prospective, randomized, crossover study in 46 paramedics. Participants performing standard intuba- tion and blind intubation via iGEL supraglottic airway device in three airway scenarios: Scenario A – normal air- way; Scenario B – manual inline Cervical immobilization, performed by an independent instructor; scenario C: cervical immobilization using a standard Patriot cervical extraction collar.

Results: In Scenario A, nearly all participants performed ETI successfully both with MAC and iGEL (100% vs. 95.7%). The time to intubation (TTI) using the MAC and iGEL amounted to 19 [IQR, 18-21]s vs. 12 [IQR, 11-13]s (P b 0.001). Head extension angle as well as tooth compression were significantly better with the iGEL compared to the MAC (P b 0.001). In scenario B and C, the results with the iGEL were significantly better than with MAC for all analyzed variables (TTI, success of first intubation attempt, head extension angle, tooth compression and VAS scores).

Conclusion: We showed that blind intubation with the iGEL supraglottic airway was superior to ETI performed by paramedics in a simulated cervical immobilization scenario in a manikin in terms of success rate, time to definite tube placement, head extension angle, tooth compression, and rating.

(C) 2016

1. Introduction

Securing an airway is pivotal in an emergency situation, with endo- tracheal intubation being the gold standard. Endotracheal intubation with a standard endotracheal tube using a Macintosh laryn- goscope (MAC) usually requires the head to be positioned in a modified Jackson position (“sniffing”), slightly reclined and elevated. In this position, the axis of pharynx, larynx, and trachea nearly align, thereby facilitating the entry of the ETT through the glottis into the trachea. Intubation of trauma patients with an injured neck or spine is therefore difficult, since the neck usually cannot be turned or is already immobilized in order to prevent further injury [1,2]. Conventional ETI of trauma patients with cervical injuries always poses the risk of cervical dislocation, prolapse, or nerve damage.

* Corresponding author at: Department of Emergency Medicine, Medical University of Warsaw, Lindleya 4 Str, 02-005 Warsaw, Poland.

E-mail address: [email protected] (L. Szarpak).

In the past decades, several devices have been developed that can be inserted blindly without the use of a laryngoscope and therefore the need of putting the head in the modified Jackson position. The Combitube was the first widely used supraglottic airway device [3,4]. Recently, more devices of that kind have been developed, most of them can be inserted blindly and usually enter the esophagus [5,6]. The major advantages of these devices are that they can be inserted by non-airway specialists with relatively little formal training [7], that sufficient ventilation and ox- ygenation is feasible and safe, and that the rate of complications is compa- rable to ETT [8]. The ERC and AHA guidelines recommend supraglottic airway control in circumstances where ETI is not possible or not within the competency of the individuals managing the patient’s airway [9,10]. The iGEL (Fig. 1) is a supraglottic airway device that has been devel- oped in 2007 and is used in anesthesia and resuscitation across the globe [11-13]. Its biggest difference to similar devices is that it uses a soft, gel-like, non-Inflatable cuff, designed to provide an anatomical im- pression fit over the laryngeal inlet. This design prevents compression and displacement trauma as seen in cuff-based devices and can be

http://dx.doi.org/10.1016/j.ajem.2016.11.064

0735-6757/(C) 2016

Power calculation“>P. Gawlowski et al. / American Journal of Emergency Medicine 35 (2017) 484–487 485

Fig. 1. i-GEL supraglottic airway device.

placed significantly faster than other Supraglottic airway devices [14]. Due to its blind insertion, the iGEL seems optimal for securing an airway in patients with neck or spine trauma. Other advantages comprise min- imizing compression of the mucosa or non-impaired blood flow due to lack of cuff balloons. The iGEL can be used safely in patients undergoing lumbar surgery even in prone position [15]. However, literature on the use in trauma patients is scarce, with the iGEL not having been evaluat- ed with this regard.

The aim of this study was therefore to compare the success rate, the time to definite tube placement, head extension angle, tooth compres- sion, and rating of ETI using the Macintosh laryngoscope and blind intu- bation using the iGEL supraglottic airway performed by paramedics during cervical immobilization in a manikin.

1. Methods

This was a prospective, randomized, crossover study. The study was approved by Institutional Review Board of the Polish Society of Disaster Medicine (Approval: IRB N16.08.2016). Following written informed consent, 46 paramedics with no prior training in intubation using supraglottic airway devices and with at least one year experience in emergency medicine were recruited. The study was conducted in August 2016.

Study scenarios

Each participant performed intubation on an airway assessment training manikin (BT-CSIE; BT Inc., Republic of Korea), placed on a trau- ma stretcher (M-1(R) Roll-in System – Ambulance Cots by Stryker). Three airway scenarios were randomly cycled:

1. scenario A: normal airway (without cervical immobilization);
2. scenario B: manual inline cervical immobilization, performed by an independent instructor;
3. scenario C: cervical immobilization using a standard Patriot cervical extraction collar (Ossur Americas, Foothill Ranch, CA, USA), applied to the manikin’s neck by an independent instructor.

ETI was performed using a standard Macintosh laryngoscope with blade #3 (MAC; Mercury Medical, Clearwater, FL, USA), and an iGEL supraglottic airway device, size 4 (iGEL; Intersurgical Ltd., Berkshire, UK, Fig. 1). A standard 7.5 cuffed endotracheal tube lubricated with sil- icon was used. For intubation with MAC, also tubes used were fashioned with a hockey-stick shaped stylette and prepared by an experienced se- nior researcher in airway management. If necessary, study participants were allowed to adjust the stylette by their own needs.

Study conduct

Prior the study, all participants completed a 30-minute training ses- sion, which included an introduction to the anatomy and physiology of

the airway and techniques of intubation using different supraglottic air- way devices. After the training session, a computerized software [www. randomizer.org] was used to randomly assign the volunteers to 6 groups. The first group conducted intubation using MAC in scenario A; the second group using MAC in scenario B; the third group, using MAC in scenario C; the fourth group, using iGEL in scenario A; the fifth group, using iGEL in scenario B; and the sixth group using iGEL in sce- nario C. After completing the run, participants had a 10-minute break before attempting intubation using the next method. Participants were not allowed to watch each other during any of the intubation at- tempts to avoid learning effects throughout the procedure. Participants had a maximum of one attempt in each condition.

Measurements

The primary outcome was time to definite intubation (TTI), defined as the time point from first contact with the device until first successful ventilation of the lungs. Additionally, in case of blind intubation, the time was also recorded from first contact with iGEL device until success- ful placement of the device. The time was recorded using a stopwatch. If the tube was not placed correctly or the lungs were not inflated correct- ly, the attempt was defined as a failure. Moreover we measured head extension angle and force on incisors (N) by indicators on the manikin. After each attempt, the participants were asked to assess the subjective opinions about the difficulty of the procedure on a Visual analogue scale (VAS) with the score from 1 (extremely easy) to 10 (extremely difficult).

Power calculation

Based on pilot data, the following assumptions were made to calcu- late the number of participants to be included: we used an alpha risk of 0.05, and a beta risk of 0.2 for calculation of sample size. The success rate of first ETI attempt in manual in-line stabilization in pilot data amounted to 86.5% vs. 95.5% in the MAC and iGEL, respectively. Using the t-test, paired, two-sided, at least 35 participants were required and randomized to the respective groups with a 1:1 ratio.

Statistical analysis

All statistical analyses were performed with the use of the Statistica 12 EN for Windows software (StatSoft, Inc.; Tulsa, OK, USA). Data were presented as median and interquartile range (IQR); mean and standard deviation (+-SD); or number and percent (%). Normal distribution was confirmed by the Kolmogorov-Smirnov test. T-test for paired observa- tions was applied for data with normal distribution, and the Wilcoxon test for paired observations in the case of data with non-normal distri- bution. In order to compare TTI the Wilcoxon test for paired observa- tions was used. The McNemar test was applied to evaluate differences in the success of intubation, and the Stuart-Maxwell test allowed to compare the degree of pressure distribution, head extension angel, and the VAS score. All statistical tests were two-sided. The results were considered statistically significant at P b 0.05.

1. Results

A total of 46 paramedics (20 female, 43.5%) participated in this study. All subjects worked in teams of emergency medical services. Mean age was 31.5 +- 6.5 years, and mean work time experience was

5.4 +- 3.2 years.

Scenario A: normal airway

Nearly all participants performed intubation successfully both with MAC and iGEL (100% vs. 95.7%, respectively; Table 1). The TTI using the MAC and iGEL varied and amounted to 19 [IQR; 18-21]s vs. 12

486 P. Gawlowski et al. / American Journal of Emergency Medicine 35 (2017) 484–487

Table 1

Scenario A: normal airway.

Parameters	MAC	iGEL	P-value
Time to intubation (s)	19 [18-21]	12 [11-13]	P b 0.001
Success of intubation n (%)	46 (100%)	44 (95.7%)	P = 0.722
Head extension angle	18 [15-23]	7 [5-10.5]	P b 0.001
Tooth compression force [N]	30 [27-33]	14 [13-15]	P b 0.001
VAS score	2.5 [2-4]	2 [2-3.5]	P = 0.814

[IQR; 11-13]s, respectively (Fig. 2). Median time to placement iGEL was 5 [IQR; 4-6] seconds. Head extension angle as well as tooth compression (Fig. 3) were significantly better with the iGEL than with the MAC (P b 0.001).

Scenario B: cervical manual in-line stabilization

During intubation with manual in-line stabilization scenario (sce- nario B), the results with the iGEL were significantly better than with MAC (P b 0.05) for all analyzed variables (TTI, success of first intubation attempt, head extension angle, tooth compression and VAS scores) (Table 2). Time to iGEL placement was 5 [IQR; 5-6] seconds.

Scenario C: cervical immobilization using cervical extraction collar

100% of participants performed successful intubation with the iGEL, but only 82.6% with MAC (Table 3). The TTI using the MAC and the iGEL varied and amounted to 24 [IQR; 21-27]s vs. 13 [IQR; 11-14]s, respec- tively (Fig. 2). Head extension angel, tooth compression, and VAS score were significantly better with the iGEL than with the MAC (P b 0.001).

1. Discussion

We hereby showed that the iGEL supraglottic airway is a suitable de- vice for paramedics to secure an airway in patients with cervical spine immobilization, during manual immobilization as well as during immo- bilization using a cervical extraction collar.

The iGEL airway has become increasingly popular in recent years in preclinical medicine due to its ease of use and the absence of balloons to be inflated. Also, ETI performed by inexperienced paramedics is associ- ated with a low success rate [16] and often paramedics do not have the necessary level of regular training. In contrast, supraglottic airway

Fig. 2. Time to definite tube placement in seconds (s) using either a conventional endotracheal tube with a Macintosh laryngoscope (MAC) or the iGEL supraglottic airway in the different settings.

Fig. 3. Force (Newton, N) applied to the front teeth during intubation attempt using either a conventional endotracheal tube with a Macintosh laryngoscope (MAC) or the iGEL supraglottic airway in the different settings.

devices like LMA, LT-D, iGEL, Combitube, and EasyTube are fast, safe and easy-to-use [16]. The iGEL also provides benefits during ongoing CPR [11,17]. Intubation of trauma patients has always been a matter of discussion since with conventional ETI it is necessary to tilt the head slightly backwards, putting stress on a potentially injured spine. There- fore, the cervical spine of trauma patients is often immobilized, either by hand or by a specific device, e.g. a collar. Recent studies show that supraglottic airway devices improve success and Time to ventilation in such difficult access scenario [18], however, the choice of the optimum device for this purpose remained unclear [19]. We hereby could show that the iGEL supraglottic device is suitable for intubation of patients with immobilized spine and perform better that conventional ETI. This has not been shown before and is of impact for emergency services worldwide.

The iGEL performed better in all scenarios compared to ETI. Impor- tantly, the success rates differed largely when comparing the iGEL to ETI, with only 84% and 82% of participants being able to insert an ETT during immobilization correctly. This is a highly relevant finding since securing an airway is a keystone of emergency medicine and trauma pa- tients are a sensitive patient population. Success rates and TTI were slightly better during manual immobilization, but the difference was not significantly different. Of note, each participant was well-trained and skilled in ETI with several years of experience in emergency medi- cine. TTI was faster, although the mean time difference of a few seconds is not clinically relevant and may be attributed in part to the absence of a cuff on the iGEL which is consistent with a previous study in paramedic students [20].

Due to the fact that it is not necessary to use the modified Jackson position during insertion of the iGEL, head extension angle was much less in the iGEL scenario. That is of importance since further manipula- tion on an already injured spine may in this case cause irreparable harm to the patient [21]. These findings are in accordance with studies showing that iGEL is feasible for Emergency airway management in

Table 2

Scenario B: cervical manual in-line stabilization.

Parameters	MAC	iGEL	P-value
Time to intubation (s)	20 [18-22]	11.5 [11-13]	P b 0.001
Success of intubation n (%)	39 (84.8%)	46 (100%)	P = 0.006
Head extension angle	4 [3-5]	0 [0-1]	P b 0.001
Tooth compression [N]	27 [25-32]	16 [16-18]	P b 0.001
VAS score	4.5 [3-6]	2.5 [2-4]	P = 0.008

P. Gawlowski et al. / American Journal of Emergency Medicine 35 (2017) 484–487 487

Table 3

Scenario C: cervical immobilization using cervical extraction collar.

Parameters	MAC	iGEL	P-value
Time to intubation (s)	24 [21-27]	13 [11-14]	P b 0.001
Success of intubation n (%)	38 (82.6%)	46 (100%)	P = 0.003
Head extension angel	1 [1-2]	0 [0-0]	P b 0.001
Tooth compression [N]	32 [27-36]	17 [16-18]	P b 0.001
VAS score	6 [4.5-7]	2.5 [2-4.5]	P b 0.001

situations with reduced neck movement and limited mouth opening in post burn neck patients [22,23] [24], and it has been shown that effec- tive ventilation with the iGEL can be done with the head in different po- sitions, but head position has an impact on oropharyngeal leak pressure and cuff position [25], parameters we did not record in our study.

Another parameter that showed a benefit for the iGEL was force applied to the front teeth. The overall incidence of Dental injury in the literature is reported between 0.06% and 12% with the ETT [26-30]. The risk of dental injury is practically non-existing with iGEL insertion, as it is usually inserted without utilizing a laryngoscope. Therefore, inexperienced medical staff might benefit from using it for emergency airway management [16].

Last, participants rated the iGEL significantly better for use during both immobilization scenarios. Other studies also found that the iGel is preferred instead of an oropharyngeal airway and in some centers the device has become the supraglottic airway of choice during the ini- tial phase of CPR whilst the resuscitation team is summoned [12].

A limitation of our study and of most other studies in this field is the management of simulated airway situations in a manikin instead of real patients [31-36]. However, manikins allow for simulating the exact same airway situation for each participant and pose the only way to simulate standardized airway situations to date. Also, Cook et al. did not find any performance differences in four tested manikins [35]. How- ever, full-scale patient simulators are generally acceptably realistic but have significant limitations regarding the human airway anatomy and shortcomings with the manikin’s ability to replicate problems with lim- ited mobility of the cervical spine [37]. Further, the manikin’s anatomy may favor a specific model of airway device [33-35]. Since the specific manikin utilized in this study has not been previously tested in this re- gard as of yet, it remains unclear whether the anatomy of manikin fa- vors a distinct device.

1. Conclusions

Conclusively, we showed that blind intubation with the iGEL supraglottic airway was superior to ETI using the Macintosh laryngo- scope performed by paramedics in a simulated cervical immobilization scenario in a manikin in terms of success rate, time to definite tube placement, head extension angle, tooth compression, and rating.

Source of support

No sources of financial and material support to be declared.

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