The confined spaces and restricted access to patients in the urban search and rescue (USAR) environment dictate the need for a supraglottic airway device (SAD) which may be easily inserted, potentially single-handed, with only limited access to the patient's head. The laryngeal mask airway (LMA) has been widely used in the prehospital environment but requires inflation of the cuff, using two hands after insertion, before it can be effective. Given the specific features of the i-gelTM airway (Intersurgical Ltd, UK), it is possible that this device is more suited to this environment.
Chemical, biological, radiological and nuclear (CBRN) incidents are currently approached using a major incident management model. This assumes there are mass casualties and dictates that anyone who is not breathing spontaneously following appropriate airway manoeuvres is effectively dead (Advanced Life Support Group, 2002). Airway management in this environment, therefore, has never been an issue. It is possible that non-terrorist radiation or chemical incidents may involve only a small number of casualties and major incident standard practices would be inappropriate if used.
Paramedics in the hazardous area response team (HART) environment may be expected to perform airway manoeuvres that are technically difficult, if not impossible, while wearing personal protective equipment (PPE) required in a CBRN emergency. It is possible that the features of a supraglottic airway device such as the i-gel airway would allow easier insertion by an operator who is wearing PPE.
Studies in anaesthetized patients have demonstrated that i-gel airways are easily placed by non-specialist operators (Wharton et al, 2008). Recent publications have demonstrated the comparable efficacy of the i-gel airway with a laryngeal mask airway (LMA) in emergency situations (Theiler et al, 2009). However, there are currently no studies which examine the use of the i-gel airway in the prehospital setting, especially in the difficult access or limited dexterity environments encountered by HART paramedics.
Methods
Study objectives and design
This was an experimental study to:
Null hypotheses
For the purposes of this study, ‘normal’ conditions meant the mannequin lying supine on a patient trolley. The ‘confined space’ was simulated by placing the mannequin on the floor and separating the operator from the mannequin by a board with a 30 cm square hole cut in it and placed at the level of the mannequin's thorax (Figure 1), hence preventing direct access to the head. The HART PPE was standard issue gas-tight suits.
Sample size
The primary outcome for the comparison of the i-gel airway with a standard LMA under ‘normal’ conditions was time to achieve successful inflation of the mannequin's chest using a self-inflating bag-valve device. A sample size of at least 23 insertions per airway was required to detect a difference of 1.5 seconds between the two airways, with 80% power at a 5% level of significance.
This power calculation was based on the time to successful inflation using the LMA reported in a study by Ander et al (2004); median 6.9 seconds, 95% CI 5.5–8 seconds.
Ethics approval
Ethics approval was granted by the York Research Ethics Committee, part of the NHS National Research Ethics Service. The project received NHS permission from Harrogate and District NHS Foundation Trust and the Yorkshire Ambulance Service NHS Trust.
Participants
The operators who inserted the airways were either:
The results from the group of anaesthetists provided a context for the results from the paramedics. There was no intention to compare formally the performance of the anaesthetists and the paramedics.
Anaesthetists and paramedics who met the inclusion criteria were identified and sent an information leaflet about the study. Five anaesthetists and five paramedics took part in the study and gave written consent for their participation.
Training
Five anaesthetists and five USAR paramedics received training on insertion of the i-gel airway. The training was provided by the manufacturer of the i-gel airway—Intersurgical Ltd, UK. The one hour training session comprised:
Choice of mannequin
A mannequin was chosen instead of patients because of the ethical issues of inserting airways into patients in unusual environments. This is particularly relevant in this project where it is not known if it is possible to insert the i-gel airway in a USAR environment or when personnel are wearing PPE. Mannequins are used to teach medical skills that are not routine, especially those required in an emergency situation (Jordan et al, 2007).
Several studies have evaluated different mannequins as patient simulators for training in the insertion of supraglottic airway devices (Cook et al, 2007; Jackson and Cook, 2007). The authors concluded that the performance of mannequins varies with different airways, hence the selection of an appropriate mannequin is important.
The Laerdal® Airway Trainer (Laerdal, Norway) has been identified as one of two mannequins that are suitable for use with a wide variety of SADs (Jackson and Cook, 2007). The Laerdal® Advanced Life Support mannequin (Laerdal, Norway) was used for the study as it has similar oropharyngeal ‘anatomy’ to the Laerdal Airway Trainer and had the added benefit of having a ‘body’ to realistically obstruct the paramedics in the confined space scenario.
Airway
A size 4 i-gel airway or a standard size 4 LMA was used for all insertions. The size of LMA was identified in a previous study as the ‘best’ size for use in mannequins, including the Laerdal Airway Trainer (Cook et al, 2007). A size 4 i-gel airway was also the size of airway that Wharton et al (2008) reported using in their patients.
Procedure
Paramedics
Data collection took place at an ambulance service training centre. The paramedics performed five insertions of both SADs under 3 conditions:
Anaesthetists
Data collection took place in a theatre recovery room. The anaesthetists each performed five insertions of both SADs under ‘normal’ conditions (with the mannequin in a supine position on a patient trolley). In each condition some operators began with the i-gel airway and others with a standard LMA. Thereafter, the order of inserting the SADs was alternated.
Outcome measures
Data were summarized using descriptive statistics. The difference in insertion times between the i-gel airway and the standard LMA was analysed using a repeated measures ANOVA, to take into account multiple insertions by the same operators. A P-value of <0.05 was taken to indicate statistical significance. Data were entered onto a database in the statistical software package IBM® SPSS® held by York University.
Results
Normal conditions
There was no difference in the number of insertion attempts to inflate successfully the mannequin's chest using the i-gel airway compared with the standard LMA. Forty nine of the 50 insertions of the LMA were successful at first attempt, one at second attempt. All 50 insertions of the i-gel were successful at first attempt.
The mean insertion times were faster for the i-gel than the standard LMA (Table 1). Twenty-three of the 25 insertions performed by the paramedics and 22 of the 25 insertions performed by the anaesthetists were faster for the i-gel.
| i-gel | LMA | Difference in means | |||
|---|---|---|---|---|---|
| Mean (SD) seconds | Mean (SD) seconds | Mean (SD) seconds | 95% CIs | ||
| 5 Anaesthetists (25 insertions) | 16.28 (3.64) | 25.64 (12.18) | 9.36 (11.72) | 4.25 to 14.47 | P=0.04 |
| 5 Paramedics (25 insertions) | 21.36 (7.88) | 29.04 (10.27) | 7.68 (4.99) | 2.47 to 12.89 | P=0.42 |
When we adjusted for multiple insertions by the same operator, and also for occupation, there was a statistically significant difference between the insertion times for the i-gel compared to the LMA for the anaesthetists (P=0.04), but not for the paramedics, P=0.42 (Table 1).
Simulated USAR environment
In the simulated USAR (confined space) environment there was no difference in the number of insertion attempts to successfully inflate the mannequin's chest using the i-gel airway compared with the LMA. All 25 insertions of the LMA were successful at first attempt as were those for the i-gel airway.
The mean times for insertion were faster for the i-gel than for the standard LMA (Table 2) and all 25 insertions of the i-gel were performed more quickly than with the LMA.
| i-gel | LMA | Difference in means | |||
|---|---|---|---|---|---|
| Mean (SD) seconds | Mean (SD) seconds | Mean (SD) seconds | 95% CIs | ||
| 5 Paramedics (25 insertions) | 24.48 (6.95) | 38.36 (14.81) | 13.88 (10.06) | 7.30 to 20.46 | P=0.001 |
When we adjusted for multiple insertions by the same operator, there was a statistically significant difference between the insertion times for the i-gel compared to the LMA, P=0.001 (Table 2).
Wearing CBRN PPE
When wearing CBRN PPE, there was no difference in the number of insertion attempts to successfully inflate the mannequin's chest using the i-gel airway compared with the LMA. All 25 insertions of the LMA were successful at first attempt as were those for the i-gel.
When wearing PPE, the mean times for insertion were faster for the i-gel than the standard LMA (Table 3) and 24 of the 25 insertions were performed more quickly using the i-gel airway. However when we adjusted for multiple insertions by the same operator, the difference between the insertion times for the i-gel compared to the LMA was not statistically significant, P=0.11 (Table 3).
| i-gel | LMA | Difference in means | |||
|---|---|---|---|---|---|
| Mean (SD) seconds | Mean (SD) seconds | Mean (SD) seconds | 95% CIs | ||
| 5 Paramedics (25 insertions) | 27.24 (7.93) | 38.28 (11.21) | 11.04 (9.52) | 5.52 to 16.56 | P=0.11 |
In all situations, the operators reported that insertion of both supraglottic airway devices were ‘easy’ using the four-point Likert scale. However, they also consistently reported that insertion of the i-gel was easier than the LMA.
Discussion
The results of this study show that, while insertion of both LMA and i-gel supraglottic airway devices are possible in a variety of prehospital settings, the use of i-gel airways is subjectively easier. This is most probably due to the need to attach a syringe and inflate a cuff with the LMA, a step which is absent with the i-gel. The absence of this step becomes more pronounced in situations where manual dexterity and/or access to the patient is compromised and may become clinically significant in these situations. However, it was only possible to demonstrate statistical significance in situations where access was compromised.
The paramedics had no difficulties in using the i-gel during the study, demonstrating that extensive familiarization before clinical use is not necessary for those already familiar with using SADs in the prehospital setting.
The i-gel supraglottic airway device is the latest addition to the increasing number of supraglottic airway devices available in the UK. Interest has been shown in its possible application outside of anaesthesia for elective surgery, due to its simplicity of insertion and subsequent stability, particularly in the area of resuscitation (Soar, 2007).
In view of the recent JRCALC publication on prehospital airway management (JRCALC, 2008), it is an appropriate time to investigate the potential use of the i-gel device in the varied prehospital environments.
Study limitations
The use of simulators can never completely replicate the clinical environment. However, the authors believe that careful selection of the type of mannequin used in the study has provided a means of reliably comparing the two SADs under investigation.
A Laerdal ALS mannequin was not available when data was collected from the anaesthetists. A Laerdal Airway Trainer was used, which shares similar oropharyngeal anatomy to the Laerdal ALS mannequin and, as the study was not comparing anaesthetist with paramedic practice, no detriment to the quality of the study was identified.
Time-to-successful-outcome measure of mannequin chest rise was measured using a stopwatch controlled by a Rescucitation Council (UK) ALS instructor. A potentially more sophisticated means of recording the time taken from the start point of opening the packet containing the SAD to successful chest rise may have employed video-recording timelines. However, the authors do not believe that this would have significantly altered the outcome of the study as human interpretation of the video recording would still be required.
Conclusion
This study has demonstrated that, in simulated prehospital settings, the i-gel supraglottic airway device performs at least as well as the LMA and is significantly quicker to insert in some situations. The authors therefore recommend that the i-gel is introduced into the USAR HART environment with further clinical evaluation in prehospital settings.