Videolaringoscopy Beyond Conventional Endotracheal Intubation in HEMS: A Real Flight Simulation

Background : In pre-hospital setting, airway management may be required during hems transportation, when patients deteriorate while en route. Our primary objective was to assess whether in-flight indirect laryngoscopy in frontal right-lateral sitting position (FP) of the operator, is such effective as traditional indirect laryngoscopy methods onshore, considering, also, the association of success rate with influencing flight factors (flying, devices, position, comfort VAS, Lumen VAS). Methods : This observational prospective study, aimed to estimate the success rate of in-flight FP indirect laryngoscopy intubation. The study conducted on an AW 169 helicopter (©Leonardo Company, Italy) equipped with transversal stretcher, during steady flight. Indirect laryngoscopy devices (GlideScope Ranger and AirTraq) were used on a HAL® manikin (Accurate, Gaumard® Scientific Company,Inc) with cervical collar. Results : All of the FP intubations with both devices were successful after two attempts maximum. The mean time for intubation was slightly greater using the Glide Scope Ranger (mean 45.4±32.2 ”) compared to AirTraq (mean 34.8±26.7 ”). Conclusions : Both AirTraq and GlideScope Ranger used in in-flight FP guarantee a comparable level of effectiveness to traditional onshore method with 100% successful rate of intubation, Airtraq seems not been affected by Lumen, indicating that in this specific contest it guarantees a high visualisation regardless the light conditions. On the other hand, the FP results effective using AirTraq in both conditions.


Background
Critically ill or injured patients need to be immediately identified, properly managed and rapidly transported to definitive care. According to the algorithm of Pre-hospital Trauma Life Support, the A-B-C-D-E approach is fundamental during patient's assessment [1].
All patients undergoing medical evacuation by helicopter may require, in the meanwhile, emergent intubation. Improved training and expertise have enabled emergency medical personnel to provide advanced levels of care at the scene of trauma. Advanced techniques, in the hostile environment or whenever transport times are prolonged, should be guaranteed both, on field and in the helicopter, in order to assure a favourable outcome.
Successful emergency airway management is an essential component of the modern practice of rescue medicine and it has guaranteed during both day and night missions.
Airway management may be required during medical evacuation in a helicopter when patients deteriorate en-route. Direct laryngoscopy can be challenging, even for welltrained, experienced personnel. The repercussions for unsuccessful or prolonged attempts at intubation can be dramatic, in case of difficult airways, are not limited to the operating room context but can be also apply to the pre-hospital setting of helicopter emergency medical service (HEMS) [2]. In addition, laryngoscopes positioning at the head of the patient during in-cabin manoeuvres may not be always possible, making it difficult to perform traditional, direct laryngoscopy.
In the last years, the use of a video laryngoscope as the primary method of intubation has been shown in many cases to be at least as good as, and often more successful than, direct laryngoscopy [3].
Owing to the development of medical technology, there are an increasing number of video laryngoscopes and other devices facilitating endotracheal intubation in several airway scenarios. Each of these devices may bring benefits by increasing the in-flight intubation effectiveness, as well as shortening the procedure, provided that, the healthcare personnel performing intubation is familiar with the use of the device.
Most intubations by HEMS crews occur before loading the patient into the helicopter.
However, some in-flight intubations are necessary owing to unforeseen circumstances, such as patient deterioration in-flight or accidental dislodgement of an endotracheal tube.
Should an in-flight intubation be necessary, direct laryngoscopy becomes more difficult by space and mobility limitations. Simply put, in the cramped quarters of a helicopter, it can be difficult to obtain the proper line of sight needed to right place the endotracheal tube using direct laryngoscopy [4].
While the skill of tracheal intubation via direct laryngoscopy taught to many healthcare professionals, it is a difficult skill to acquire and maintain [5]. Serious consequences may result from a poorly performed intubation attempt. The rate of airway-related complications correlates with an increased number of intubation attempts. The increased number of laryngoscopy attempts increases the incidence of hypoxemia, aspiration, bradycardia, and cardiac arrest [6] (Thus, successful intubation occurring on the initial attempt is imperative. Several studies compared direct laryngoscopy using a Macintosh blade with Videoassisted intubation devices and found a more rapid acquisition of skills and faster and more consistent intubation in difficult scenarios and less theoretical dental trauma (in intubations performed on a manikin) [7][8][9]5].
First-time users of video assisted intubation devices have an improved view of the glottis during difficult airway situations compared to direct laryngoscopy [10]. The skill of novice laryngoscopists diminishes rapidly over a period of several months without intervening practice [11]. Alternatively, a laryngoscopy approach is available to perform endotracheal intubation from a ventral position while directly facing the victim. This technique repeatedly reported, but systematic data on the usefulness of this approach are scarce.
In recent years, alternative intubation techniques, including indirect optical laryngoscopy and video laryngoscopy, increasingly used to facilitate tracheal intubation [12]. Because of this, such techniques may also be useful in the context of face-to-face intubations. This research is focused on proving that in-flight, in-cabin, indirect laryngoscopy by AIRTRAQ™ or GLIDESCOPE ® RANGER in frontal-right-lateral position, is able to guarantee airway management.

Materials and Methods
We designed this observational study in prospectively collected data, comparing No specific performed training on the devices prior to use in the study. Therefore, participants may have used a different device at their home hospital. Lumen measurements taken at distance of 20 cms, on the left side of the mannequin. All phases of the experiment registered by full-hd camera in order to evaluate and discuss collected data after the debriefing.

Statistical analysis
Success rate was the primary outcome on which sample size has calculated. A previous study reported a success rate of 88% for inverse intubation of the manikin with Airtraq® [13].
We consider and presume that a useful alternative technique should have a success rate of more than 90% (ideally approaching 100%). Hence, we powered our study to detect a clinically meaningful difference in success rate of more than 15%. With a targeted power of 80% and a two-tailed α level of 0.05; this requires a sample size of 20 per group.
The primary endpoint was successful establishment of endotracheal airway intubation.
Normal distribution of linear data has been proven by Kolmogorov-Smirnov. Mann-Whitney U test (two-tailed), Q-square test, T-test and were used to detect significant differences among groups investigating as appropriate.
The association of success rate with influencing factors (flying, devices, position, comfort VAS, Lumen VAS) was assessed using Logistic Regression Analysis and Pearson correlation.
Linear regression analysis has been used for evaluating the association of intubation success rate with potential influencing factors. A p-value of 0.05 (p<0.05 was considered statistically significant) was deemed to be statistically significant throughout the study.

Success Rate
Successful intubation, at the first attempt obtained in 114 cases (95%) while in 5% at the second attempt.
There is no significant difference in the success rate of intubation between the devices (AT

Endotracheal tube insertion time
The comparison of the required time for successful intubation between the devices,

Subjective comfort rating and Lumen class
Regarding the difference in Comfort VAS score, expressed as a categorical scale from 1 to 10, by the operator, the comparison showed a statistical significance, with better comfort VAS expressed when intubating with Airtraq (AT Group n=60 mean 1.75±0.9, median 2 vs GSR Group n=60, mean 4.5±2.6, median 4; p=0.00001).
Similarly, during inflight simulation in frontal-right-lateral position the best comfort has been expressed when using the Airtraq (p=0.001).
The Lumen Class difference during the manoeuvres with both devices is not statistically significant (p=0.799), creating this way homogeneous conditions that permit to obtain a reliable comparison between the devices.

Linear regression analysis and correlation indicates how the intubation success rate is
influenced by the ambient conditions of luminosity (lumen class) (p=0.018), the success at the first attempt and the perception of well-being of the operator expressed through comfort VAS (p=0.0001) indicates how in general ambient light seems to affect the maneuver.

Discussion
Intubation of the normal airway in a well-lit environment may be challenging for the As we described, endotracheal intubation may occur during Helicopter Emergency Medical Service [15]. This can especially be challenging with entrapped casualties when access to the patient is restricted. In such situations, prehospital emergency personnel will usually administer oxygen and keep the airway open using basic airway techniques or supraglottic airway devices until the patient has been extricated [16].
However, if rapid extrication is not possible and when life-threatening airway obstruction and severe hypoxia persist, the advanced life support (ALS) provider may-in rare instances-be forced to attempt securing the airway with an endotracheal tube while the patient is still entrapped. Herein, conventional laryngoscopy is often not possible due to limited access to the head, and some ALS providers advocate the use of a primary surgical technique under such circumstances. Alternatively, a laryngoscopic approach is available to perform endotracheal intubation from a ventral position ("sitting" patient position) while directly facing the victim. This technique has repeatedly been reported, but systematic data on the usefulness of this approach are scarce, especially in a confined environment such as the cabin of an air ambulance [17][18]13].

Success Rate
In an environment, such confined as a helicopter, the videolaryngoscopy advantage of not requiring line-of-sight to intubate, might make intubation possible where it would have been impossible using direct laryngoscopy. Video laryngoscopes were developed to provide improved visualization and might help in these situations. Videolaryngoscopy also provides an added benefit of providing a method for quality improvement on intubation methods and performance that direct laryngoscopy cannot provide [19].
Brown et al. retrospectively reviewed intubation success rates from an 89 rotorcraft air medical system from January 1, 2007, through December 31, 2009 and concluded that the Airtraq device achieves success rates better than or at least comparable with other air medical direct laryngoscopy success rates when using mannequin [20].
Our study clearly demonstrates that there is a 100% successful intubation with both devices.
Success Rate was not influence by the kind of the device, the position and the inflight or onshore condition. Kronhall et al. in their study, registered a 100% in-cabin intubation success rate, too, in combination with how participants found in-cabin intubation conditions equal to or better than standard conditions [15]. This means that now and on, the scientific and the emergency medicine world should consider seriously indirect video-laryngoscopy as a valid concept to face since the first attempt, airway management en-route. Wider use of videolaryngoscopes in HEMS would increase the number of first-attempt successful endotracheal intubation in difficult airway scenarios.

Endotracheal tube insertion time
The expectation of modern HEMS was to perform advanced measures, including intubation without unnecessarily delaying hospital intervention. With our study, adequate time of inflight right-lateral-frontal successful intubation it was demonstrated, with a slightly higher performance in terms of time obtained by Airtraq than Glidescope Ranger. An absolute record time of successful frontal intubation (11''39 seconds) was register by using Airtraq. Prolonged scene times may increase mortality in certain critical injuries and illnesses because it delays hospital treatment [21][22]. With specialist HEMS, the benefits of early intervention are thought to outweigh the detrimental effects of prolonged scene times [23][24].

Subjective Comfort VAS rating and Lumen Class
The Lumen Class homogeneity resulted by the accurate lumen registration during our study, permitted a reliable interpretation of collected data, for what concerns both devices' efficacy.
Light emission is a remarkable concern when in-flight intubation, is operated during several favourable or forbidding conditions. Wallace et al. analysed light emission during endotracheal intubation in a high-fidelity patient simulator lab [25]. Even if in this study, light emission evaluation focused in avoiding ground-based observer to localize the aircraft in combat zones and avoid fire; our investigation is the unique underling efficient performance of endotracheal intubation associated to light emission.
Regarding our study, even both devices have a 100% successful rate of intubation, Airtraq seems not to be affect by Lumen, indicating that in this specific contest it guarantees a high visualisation regardless the light conditions.
Our findings suggest that in-cabin; en-route intubation can be performed, bypassing actual problems like space, stretcher position, and medical doctor seat thanks to videolaryngoscopic vision.
Use of video-laryngoscopy in prehospital settings will increase as within the next years, a further development of video-laryngoscopy is expected. We believe that video-laryngoscopy may facilitate practical execution of in-flight intubation guaranteeing a more optimal airway management under challenging conditions in an aeromedical aircraft. We are hopeful that further investigation of in-flight video-laryngoscopy, advances in technology and development of video-laryngoscopy management protocols will improve management of patient requiring intubation in helicopters.

Study limitations
As a pilot study, our experimentation remains a simulated intubation on a manikin with specific intubation parameters.

Conclusions
There are definitively few studies in literature, considering in-cabin intubation performed by physicians working in civilian prehospital care. Similar in-cabin (but not in-flight) intubation data have been previously documented only in a military context, but, on much larger helicopters as a means of facilitating rapid evacuation under fire and as retrospectively collected data.
Our findings reproduced, in an operational environment, in a steady flight, including this way potential critical environment conditions such as vibration, movement, noise and light exposure during the flight. This created a reliable simulation of in-flight intubation able to represent real conditions during the experimentation.
Nowadays it remains a unique in-cabin, in-flight study performed en-route and this definitively determines both the novelty idea and realization. We surely believe that innovation and practical investment in scientific research is the first path for results that could determine future medical management in HEMS.

Ethics approval and consent to participate
The University of L'Aquila Local Review Board reviewed this study and classified it as exempt from full review because it did not meet its requirements for research involving human subjects as it was executed on a mannequin.

Consent for publication
Consent for publication of photos/videos was obtained from both the official photographer Mr.
Pierluigi Facchetti and the official video reporter Mr. Diodato Salvatore. They both understood that the text and any pictures or videos eventually published in the article will be freely available on the internet and may be seen by the general public. The pictures, videos and text may also appear on other websites or in print, may be translated into other languages or used for commercial purposes. They have both been offered the opportunity to read the manuscript

Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests
The Authors declare that they have no competing interests. The Authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript.