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Simulated and protocolized rapid sequence intubation (RSI) in an AW169 is as quick as simulated “outdoor” RSI.
The time to secure endotracheal intubation (ETI) through an emergency front of neck access approach during a “can't intubate, can't ventilate” scenario did not differ between the “outdoor,” “aircraft,” and “helmets” scenario.
Perceived distractions to in-cabin RSI, such as the wearing of a flight helmet with simulated engine noise and radio transmissions, had no impact on the time to ETI.
Prehospital rapid sequence intubation (RSI) is an important aspect of prehospital care for helicopter emergency medical services (HEMS). This study examines the feasibility of in-aircraft (aircraft on the ground) RSI in different simulated settings.
Using an AW169 aircraft cabin simulator at Air Ambulance Kent Surrey Sussex, 3 clinical scenarios were devised. All required RSI in a “can intubate, can ventilate” (easy variant) and a “can't intubate, can't ventilate” scenario (difficult variant). Doctor-paramedic HEMS teams were video recorded, and elapsed times for prespecified end points were analyzed.
Endotracheal intubation (ETI) was achieved fastest outside the simulator for the easy variant (median = 231 seconds, interquartile range = 28 seconds). Time to ETI was not significantly longer for in-aircraft RSI compared with RSI outside the aircraft, both in the easy (p = .14) and difficult variant (p = .50). Wearing helmets with noise distraction did not impact the time to intubation when compared with standard in-aircraft RSI, both in the easy (p = .28) and difficult variant (p = .24).
In-aircraft, on-the-ground RSI had no significant impact on the time to successful completion of ETI. Future studies should prospectively examine in-cabin RSI and explore the possibilities of in-flight RSI in civilian HEMS services.
Prehospital emergency medical teams commonly perform advanced airway management in critically unwell patients.
Prehospital rapid sequence intubation (RSI) facilitates emergency endotracheal intubation (ETI). This is achieved by the administration of an induction agent followed by a rapidly acting neuromuscular blocking agent to induce unconsciousness and motor paralysis.
To achieve this, RSI usually must occur at the scene, which creates a delay in patient transfer to definitive in-hospital care. Performing RSI in the aircraft cabin has the potential to reduce time to definitive in-hospital care.
However, critically injured patients can have reduced conscious levels with deranged physiology, and in some cases prehospital RSI can be challenging and is not without risk. The rate of prehospital RSI complications
Commonly, it is undertaken with the patient on an ambulance trolley in an open area, allowing for 360-degree access. However, inclement environmental conditions, poor lighting, and scene hazards (including bystander interference) can create suboptimal conditions in which to perform an already challenging clinical intervention.
In the majority of cases, RSI is performed close to the scene before transferring the patient to a waiting ambulance or helicopter, which perhaps extends the prehospital time. Performing RSI in a helicopter cabin could protect the patient from inclement conditions and has the potential to reduce scene time
Principally, this reduces the time that the aircraft and its personnel spend on the ground under immediate threat from enemy action, while also reducing transfer time to definitive care. Military helicopters in this role often have cabins that allow for 360-degree access to the patient, with capacity for carrying the equipment and monitoring devices necessary for ensuring safe practice.
Unlike many former civilian aircraft types used in UK HEMS operations, the interior of Leonardo helicopters (AW169) allows the patient to be positioned centrally in the cabin with almost complete 360-degree access, as well as allowing greater working space in the cabin in general. This presents an opportunity to examine whether civilian HEMS practice could safely extend toward conducting RSI within the aircraft cabin.
In-aircraft RSI is not yet common in civilian prehospital care practice. The adoption of in-aircraft RSI could confer significant patient benefit but needs to be balanced against clinical risk and patient safety. The objective of this study was to examine the feasibility of on-the-ground, in-cabin RSI in an AW169 cabin in a simulated setting.
We designed a prospective simulation study. Three potential RSI environments were simulated in order to examine whether there was a significant difference between the time to complete RSI: scenario 1, “outside” of the aircraft; scenario 2, inside the “aircraft” cabin; and scenario 3, inside the aircraft cabin with simulated engine noise and radio transmissions (defined as “helmets”).
Each scenario was then performed in both “easy” (can intubate, can ventilate) and “difficult” (can't intubate, can't ventilate) variants wherein the difficult variant required the team to perform emergency front of neck access. Prespecified time points were recorded, and the primary end point was time to successful ETI in each of the scenarios.
Setting and Participants
This study was conducted in the high-fidelity simulation suite at the operational base of Air Ambulance Kent Surrey Sussex (AKSS) in 3 stages over a 6-month period. The simulation suite contains a replica AW169 simulator. The aircraft simulator comprises a bespoke modular in-cabin simulator and stretcher system, with 360-degree video capability and external capability to record both audio and visual input. As per AAKSS aviation protocols, helmets were worn (Alpha Eagles 400, MEL Aviation Ltd, UK) and connected to the intercom during the corresponding scenario, enabling direct communication with the primary investigator (A.M.).
Each scenario used a HEMS doctor (intubator) and HEMS paramedic (airway assistant) plus 2 ambulance clinicians, providing manual in-line stabilization (MILS) and cricoid pressure to mirror our conventional practice. During the in-aircraft with helmets scenarios, only 1 ambulance clinician was used; this clinician provided MILS when the patient was positioned in the cabin of the aircraft. After the procedure, this clinician removed themselves from the simulator.
HEMS doctors and paramedics were all regularly practicing personnel within our service with the prerequisite training and experience to provide this level of intervention. The doctor-paramedic team and the sequence of simulations were not randomized, and subjects voluntarily participated in 1 or more scenario. Each team member participated in each scenario only once.
Prespecified time points were collected using a GoPro video camera (series HERO 7; GoPro, San Mateo, CA). The start of the RSI checklist was defined as time “zero.” Other prespecified end points included the following: the end of the prehospital emergency anesthesia checklist, the decision to perform surgical airway (if required), an endotracheal tube (ETT) in the trachea, the bougie removed, the ETT cuff inflated, the bag valve mask connected, and an ETT placement check (with simulated chest rise/colorimetric end-tidal carbon dioxide change/misting of the ETT and the presence of an end-tidal carbon dioxide trace). A second investigator (J.G.) independently reviewed the video timings.
A full-body SimMan manikin (Laerdal Medical, Stavanger, Norway) was used. All “out-of-aircraft” scenarios were performed in an artificially lit environment with 360-degree patient access. A standard airway “kit dump” was prepared consisting of a 7-mm ETT with a gum elastic bougie (15CH), a Macintosh laryngoscope blade (size 4), a preassembled “circuit” consisting of a heat and moisture exchange filter, a catheter mount, and a sidestream end-tidal carbon dioxide sample line. Preassembled ventilator tubing enabled connection to the Oxylog 3000 plus (Draeger, Lübeck, Germany). This standardized equipment layout reduced interoperator variation.
As per AAKSS SOPs, the intubator was kneeling at the head end of the manikin, which was positioned on a stretcher with 360-degree access. The airway assistant knelt next to the intubator. Preoxygenation was simulated using a face mask and high flow oxygen. Simultaneously, the airway assistant established monitoring in compliance with AAKSS SOPs and the Association of Anaesthetists of Great Britain and Northern Ireland's recommendation.
A simulated TEMPUS Pro RDT monitor (Philips Healthcare, UK) was used. Before anesthesia, challenge and response checklists were completed. Subsequently, the RSI drugs were administered in immediate succession. Intubation was attempted using direct laryngoscopy and ETT placement verified.
In the aircraft scenarios (Figure 1, Figure 2), the intubator faced the rear of the aircraft positioned at the head end of the stretcher (seat 1C) and either sat or kneeled. The airway assistant was positioned kneeling, opposite the intubator and in front of seat 2A. A kit dump was laid out alongside predrawn drugs, and a Laerdal Compact Suction Unit (Laerdal Medical) was available (Supplemental Fig. S1). The ambulance clinician performed MILS while kneeling on the aircraft floor and facing the intubator. Once the airway and the head of the manikin were secure, if the intubator needed to reposition during the scenario, the ambulance clinician was predrilled to leave the aircraft cabin. During the difficult variant, the intubator was unable to pass the ETT, and a decision was made to proceed to emergency front of neck access as per AAKSS SOPs. During the helmets scenario, prerecorded air traffic control audio loops with background engine noise were played through the helmet to each participant at 25 dB.
Data Collection and End Points
Timings were documented by investigators (A.M./J.G.) from the video recordings of the procedure. The primary end point was the time to securing the ETT (seconds). The intubation time was defined as commencement of the checklist to when the ETT was secured. Successful ETI was defined as securing of the ETT with simulated confirmation end-tidal carbon dioxide capnography.
This study met National Institute for Health Research criteria (UK) for service evaluation. Internal approval by the AAKSS (Air Ambulance Kent Surrey and Sussex) Research Audit and Development Committee was gained. Written informed consent was gained by participants in the simulation study, with the option to withdraw at any stage. Participant information was anonymized and stored on electronic devices with technical encryption. The study was registered with the University of Surrey.
Descriptive statistics with frequencies, median, and associated interquartile ranges are reported. The Wilcoxon signed rank and Mann-Whitney U tests were used to assess the differences between each group for paired and unpaired data respectively, with P < .05 regarded as statistically significant. All analysis was completed using SPSS Version 26.0 (IBM Corp, Armonk, NY).
The descriptive statistics associated with time to successful ETI across the 6 different scenarios are reported in Table 1. The fastest time to successful ETI was found for the easy variant of the outside scenario (median = 231 seconds, interquartile range = 28 seconds), whereas the slowest median for successful ETI (median = 360 seconds, interquartile range = 41) was found for the difficult variant of the helmets scenario.
Table 1The Time to Endotracheal Intubation (ETI) for Each Scenario
In all 3 scenarios (outside, aircraft, and helmets), it took longer to secure the tube in the difficult variant compared with the easy variant (Table 2), reflecting the greater number of steps required in the “can't intubate, can't ventilate” scenario.
Table 2A Comparison of Scenarios With the Difference in Seconds and the Associated P Value
The difference in the median time to complete ETT was not significantly longer for the aircraft compared with the outside scenario, both in the easy variant (2 seconds, P = .138) and the hard variant (7 seconds, P = .500), implying that the work space in the cabin did not significantly affect the ease and speed of RSI.
Finally, to examine the effect of noise distraction and wearing an aircraft helmet on RSI performance, the helmet scenario was compared with the aircraft scenario. No significant difference was found between the easy aircraft versus the easy helmet scenarios (P = .282) or the difficult aircraft versus difficult helmet (P = .24) scenario. The airway was secured, either by intubation or completion of a surgical airway in all scenarios (100%).
In this study, we found that on-the-ground, in-aircraft RSI in a simulated AW169 cabin is feasible, and we feel that the simulation was of sufficient quality to infer that real-world feasibility also exists. Neither working space or noise distraction affected the time to successful endotracheal tube placement compared with the standard outside, 360-degree access approach.
RSI should be performed at the right time and in the right place when the environment and patient's physiology have been optimized as far as possible. In civilian HEMS practice, most enhanced care prehospital services advocate an outdoor location with 360-degree access to the patient.
analyzed HEMS ETI success for in-flight intubations, concluding that ETI was just as likely to be successful in-flight as in other circumstances. A 31-month retrospective review looked at all patients intubated preflight (249 patients) or en route (233 patients). The study reported a decreased scene time for those intubated en route (11 ± 6 minutes) versus those intubated at scene (16 ± 8 minutes), with success rates of 90% in-flight versus 92% on the ground.
reported a simulated study, akin to our study, of 14 prehospital physicians randomized to complete RSI either on an ambulance stretcher or inside an Airbus H145 cabin using an in-cabin protocol. They reported a 100% success rate on first attempt for in-cabin RSI, with a delay to establishing ETI by 63 seconds (P = .01). The authors concluded the overall scene time may be decreased with in-cabin RSI.
Compared with previous studies, in this study we examined systematically both potential physical boundaries for in-aircraft RSI and factors affecting cognitive capacity and situational awareness of the crews. We found that in-aircraft RSI did not significantly affect the time to correct ETT placement. Adding noise distraction (by wearing flight helmets and using an intercom system) increased the time to successful ETT placement slightly but not significantly. This is a promising first step to further investigate the feasibility and safety of in-cabin RSI in-flight (instead of on the ground) in an AW169 aircraft.
Furthermore, to the best of our knowledge, this is the first simulation study to investigate the feasibility of “can't intubate, can't ventilate” scenarios during RSI in an aircraft cabin. Although the time to ETI was longer compared with the “can intubate” scenario, the actual median difference was smaller for the in-aircraft compared with the outside scenario.
Our findings are of importance to HEMS teams using similar or comparable aircraft. AAKSS operates in a semirural area with long transport times to the hospital. We are often met by variable ambulance resources. The AW169 provides a familiar and constant environment compared with both the attending ambulance and the outdoors. In addition, transferring the patient from the ambulance straight to the aircraft for RSI arguably removes 1 step in the timeline, increasing temporal flow and reducing the overall time to hospital. In our trauma system, with a robust ambulance critical care service, we hypothesize that time savings could be made during night HEMS missions in which the aircraft is met by a land ambulance, either at an ad hoc or presurveyed landing site.
Our study has several limitations. First, the generalizability of our findings is limited. Other HEMS services have different SOPs, governance procedures, RSI protocols, and operational aircraft. Therefore, this simulation study cannot recommend general in-cabin RSI. The unique operational environment and patient need must be assessed by individual services, with careful and considered implementation. Second, this was a nonrandomized simulation study performed on manikins in a relatively unchallenged environment with a small number of participants. As reported by Kornhall et al,
the findings may not be translatable to real-world settings. For example, we do not fully assess the perceived complexities that may occur because of limited space in both the horizontal and vertical plane to the intubator.
Furthermore, there might have been a practice effect due to the study design being phased over several months. Because randomization was not performed, we cannot exclude that differences in experience between the various crews may have accounted for part of the findings or that learning and practice were playing a part. Finally, the time-consuming nature of the research resulted in a small number of comparisons, and, therefore, the power to detect any significant differences regarding timings was limited.
Further studies are warranted to investigate how we can further optimize the conditions and equipment for in-aircraft RSI. Prospective research is warranted to explore whether in-aircraft prehospital emergency anesthesia RSI could have a positive effect on patient outcome.
Simulated in-cabin RSI in a simulated AW169 is feasible and as quick as performing simulated RSI “outside.” Being in an aircraft cabin and wearing a flight helmet with background audio distraction did not have an impact on the time to intubation. Further research is warranted to explore the effects of in-aircraft RSI in real-world clinical settings and whether the potential for in-flight RSI might be of benefit to patient care.
The authors wish to thank all colleagues at Air Ambulance Kent Surrey Sussex for their participation and support of this study. The authors also wish to thank South East Coachworks (www.southeastcoachworks.com) for providing the bespoke helicopter simulator. We also thank the colleagues at Leonardo Helicopters, Specialist Aviation Services, and the University of Surrey for their contributions to this study.