This study comprehensively examines different LSI timings, expanding beyond previous literature primarily focused on single LSIs [8, 10]. Nearly all LSIs were completed within two minutes, except for RSI, which had a median duration of just under six minutes. Differences in TI across PHCP qualifications were minimal, however, PHCPs generally overestimated TIs with significant discrepancies observed in i-gel, finger thoracostomy, cricothyroidotomy, and needle decompression. In team-based LSIs, captured step durations increased steadily, with RSI preparation being the longest phase. Additionally, notable delays were observed in securing procedures, particularly for RSI and chest tube insertion.

Our findings show that interventions like oral fentanyl, OPA, oxygen delivery, and i-gel can be performed in similar or significantly less time compared to triage LSIs [5]. Integrating these faster interventions into triage protocols could reduce on-scene mortality and ensure timely critical care. OTFC emerged the fastest intervention in our study and has recently been adopted into civilian pre-hospital settings from military practices [10]. Given its rapid application, OTFC utilized to meet the need for rapid intervention and prevent care gaps in MCIs [10]; however, its adoption remains limited to specific regions, with London's Air Ambulance among the few implement it. Similarly, OPA and i-gel, which are both quick to perform and have high success rates, could be feasible for bystander use in MCIs [13]. The i-gel has the fastest insertion timings among airway devices, even when used with chemical, biological, radiological, and nuclear (CBRN) protective equipment, which supports its use in high-stress, resource-limited settings [14]. Similarly, other rapid LSIs, such as OTFC or OPA, could be integrated into initial response algorithms or tiered approaches to enable timely care by a wider range of responders and reduce scene delays.

RSI had the longest TI, taking 218 s longer than the chest tube, the second-longest procedure. Southard et al. reported a longer RSI time of 479 s—131 s more than our study’s median of 348 s—likely due to differences in measurement criteria [15]. Southard et al. define TI from the moment the flight crew crossed the ambulance threshold until the patient was declared transport-ready, whereas we recorded from equipment pickup or initial mannequin contact until airway security was achieved. Vincent-Lambert et al. reported a median RSI time of 14 min and 2 s; however, this included post-induction sedation and was performed by pre-hospital care students [16]. Nevertheless, RSI is rarely performed in MCIs due to its complexity, which strains limited resources by requiring advanced and multiple PHCPs as well as specialized equipment [17, 18]. Additionally, RSI requires continued airway management, which is challenging when triage is ongoing, and other patients need immediate care. Therefore, this substantial time and resource investment underlines the need for MCI pre-hospital care protocols to carefully evaluate the threshold for performing RSI. Strategies to reduce unnecessary delays may include standardized equipment kits with pre-packed components and pre-assigned team roles.

PHCPs must fully assess the time required to perform LSIs, carefully weighing the risks, benefits, and the urgent need for such interventions. Maintaining situational awareness enhances time perception, reducing delays and improving outcomes [19]. However, estimating LSI TIs remains challenging due to the unpredictable pre-hospital environment. Overestimation of LSI TIs may be attributed to the stress and high-pressure MCI environment in which they operate, known as distortion of time [19]. Studies have shown that during high-arousal or life-threatening situations, such as MCIs, individuals often perceive time as slowing down [19, 20]. Consequently, PHCPs in this study may have believed interventions take longer than they actually did due to this altered perception of time. This discrepancy highlights the value of immersive training environments that mimic MCI-related stress, which could help PHCPs to calibrate their time perception and improve decision-making under pressure [21].

Advanced invasive LSIs consume valuable resources and can delay on-scene time, potentially worsening patient outcome [22]. This study found RSI had prolonged preparation phases 58.8% of TI, lasting longer than the actual tube insertion itself. While preparation is necessary, optimizing certain aspects could reduce delays. Vincent-Lambert et al. similarly reported significant preparation time, though direct comparisons are limited by differing phase definitions [16]. We defined the preparation phase as the period before the syringe’s bolus push, aligning with findings from previous studies where preparation and pre-oxygenation constituted a major proportion of TI, highlighting the time-intensive nature of these early stages [16]. The securing phase also showed delays, particularly in RSI and chest tube procedures. Chest tube suturing had a median time of 58 s, shorter than the 96.3 ± 29.0 s reported by Mckee et al. but still identifying areas of delay [23]. RSI tube-securing delays may stem from the standard use of tube ties, suggesting that transitioning to tube holders could reduce TI [24]. To incorporate advanced LSIs into future MCI protocols, efforts should focus on minimizing unnecessary preparation and post-placement delays.

This study has several limitations. The main limitation is that the study was conducted in a simulated environment, devoid of real-world distractions, consequences, or risks. Despite the use of advanced simulation equipment, the setting may not fully replicate the complexity, unpredictability, and immediacy of large-scale real-life emergency incidents. Furthermore, real-world emergencies present unpredictable variables, including patient characteristics geographical location or incident type, which can influence the timing and feasibility of interventions. Secondly, despite efforts to standardize interventions, the complexity of advanced LSIs across different crews challenges the replication of identical timing trajectories, contributing to observed discrepancies in captured time points. Finally, the convenience sample, limited to available PHCPs, may restrict generalizability. A larger sample would likely offer a more representative overview of clinician experiences.