{"paper_id":"1a2adb64-a5b2-481f-971f-1633029096eb","body_text":"Quality of prehospital emergency care at high altitude: a randomized assessor-blinded simulation crossover study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Quality of prehospital emergency care at high altitude: a randomized assessor-blinded simulation crossover study Sven Straumann, Thomas Heidt, Fiona Uhor, Fabienne Frickmann, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9268709/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Background: High-altitude rescue operations expose Emergency Medical Services (EMS) teams to hypobaric hypoxia, which may impair cognition and team performance. However, its effect on the overall quality of prehospital emergency care remains unclear. We aimed to assess whether acute exposure to high altitude (3,450 m) is associated with reduced quality of simulated prehospital emergency medical care delivered by non-acclimatized EMS physicians. Methods : We conducted an assessor-blinded, randomized crossover simulation study in Switzerland between September 2024 and January 2025, in which 20 non-acclimatized EMS physicians managed simulated emergency scenarios under four conditions in randomized order: baseline at low altitude (540 m), acute exposure to high altitude (3,450 m), acute exposure to 3,450 m with supplemental oxygen at 4 L/min, and after 20 hours at 3,450 m. Video-recorded performances were independently assessed by three blinded experts using validated instruments for medical and non-technical performance. The primary outcome was a composite score comprising 50% medical and 50% non-technical skills. Seventeen participants completed all four scenarios and were included in the primary analysis. Results: Median [IQR] composite performance was 82% [76–83] at baseline, 74% [70–83] during acute exposure to 3,450 m, 82% [68–83] with supplemental oxygen, and 83% [77–86] after 20 hours at altitude. In generalized linear mixed modelling, overall composite performance did not differ significantly across the four conditions (P=0.082). Performance during acute altitude exposure (C2) did not differ significantly from baseline (C1) (-1%, 95% CI -5% to 3%; P=0.53). Supplemental oxygen (C3) did not improve performance compared with C2 (0%, 95% CI -4% to 4%; P=0.94), whereas performance after 20 hours at altitude (C4) was higher than at C2 (5%, 95% CI 1% to 9%; P=0.03). In exploratory adjusted analyses, greater prehospital experience was associated with better performance during acute altitude exposure. Conclusions: In this assessor-blinded simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in overall simulated prehospital emergency care among non-acclimatized EMS physicians. However, the confidence intervals do not exclude small clinically relevant decrements. Supplemental oxygen did not improve overall performance under these study conditions. Trial registration : ClinicalTrials.gov NCT06446427 High altitude hypobaric hypoxia prehospital emergency care emergency medical services (EMS) supplemental oxygen medical performance Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Background High-quality prehospital emergency medical care by expert teams improves patient survival and outcomes at hospital discharge.[1-4] Maintaining a high standard of prehospital care is therefore essential even under the demanding conditions of high-altitude rescue. However, high-altitude environments pose unique challenges that may limit the quality of medical care.[5-7] The defining feature of the environment at high altitude is the nonlinear decrease in barometric pressure, which leads to a reduction in the partial pressure of oxygen (pO 2 ) at every point along the oxygen transport chain, i.e. from the lungs to the mitochondria. If the body’s adaptive mechanisms fail to compensate for the lack of oxygen, symptoms of acute mountain sickness (AMS) may follow: headache, nausea, vomiting, fatigue, weakness, and dizziness/light-headedness.[8] In addition, hypobaric hypoxia can also impair higher cognitive functions, though the lowest altitude at which this becomes evident is subject to a considerable interindividual and activity-related variability.[9,10] If impairments arise, serious and even fatal errors may follow.[11] To date, research on the effects of acute high-altitude exposure on the quality of prehospital emergency medical care has focused primarily on the quality of cardiopulmonary resuscitation (CPR). Findings suggest that the quality of chest compressions declines[12-14], and rescuer fatigue occurs faster.[15-19] However, high-quality mountain rescue requires far more than adequate CPR; it demands complex medical, technical, and cognitive skills—all of which may be impaired at high altitude, potentially compromising treatment quality. Objectives The primary objective of this study was to assess whether acute high-altitude exposure (3,450 m) is associated with reduced quality of prehospital emergency medical care provided by non-acclimatized Emergency Medical Services (EMS) physicians during short, controlled, high-fidelity simulated emergency scenarios, compared with low altitude (540 m). Secondary analyses explored whether medical performance at high altitude was influenced by supplemental oxygen or a one-night stay at this altitude, and whether it was associated with years of prehospital experience, AMS severity, sex, or cognitive function. Methods Ethics approval Ethical approval for this study was provided by the Cantonal Research Ethics Committee Bern , Switzerland (Chairperson Prof. Christian Seiler) on 8 July 2024 (ID: 2024-00237). Written informed consent was obtained from all participants, and all study procedures were in accordance with the Declaration of Helsinki. Trial registration The trial was registered prior to the start of enrolment at ClinicalTrials.gov (NCT06446427, registration date: 6 June 2024) Study design The study followed a randomized crossover design. Participants We enrolled 20 EMS physicians (10 female). Inclusion criteria were: ≥2 years of training in anaesthesiology Certified prehospital Emergency Medical Services (EMS) physician ≥3 months of full-time prehospital work Medical team leader in ≥50 life-threatening prehospital cases (National Advisory Committee for Aeronautics (NACA) score≥4) Exclusion criteria were: Any medical condition known to place the participant at higher risk for hypoxia-induced adverse events (cardiovascular, pulmonary, neurological, otherwise) Travel to ≥2500 m within 4 weeks before the study (pre-acclimatization) Participants were recruited by announcements in online and print media (between 8 July 2024 and 14 August 2024). EMS physicians were chosen because they form the clinical core of physician-staffed medical emergency teams across Europe and are routinely responsible for advanced medical decision-making in high-altitude rescue. Setting The study was conducted between September 2024 and January 2025. The participants completed four simulated medical scenarios: one at the University Hospital Bern, Switzerland (540 m) and three at the High-altitude Research Station Jungfraujoch, Switzerland (3,450 m). The ascent to the research station was a standardized passive transport by train and gondola over 45 minutes, starting at 937 m. Participants were not allowed to use medication known to ameliorate AMS symptoms, such as acetazolamide or ibuprofen.[20,21] Participants were allowed to use the time between scenarios at leisure, but were not allowed any physically strenuous activities or the consumption of alcohol. The specific conditions (C1-C4) under which the participants completed the simulated scenarios are outlined in Table 1. The order of the scenarios was randomized from a balanced subset of 20 of all possible 24 permutations, such that each scenario occurred equally often under each condition across participants. This was done to eliminate order effects in case any scenarios were felt to be more difficult than others. Condition Condition code Altitude above sea level Location Time at high-altitude before scenario Gas administered via nasal cannula (4 L/min) Baseline C1 540 m Bern, Switzerland Not applicable Placebo (pressurized air) Acute high-altitude exposure C2 3,450 m Jungfraujoch Research Station 0.5 h Placebo (pressurized air) Supplemental oxygen C3 3,450 m Jungfraujoch Research Station 4 h 100% Oxygen After 20 h at high altitude C4 3,450 m Jungfraujoch Research Station 20 h Placebo (pressurized air) Table 1: Study conditions Conditions (C1 to C4) under which the simulated emergency scenarios were performed. Intervention The following four high-fidelity emergency medical scenarios were designed: Polytrauma with tension pneumothorax and open ankle fracture Myocardial infarction in an elderly patient, presenting with atypical symptoms (abdominal discomfort) and progressing to cardiac arrest Recurrent epileptic seizures and respiratory failure in a five-month-old baby with meningitis and pulmonary aspiration, mother present on scene Severe accidental hypothermia with unstable bradyarrhythmia, progressing to ventricular fibrillation due to rescue collapse Patients were played by two medical students, procedures (such as CPR, tracheal intubation, or chest tubes) were performed on mannequins, and clinical findings were shown via audio, video, or images (e.g., injuries, ECGs, breathing sounds). Participants had a full set of real equipment at their disposal and could delegate tasks to an assisting paramedic in each case. The role of the paramedic was filled by an experienced EMS physician. Participants were allowed to use supporting aids (e.g., paediatric dose sheets or calculators) consistent with real-life clinical practice. Participants had no prior knowledge about the nature of the scenarios and were not allowed to share information with other participants. Each simulated scenario lasted about 20 min, took place in a controlled indoor environment, and was video recorded for later analyses. Participants wore nasal cannulas in all conditions, but supplemental oxygen (4 L/min) was delivered only in C3. In the other three conditions (C1, C2, C4), identical flow rates of pressurized air (21% O 2 ) were used as placebo. Measurements Video recordings of all simulated scenarios were rated independently by three blinded outcome assessors (board-certified anaesthesiologists, experienced in both prehospital emergency medicine and simulation training). This video-based rating allowed for repeated, independent assessments and blinding, as widely recommended in recent literature.[22,23] To ensure assessor blinding to scenario location (low vs. high altitude), an identical setup and backdrop were used for all video recordings. Using validated scoring tools (Table 2), the assessors evaluated medical, communication, and leadership skills. Their independent ratings were averaged for analysis. The primary outcome was the overall performance, defined as a weighted composite score consisting of 50% medical skills and 50% non-technical skills (communication and leadership). Equal weighting was chosen a priori to reflect the established importance of non-technical skills, such as leadership and communication, for safe and effective prehospital emergency care, particularly in complex team-based scenarios.[24] See Supplemental Digital Content 1 for the detailed scoring matrix used to evaluate each scenario. Type of assessment Tool Score description References / Validation Approximate baseline performance reported in the literature Medical skills Modified Simulation Team Assessment Tool (STAT) Assesses scenario-specific medical actions required for adequate patient care using a 3-point Likert scale Reid et al. (2012) [27] 84% Non-technical skills Concise Assessment of Leader Management (CALM) Assesses leadership, communication, and crisis resource management using 15 items on a 4-point Likert scale Nadkarni et al. (2018), Florez et al. (2023) [28,29] 60% Non-technical skills Team Emergency Assessment Measure (TEAM) Assesses teamwork, task management, and crisis resource management using 11 items on a 5-point Likert scale Cooper et al. (2010, 2023), Gawronski et al. (2022) [30-32] 79% Overall performance (study-specific composite outcome) Composite score Weighted: 50% STAT, 25% CALM, 25% TEAM See above 77% Table 2: Composition of the main outcome score Three validated tools were used to assess medical and non-technical performance: the STAT, CALM, and TEAM tool. The overall quality of emergency medical care in our study was defined as a composite score of those three tools, weighted to reflect 50% medical skills (STAT) and 50% non-technical skills (CALM and TEAM). The estimated baseline performance for the composite score was derived from published reference values for the STAT, CALM, and TEAM tool according to their relative weight in the composite. The following secondary outcome parameters were assessed after each simulated scenario: the 2018 Lake Louise Score (LLS), a validated measure for the presence and severity of AMS [25] the Psychomotor Vigilance Task (PVT), a validated measure of reaction time [26] the Digit-Symbol Substitution Task (DSST), a validated measure of processing speed and working memory [26] the Balloon Analog Risk Test (BART), a validated measure of risk-taking behavior [26] a self-reported subjective performance on a 1–10 scale, where 5 reflected an average workday and 10 the best imaginable performance participants’ vital signs (blood pressure, heart rate, peripheral oxygen saturation (SpO 2 )) Adverse Events While at high altitude, participants were continually monitored for (serious) adverse events, defined as severe symptoms of AMS (Lake Louis Score 10-12), and signs of High Altitude Pulmonary or Cerebral Oedema. Analysis Descriptive summaries of participants’ characteristics, vital signs and performance metrics were presented with counts and frequencies (categorical variables) and with medians and interquartile ranges (numerical variables). The primary outcome was analysed by means of a generalized linear mixed model (GLMM) with the time points of the assessments (C1 to C4) as a fixed covariate and participant as a random intercept. The GLMM features a beta-distribution outcome to account for the restricted range of possible values (from 0 to 100%) of the primary outcome and accounts for the repeated measure design of the study. A likelihood ratio test was performed to assess whether the primary outcome differed across the four assessments. Secondary outcomes were assessed with a Friedman Rank Sum Test accounting for the repeated measure design and the possibility for skewed outcome distributions. The change of the secondary outcomes over time was assessed by means of the Kendall's W effect size. As exploratory analysis, the change of the primary outcome from baseline (C1) to acute high-altitude exposure (C2) was assessed with GLMM featuring a beta-distribution and the following covariates: performance at baseline, SpO 2 , LLS, age, and years of prehospital experience. The adjusted effect of each covariate on the performance during acute high-altitude exposure was presented graphically with estimated marginal means. The agreement between the three raters was examined with the Intraclass correlation coefficient (ICC) based on pooled scenarios for each outcome (i.e., STAT, CALM, TEAM). A sample size calculation performed before enrolment indicated that 18 participants would be required to detect a decrease in performance of 12.5% at 3,450 m compared with baseline (primary outcome) with 90.6% power at a significance level of α=0.05. This number was increased to 20 to account for potential dropouts. Due to health-related reasons unrelated to this study, three participants could not complete all four scenarios. Based on the study protocol, dropouts were not replaced. No imputation was performed for the missing outcomes and the final analysis was based on the n= 17 per-protocol participants. All computations were performed with R 4.0.2. Results Demographics Of the 17 participants that completed this study the median [IQR] age was 41 [34 to 48] years, and median [IQR] experience in prehospital emergency medicine was 8 [3 to 16] years. Eight were women (47%). Adverse Events No adverse events occurred in this study. Medical Performance During Acute High-Altitude Exposure Fig. 1 shows the median [IQR] composite medical performance across the four conditions, along with the median [IQR] scores of the three individual components comprising the composite score: the Simulation Team Assessment Tool (STAT)[27], the Concise Assessment of Leader Management (CALM)[28,29], and the Team Emergency Assessment Measure (TEAM).[30-32] All three score components follow the same pattern: from baseline (C1, 540 m), median scores were lower at 30 min at high altitude (C2, 3,450 m), and higher again in the supplemental oxygen (C3) and 20-hour (C4) conditions. In GLMM analysis, composite medical performance did not differ across the four conditions ( P= 0.082, Supplemental Digital Content 2). In particular, performance after 30 min at high altitude (C2) did not differ from baseline (C1) (-1% difference, 95%-CI: -5% to 3%, P= 0.53). Supplemental oxygen (C3) did not improve medical performance at high altitude compared with C2 (0% difference, 95%-CI: -4% to 4%, P= 0.94). 20 hours at high altitude (C4) improved performance compared with C2 (5% difference, 95%-CI: 1% to 9%, P= 0.03). Notably, this effect was not linked to improvements in AMS severity or SpO 2 (Fig. 2). Interrater Reliability The Intraclass Correlation Coefficient (ICC) of the three component scores comprising the composite performance were: 0.70 (95%-CI: 0.59 to 0.79) for STAT, 0.39 (95%-CI: 0.24 to 0.53) for CALM, and 0.50 (95%-CI: 0.36 to 0.63) for TEAM. SpO 2 and Acute Mountain Sickness The median [IQR] SpO 2 at baseline (C1) was 97% [96 to 98%]. As expected, median [IQR] SpO 2 dropped at C2 and C4 to 87% [86 to 88%] and 88% [55 to 91%], respectively. Supplemental oxygen (C3) restored median [IQR] SpO 2 to near-baseline levels (96% [94 to 98%]). AMS symptoms were consistently increased during all high-altitude scenarios (Fig. 2). Cognitive Performance Fig. 3 shows the results of the computer-based cognitive tests and the self-reported performance ratings. Reaction time (PVT), risk-taking behaviour (BART), and self-assessed cognitive performance remained stable under all conditions. In contrast, processing speed and working memory (DSST) declined after 30 min at high altitude (C2), with a substantial effect size ( Kendall’s W based on a Friedman Test= 0.35, P< 0.001). All cognitive outcome analyses were prespecified secondary analyses and should be interpreted as exploratory. Measurements were taken at all study conditions: baseline (C1, 540 m), acute high-altitude exposure (C2, 3,450 m), high altitude with 4 L/min supplemental oxygen (C3), and high altitude after 20 h of exposure (C4). Boxplots display the median and IQR; whiskers extend to the largest and smallest value within 1.5×IQR; values beyond are plotted individually. Effect of Sex on Medical Performance Sex had no effect on medical performance under any condition (overall 0% difference, 95%-CI: -8% to 7%, P= 0.92, Supplemental Digital Content 2). Effect of Experience on Medical Performance The best predictor for good performance after 30 min at high altitude (C2) was a good performance at baseline (C1). Performance at C1 and C2 correlated in a near-linear fashion; a 10% increase at baseline corresponded to a 10.6% increase at high altitude (95%-CI: 10.2 to 11.0%). Fig. 4 illustrates the effect of additional variables (age, experience, LLS, SpO₂) on performance after 30 min at high altitude (C2), adjusted for baseline performance. Prehospital experience was an independent predictor of performance during acute exposure to 3,450 m: after adjustment for baseline performance, an additional 10 years of experience was associated with better performance at C2 by 5.3% (95%-CI: 5.2 to 5.5%) in the exploratory adjusted model. Age, the severity of AMS symptoms (LLS), and SpO 2 values were not associated with medical performance. See Supplemental Digital Content 3 for full regression results. Discussion In this assessor-blinded randomized crossover simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in the composite quality score of simulated prehospital emergency care among non-acclimatized EMS physicians. Although median performance was numerically lower during acute altitude exposure than at baseline, the primary mixed-model analysis did not show a significant difference across study conditions. However, the confidence intervals indicate that small clinically relevant decrements cannot be excluded. These findings therefore suggest relative preservation of performance under the specific study conditions, rather than proving equivalence or non-inferiority of care at altitude. The quality of prehospital emergency medical care is challenging to measure. Previous high-altitude studies in emergency care have mainly examined isolated procedural or physically demanding tasks, particularly cardiopulmonary resuscitation, and generally found impaired compression quality or earlier fatigue at altitude.[6,15–19,33] Another procedure that has been studied at high altitude is the application of an orthopaedic external fixator to a plastic tibia. At 3,000 m, unacclimatized surgeons performed slightly worse, but still adequately according to the authors.[34] In contrast, our study focused on overall performance in complex, team-based emergency scenarios requiring diagnosis, prioritization, communication, and leadership. This broader approach better reflects real-life high-altitude EMS missions, where complex medical care is far more common than highly standardized procedures like CPR or isolated medical interventions.[35] Our findings suggest that under controlled simulation conditions, complex prehospital care by experienced physicians may be relatively resilient to acute exposure to 3,450 m. However, this should not be interpreted as evidence that all task domains are equally unaffected, particularly those involving sustained physical effort or fine motor skills. An important consideration is the use of a novel composite primary outcome combining medical and non-technical performance. Although all three component instruments (STAT, CALM, and TEAM) are externally validated[27–32], the weighting of these components within a single composite score was determined a priori by the investigators and remains partly subjective. This may limit interpretability of the absolute composite score and introduces uncertainty regarding the relative contribution of medical versus non-technical domains to the overall result. Reassuringly, all three components showed a similar directional pattern across conditions, but the composite should nevertheless be regarded as a pragmatic study-specific outcome rather than a universally established measure of care quality. Interrater reliability was moderate for the non-technical skill instruments and higher for the medical performance instrument. This may have reduced the sensitivity of the composite score to detect subtle altitude-related differences, especially in communication and leadership domains. Accordingly, a small true effect of altitude on overall performance cannot be ruled out. Supplemental oxygen improved oxygen saturation and appeared to attenuate the decline in processing speed (as measured by the DSST), but it was not associated with improved overall simulation performance. This may indicate that the degree of cognitive impairment induced by 3,450 m in this cohort was insufficient to translate into measurable reductions in global care quality, or that the study was underpowered to detect small performance effects. The findings therefore do not support a clear performance benefit of routine supplemental oxygen at this altitude under the present study conditions, but they do not exclude smaller benefits in other settings or at greater altitude. This is in line with the recent recommendations of the International Commission for Mountain Emergency Medicine and the International Society for Mountain Medicine advising the use of supplemental oxygen for all unacclimatized rescue personnel operating at above 3,500 m for longer than 30 min.[36] In this study, medical performance improved after 20 hours at 3,450 m. However, we consider acclimatization processes unlikely to explain this finding. Acclimatization is gradual, with SpO 2 typically increasing by about 1% per day at this altitude[37], and AMS symptoms peaking after the first night before subsiding.[8] This pattern aligns with our observations: neither SpO 2 nor AMS scores had markedly improved after 20 hours at 3,450 m. Thus, the observed improvement in performance after 20 hours at altitude compared with acute exposure may reflect a combination of other unmeasured factors—such as psychological or social adaptation—rather than physiological acclimatization alone. In our exploratory adjusted analyses, greater prehospital experience was associated with better performance during acute altitude exposure. This finding is clinically plausible, as experienced clinicians may rely more effectively on structured routines, pattern recognition, and team management strategies under physiologic stress.[38–41] Less experienced physicians may have perceived the simulated cases as more novel and complex, making their performance more vulnerable to altitude-related impairments. This observation is consistent with findings in aviation research.[42,43] However, given the small sample size and the exploratory nature of these models, this association should be interpreted cautiously and regarded as hypothesis-generating rather than confirmatory. Limitations This study has several limitations. First, despite efforts to maximize realism, simulation cannot fully reproduce the psychological stress, environmental complexity, and operational constraints of real high-altitude emergency missions. The scenarios were short, conducted indoors, and did not include major cold exposure, difficult terrain, or prolonged physical exertion. The observed results may therefore overestimate performance compared with real field conditions. Second, the final analysis included 17 participants, and the study was not designed as a non-inferiority trial. Consequently, the absence of a statistically significant difference between acute altitude exposure and baseline should not be interpreted as proof of equivalence. Small but clinically relevant decrements in performance remain possible within the reported confidence intervals. Third, the primary outcome was a study-specific composite score derived from validated component instruments[27–32], but the weighting of its components was investigator-defined and therefore partly subjective. In addition, interrater reliability was only moderate for two of the three component instruments, which may have reduced sensitivity for subtle between-condition differences. Fourth, the exploratory regression analyses should be interpreted with caution given the small sample size, the number of covariates considered, and the absence of adjustment for multiplicity. Finally, generalizability may be limited to relatively experienced physician-staffed EMS systems and to altitude exposure around 3,450 m. The findings may not generalize to less experienced providers, longer missions, harsher alpine environments, or substantially greater altitude. Conclusion In this assessor-blinded simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in overall simulated prehospital emergency care among non-acclimatized EMS physicians. However, because the study was not designed to test non-inferiority, small clinically relevant decrements cannot be excluded. Supplemental oxygen did not improve overall performance under the present study conditions. Abbreviations AMS : Acute mountain sickness BART : Balloon Analog Risk Test CALM : Concise Assessment of Leader Management CI : Confidence interval CPR : Cardiopulmonary resuscitation DSST : Digit-Symbol Substitution Task ECG : Electrocardiogram EMS : Emergency Medical Services GLMM : Generalized linear mixed model HEMS : Helicopter Emergency Medical Services HFSJG : High Altitude Research Stations Jungfraujoch and Gornergrat ICC : Intraclass correlation coefficient IQR : Interquartile range LLS : Lake Louise Score NACA : National Advisory Committee for Aeronautics PVT : Psychomotor Vigilance Task SpO 2 : Peripheral oxygen saturation STAT : Simulation Team Assessment Tool TEAM : Team Emergency Assessment Measure VAS : Visual analogue scale Declarations Ethics approval and consent to participate Ethical approval for this study was provided by the Cantonal Research Ethics Committee Bern, Switzerland (Chairperson Prof. Christian Seiler) on 8 July 2024 (ID: 2024-00237). Written informed consent was obtained from all participants. All study procedures were conducted in accordance with the Declaration of Helsinki. Consent for publication Not applicable. Availability of data and materials The deidentified datasets generated and/or analysed during the current study are not publicly available due to data protection considerations but are available from the corresponding author on reasonable request. Any custom-made code used in this study and the detailed trial protocol and statistical analysis plan are likewise available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding Sven Straumann was supported by a Young Investigator Grant from the Clinical Trial Unit, University Hospital Bern, awarded specifically for this study. Additional financial support was provided by the Department of Anaesthesiology and Pain Medicine, University Hospital Bern. Jürgen Knapp received ongoing protected research time funded by Swiss Air Rescue REGA, Zurich. The funding bodies had no role in the design of the study, collection, analysis, and interpretation of data, or in writing the manuscript. Authors’ contributions SS, JK, and MMB conceived the study, designed the trial, and obtained research funding. SS and JK obtained ethical approval. SS recruited participants. SS and JK supervised study conduct, data collection, data management, and quality control. SS, JK, ACZ, and LAW were directly involved in data collection. TH, FU, and FCF served as blinded outcome assessors. SS and MH provided statistical advice on study design and analysed the data. SS drafted the manuscript, and all authors contributed substantially to its revision. SS takes responsibility for the paper as a whole. All authors read and approved the final manuscript. 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Krage R, Zwaan L, Tjon Soei Len L, Kolenbrander MW, van Groeningen D, Loer SA, et al. Relationship between non-technical skills and technical performance during cardiopulmonary resuscitation: does stress have an influence? Emerg Med J 2017; 34 (11):728-733. Roach RC, Hackett PH, Oelz O, Bartsch P, Luks AM, MacInnis MJ, et al. The 2018 Lake Louise Acute Mountain Sickness Score. High Alt Med Biol 2018; 19 (1):4-6. Basner M, Hermosillo E, Nasrini J, Saxena S, Dinges DF, Moore TM, et al. Cognition test battery: Adjusting for practice and stimulus set effects for varying administration intervals in high performing individuals. J Clin Exp Neuropsychol 2020; 42 (5):516-529. Reid J, Stone K, Brown J, Caglar D, Kobayashi A, Lewis-Newby M, et al. The Simulation Team Assessment Tool (STAT): development, reliability and validation. Resuscitation 2012; 83 (7):879-886. Florez AR, Shepard LN, Frey ME, Justice LB, Constand SE, Gilbert GE, et al. The Concise Assessment of Leader Management Tool: Evaluation of Healthcare Provider Leadership During Real-Life Pediatric Emergencies. Simul Healthc 2023; 18 (1):24-31. Nadkarni LD, Roskind CG, Auerbach MA, Calhoun AW, Adler MD, Kessler DO. The Development and Validation of a Concise Instrument for Formative Assessment of Team Leader Performance During Simulated Pediatric Resuscitations. Simul Healthc 2018; 13 (2):77-82. Cooper S, Cant R, Porter J, Sellick K, Somers G, Kinsman L, et al. Rating medical emergency teamwork performance: development of the Team Emergency Assessment Measure (TEAM). Resuscitation 2010; 81 (4):446-452. Cooper S, Connell C, Cant R. Review article: Use of the Team Emergency Assessment Measure in the rating of emergency teams' non-technical skills: A mapping review. Emerg Med Australas 2023; 35 (3):375-383. Gawronski O, Thekkan KR, Genna C, Egman S, Sansone V, Erba I, et al. Instruments to evaluate non-technical skills during high fidelity simulation: A systematic review. Front Med (Lausanne) 2022; 9 :986296. Vogele A, van Veelen MJ, Dal Cappello T, Falla M, Nicoletto G, Dejaco A, et al. Effect of Acute Exposure to Altitude on the Quality of Chest Compression-Only Cardiopulmonary Resuscitation in Helicopter Emergency Medical Services Personnel: A Randomized, Controlled, Single-Blind Crossover Trial. J Am Heart Assoc 2021; 10 (23):e021090. Parker PJ, Manley AJ, Shand R, O'Hara JP, Mellor A. Working Memory Capacity and Surgical Performance While Exposed to Mild Hypoxic Hypoxemia. Aerosp Med Hum Perform 2017; 88 (10):918-923. Pietsch U, Knapp J, Mann M, Meuli L, Lischke V, Tissi M, et al. Incidence and challenges of helicopter emergency medical service (HEMS) rescue missions with helicopter hoist operations: analysis of 11,228 daytime and nighttime missions in Switzerland. Scand J Trauma Resusc Emerg Med 2021; 29 (1):92. McLaughlin K, Roy S, Falla M, Strapazzon G, Luks AM, Zafren K, et al. Pharmacological Prophylaxis and Supplemental Oxygen for Unacclimatized Rescuers at Very High Altitude: Scoping Review and 2025 Joint Recommendations of the International Commission for Mountain Emergency Medicine and the International Society for Mountain Medicine. High Alt Med Biol 2026; 27 (1):60-77. Dunnwald T, Kienast R, Niederseer D, Burtscher M. The Use of Pulse Oximetry in the Assessment of Acclimatization to High Altitude. Sensors (Basel) 2021; 21 (4). Buljac-Samardzic M, Dekker-van Doorn CM, Maynard MT. What Do We Really Know About Crew Resource Management in Healthcare?: An Umbrella Review on Crew Resource Management and Its Effectiveness. J Patient Saf 2021; 17 (8):e929-e958. Dijkstra FS, Renden PG, Meeter M, Schoonmade LJ, Krage R, van Schuppen H, et al. Learning about stress from building, drilling and flying: a scoping review on team performance and stress in non-medical fields. Scand J Trauma Resusc Emerg Med 2021; 29 (1):52. Muller MP, Hansel M, Fichtner A, Hardt F, Weber S, Kirschbaum C, et al. Excellence in performance and stress reduction during two different full scale simulator training courses: a pilot study. Resuscitation 2009; 80 (8):919-924. Thim T, Krarup NH, Grove EL, Rohde CV, Lofgren B. Initial assessment and treatment with the Airway, Breathing, Circulation, Disability, Exposure (ABCDE) approach. Int J Gen Med 2012; 5 :117-121. Bouak F, Vartanian O, Hofer K, Cheung B. Acute Mild Hypoxic Hypoxia Effects on Cognitive and Simulated Aircraft Pilot Performance. Aerosp Med Hum Perform 2018; 89 (6):526-535. Kryskow MA, Beidleman BA, Fulco CS, Muza SR. Performance during simple and complex military psychomotor tasks at various altitudes. Aviat Space Environ Med 2013; 84 (11):1147-1152. Additional Declarations No competing interests reported. Supplementary Files SupplementaryDigitalContent1.docx SupplementaryDigitalContent2.docx SupplementaryDigitalContent3neu.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 13 May, 2026 Reviewers agreed at journal 28 Apr, 2026 Reviews received at journal 20 Apr, 2026 Reviewers agreed at journal 10 Apr, 2026 Reviewers invited by journal 08 Apr, 2026 Editor assigned by journal 31 Mar, 2026 Submission checks completed at journal 31 Mar, 2026 First submitted to journal 30 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-9268709\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":621099154,\"identity\":\"d9e6e89e-a36f-4794-a08d-bcf771722225\",\"order_by\":0,\"name\":\"Sven Straumann\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Sven\",\"middleName\":\"\",\"lastName\":\"Straumann\",\"suffix\":\"\"},{\"id\":621099158,\"identity\":\"5cf88971-3d53-4bdb-8500-b05055f36be2\",\"order_by\":1,\"name\":\"Thomas Heidt\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Thomas\",\"middleName\":\"\",\"lastName\":\"Heidt\",\"suffix\":\"\"},{\"id\":621099159,\"identity\":\"22e4449b-d34e-4c1d-b59a-89ad07b23280\",\"order_by\":2,\"name\":\"Fiona Uhor\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Fiona\",\"middleName\":\"\",\"lastName\":\"Uhor\",\"suffix\":\"\"},{\"id\":621099160,\"identity\":\"f826d418-ab87-43de-89e8-34ee0121a669\",\"order_by\":3,\"name\":\"Fabienne Frickmann\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Fabienne\",\"middleName\":\"\",\"lastName\":\"Frickmann\",\"suffix\":\"\"},{\"id\":621099162,\"identity\":\"2080ec6d-780d-4cc9-b28a-70c5b7561cd3\",\"order_by\":4,\"name\":\"Anna Zimmermann\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Anna\",\"middleName\":\"\",\"lastName\":\"Zimmermann\",\"suffix\":\"\"},{\"id\":621099163,\"identity\":\"1bea6a33-7e43-4bb8-90e1-6eb5b31fb966\",\"order_by\":5,\"name\":\"Lea Wahl\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Lea\",\"middleName\":\"\",\"lastName\":\"Wahl\",\"suffix\":\"\"},{\"id\":621099167,\"identity\":\"4998aad8-a40f-41ff-be4b-66aa23408aef\",\"order_by\":6,\"name\":\"Markus Huber\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Markus\",\"middleName\":\"\",\"lastName\":\"Huber\",\"suffix\":\"\"},{\"id\":621099168,\"identity\":\"513ae579-d86d-43d6-ac47-49a0f10734d4\",\"order_by\":7,\"name\":\"Marc Berger\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Klinikum Ludwigsburg\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Marc\",\"middleName\":\"\",\"lastName\":\"Berger\",\"suffix\":\"\"},{\"id\":621099170,\"identity\":\"cb4e232a-7f62-4e90-bca0-0c30adb9ec80\",\"order_by\":8,\"name\":\"Jürgen Knapp\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIiWNgGAWjYBACxgYoQwJMVoAo5gaEMGEtZyQgYvi0wAFYC2MbA2EtzDOSj338UnGHQXJ287PHhfMs8uTbGxsYfu7A47AZacmzZc48Y5CWOWZuPHObRLHBmYMNjL1n8GnJMWaWbDvMICeRYCbNu00icYNEYgMzxIW4tOR/Zpb8B9KS/k2ad45E4vz5DwlpyWFm/NhwmEFaIgdoSwPQihuMBLT0PDNmZjh2mEdyRk658YxjQIedSWw42ItHi2F78mPGHzWH5SRupG97XFBTlzi//fDBBz/xaWkABjQPAwMQMbAxw0QP4NbAwCAPctwPCBuhZRSMglEwCkYBMgAAEO9SMAptu3oAAAAASUVORK5CYII=\",\"orcid\":\"\",\"institution\":\"University Hospital of Bern\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Jürgen\",\"middleName\":\"\",\"lastName\":\"Knapp\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2026-03-30 14:54:48\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-9268709/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-9268709/v1\",\"draftVersion\":[],\"editorialEvents\":[],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":108005899,\"identity\":\"8495e1a7-fc89-4b92-9117-1057c4e1d6b6\",\"added_by\":\"auto\",\"created_at\":\"2026-04-28 12:50:27\",\"extension\":\"png\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":115265,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eMain outcome: composite performance score\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e(\\u003cstrong\\u003eA\\u003c/strong\\u003e) Participants’ performance at baseline (C1, 540 m), during acute high-altitude exposure (C2, 3450 m), at high altitude with 4 L/min supplemental oxygen (C3), and at high altitude after 20 hours of exposure (C4). The primary outcome shown in (A) is the percentage they achieved in a weighted composite scoring tool evaluating medical skills (STAT score, weighted at 50%) and non-technical skills (CALM and TEAM scores, each weighted at 25%). Boxplots display the median and IQR; whiskers extend to the largest and smallest value within 1.5×IQR; values beyond are plotted individually. Grey lines represent results from individual participants.\\u003cstrong\\u003e (B)\\u003c/strong\\u003e Median and IQR of the individual scores comprising the composite score (STAT, CALM, and TEAM) across all conditions are shown. Percentages represent the proportion of the maximum possible score achieved.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/c41d7affd41f4da64b141ca4.png\"},{\"id\":107245067,\"identity\":\"9301c0da-f1c7-4ff3-8bdb-ac76733e1471\",\"added_by\":\"auto\",\"created_at\":\"2026-04-19 07:57:10\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":159767,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003ePeripheral oxygen saturation and acute mountain sickness score\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e(\\u003cstrong\\u003eA\\u003c/strong\\u003e) Peripheral oxygen saturation (SpO\\u003csub\\u003e2\\u003c/sub\\u003e) and (\\u003cstrong\\u003eB\\u003c/strong\\u003e) severity of acute mountain sickness (AMS, based on the Lake Louise Score) were measured directly after completion of the simulated medical scenarios under all conditions: baseline (C1, 540 m), acute high-altitude exposure (C2, 3,450 m), high altitude with 4 L/min supplemental oxygen (C3), and high altitude after 20 h of exposure (C4). The presence of AMS is defined as a Lake Louise Score of ≥3 points in the presence of headache. Boxplots display the median and IQR; whiskers extend to the largest and smallest value within 1.5×IQR; values beyond are plotted individually.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/ea94320220a47cdfa9289d3d.png\"},{\"id\":107484438,\"identity\":\"aebb8841-2dea-4960-8582-81496aedbadb\",\"added_by\":\"auto\",\"created_at\":\"2026-04-22 02:32:01\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":232040,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eCognitive performance\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eResults of the computer-based tests of cognitive performance. (\\u003cstrong\\u003eA\\u003c/strong\\u003e) reaction time in seconds, according to the Psychomotor Vigilance Test (PVT). (\\u003cstrong\\u003eB\\u003c/strong\\u003e) Processing speed and working memory, according to the Digit-Symbol Substitution Task (DSST); higher scores correspond to a better performance. (\\u003cstrong\\u003eC\\u003c/strong\\u003e) Risk-taking behavior, according to the Balloon Analog Risk Test (BART); higher scores correspond to higher risk-taking behavior. (\\u003cstrong\\u003eD\\u003c/strong\\u003e) Own assessment of current cognitive performance on a visual-analog scale (VAS 1-10; 5=average, higher=better, lower=worse).\\u003c/p\\u003e\\n\\u003cp\\u003eMeasurements were taken at all study conditions: baseline (C1, 540 m), acute high-altitude exposure (C2, 3,450 m), high altitude with 4 L/min supplemental oxygen (C3), and high altitude after 20 h of exposure (C4). Boxplots display the median and IQR; whiskers extend to the largest and smallest value within 1.5×IQR; values beyond are plotted individually.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/7b9f40ee873f18258685a0f0.png\"},{\"id\":107245071,\"identity\":\"2e716b17-5d1f-4529-bc1e-a75014af422d\",\"added_by\":\"auto\",\"created_at\":\"2026-04-19 07:57:10\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":66188,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003ePredictors of medical performance under acute exposure to 3,450\\u0026nbsp;m\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe effect of (A) age, (B) experience as a pre-hospital physician in years, (C) AMS as measured by the Lake Louise Score, and (D) SpO\\u003csub\\u003e2\\u003c/sub\\u003e on medical performance after 30 min at 3,450 m. Parameters are adjusted for baseline performance. The grey overlay represents estimated marginal means. Experience as a pre-hospital physician was associated with better performance: an additional 10 years of experience improved performance at high altitude by 5.3% (95%-CI: 5.2–5.5%).\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/c089cb0baf491c92bef9186f.png\"},{\"id\":108008328,\"identity\":\"2ec0dba3-3729-4a12-b11d-1838e3c28cf1\",\"added_by\":\"auto\",\"created_at\":\"2026-04-28 13:06:18\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":805044,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/cfcaa785-d354-40c1-b05f-3ebc372552a1.pdf\"},{\"id\":107245064,\"identity\":\"4c3a5524-1d64-47cb-96b4-5e664ae5be5b\",\"added_by\":\"auto\",\"created_at\":\"2026-04-19 07:57:10\",\"extension\":\"docx\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":53622,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"SupplementaryDigitalContent1.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/102f2e31e19d0693cd2cdcc3.docx\"},{\"id\":107482627,\"identity\":\"c3628601-58c1-45f7-a22b-80c8e9892947\",\"added_by\":\"auto\",\"created_at\":\"2026-04-22 02:24:14\",\"extension\":\"docx\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":22843,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"SupplementaryDigitalContent2.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/1451ba4aef5c1c4880507d2e.docx\"},{\"id\":107245069,\"identity\":\"ac57f069-28f5-421e-9fad-ae81169c3f09\",\"added_by\":\"auto\",\"created_at\":\"2026-04-19 07:57:10\",\"extension\":\"docx\",\"order_by\":2,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":17615,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"SupplementaryDigitalContent3neu.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-9268709/v1/5ab14466881e01d0a624cbf6.docx\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Quality of prehospital emergency care at high altitude: a randomized assessor-blinded simulation crossover study\",\"fulltext\":[{\"header\":\"Introduction\",\"content\":\"\\u003ch2\\u003e\\u003cstrong\\u003eBackground\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eHigh-quality prehospital emergency medical care by expert teams improves patient survival and outcomes at hospital discharge.[1-4] Maintaining a high standard of prehospital care is therefore essential even under the demanding conditions of high-altitude rescue. However, high-altitude environments pose unique challenges that may limit the quality of medical care.[5-7]\\u003c/p\\u003e\\n\\u003cp\\u003eThe defining feature of the environment at high altitude is the nonlinear decrease in barometric pressure, which leads to a reduction in the partial pressure of oxygen (pO\\u003csub\\u003e2\\u003c/sub\\u003e) at every point along the oxygen transport chain, i.e. from the lungs to the mitochondria. If the body\\u0026rsquo;s adaptive mechanisms fail to compensate for the lack of oxygen, symptoms of acute mountain sickness (AMS) may follow: headache, nausea, vomiting, fatigue, weakness, and dizziness/light-headedness.[8] In addition, hypobaric hypoxia can also impair higher cognitive functions, though the lowest altitude at which this becomes evident is subject to a considerable interindividual and activity-related variability.[9,10] If impairments arise, serious and even fatal errors may follow.[11]\\u003c/p\\u003e\\n\\u003cp\\u003eTo date, research on the effects of acute high-altitude exposure on the quality of prehospital emergency medical care has focused primarily on the quality of cardiopulmonary resuscitation (CPR). Findings suggest that the quality of chest compressions declines[12-14], and rescuer fatigue occurs faster.[15-19] However, high-quality mountain rescue requires far more than adequate CPR; it demands complex medical, technical, and cognitive skills\\u0026mdash;all of which may be impaired at high altitude, potentially compromising treatment quality.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eObjectives\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe primary objective of this study was to assess whether acute high-altitude exposure (3,450 m) is associated with reduced quality of prehospital emergency medical care provided by non-acclimatized Emergency Medical Services (EMS) physicians during short, controlled, high-fidelity simulated emergency scenarios, compared with low altitude (540 m).\\u003c/p\\u003e\\n\\u003cp\\u003eSecondary analyses explored whether medical performance at high altitude was influenced by supplemental oxygen or a one-night stay at this altitude, and whether it was associated with years of prehospital experience, AMS severity, sex, or cognitive function.\\u003c/p\\u003e\"},{\"header\":\"Methods\",\"content\":\"\\u003ch2\\u003e\\u003cstrong\\u003eEthics approval\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eEthical approval for this study was provided by the \\u003cem\\u003eCantonal Research Ethics Committee\\u003c/em\\u003e\\u003cem\\u003e\\u0026nbsp;Bern\\u003c/em\\u003e, Switzerland (Chairperson Prof. Christian Seiler) on 8 July 2024 (ID: 2024-00237). Written informed consent was obtained from all participants, and all study procedures were in accordance with the Declaration of Helsinki.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eTrial registration\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe trial was registered prior to the start of enrolment at ClinicalTrials.gov (NCT06446427, registration date: 6 June 2024)\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eStudy design\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe study followed a randomized crossover design.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eParticipants\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eWe enrolled 20 EMS physicians (10 female). Inclusion criteria were:\\u003c/p\\u003e\\n\\u003cul\\u003e\\n \\u003cli\\u003e\\u0026ge;2 years of training in anaesthesiology\\u003c/li\\u003e\\n \\u003cli\\u003eCertified prehospital Emergency Medical Services (EMS) physician\\u003c/li\\u003e\\n \\u003cli\\u003e\\u0026ge;3 months of full-time prehospital work\\u003c/li\\u003e\\n \\u003cli\\u003eMedical team leader in \\u0026ge;50 life-threatening prehospital cases (National Advisory Committee for Aeronautics (NACA) score\\u0026ge;4)\\u003c/li\\u003e\\n\\u003c/ul\\u003e\\n\\u003cp\\u003eExclusion criteria were:\\u003c/p\\u003e\\n\\u003cul\\u003e\\n \\u003cli\\u003eAny medical condition known to place the participant at higher risk for hypoxia-induced adverse events (cardiovascular, pulmonary, neurological, otherwise)\\u003c/li\\u003e\\n \\u003cli\\u003eTravel to \\u0026ge;2500 m within 4 weeks before the study (pre-acclimatization)\\u003c/li\\u003e\\n\\u003c/ul\\u003e\\n\\u003cp\\u003eParticipants were recruited by announcements in online and print media (between 8 July 2024 and 14 August 2024). EMS physicians were chosen because they form the clinical core of physician-staffed medical emergency teams across Europe and are routinely responsible for advanced medical decision-making in high-altitude rescue.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eSetting\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe study was conducted between September 2024 and January 2025. The participants completed four simulated medical scenarios: one at the University Hospital Bern, Switzerland (540 m) and three at the High-altitude\\u0026nbsp;Research Station Jungfraujoch, Switzerland\\u0026nbsp;(3,450 m). The ascent to the research station was a standardized passive transport by train and gondola over 45 minutes, starting at 937 m. Participants were not allowed to use medication known to ameliorate AMS symptoms, such as acetazolamide or ibuprofen.[20,21] Participants were allowed to use the time between scenarios at leisure, but were not allowed any physically strenuous activities or the consumption of alcohol.\\u003c/p\\u003e\\n\\u003cp\\u003eThe specific conditions (C1-C4) under which the participants completed the simulated scenarios are outlined in Table 1. The order of the scenarios was randomized from a balanced subset of 20 of all possible 24 permutations, such that each scenario occurred equally often under each condition across participants. This was done to eliminate order effects in case any scenarios were felt to be more difficult than others.\\u003c/p\\u003e\\n\\u003ctable border=\\\"1\\\" cellspacing=\\\"0\\\" cellpadding=\\\"0\\\"\\u003e\\n \\u003ctbody\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 104px;\\\"\\u003e\\n \\u003cp\\u003eCondition\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 65px;\\\"\\u003e\\n \\u003cp\\u003eCondition code\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 60px;\\\"\\u003e\\n \\u003cp\\u003eAltitude above sea level\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 111px;\\\"\\u003e\\n \\u003cp\\u003eLocation\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 92px;\\\"\\u003e\\n \\u003cp\\u003eTime at high-altitude before scenario\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 108px;\\\"\\u003e\\n \\u003cp\\u003eGas administered via nasal cannula\\u0026nbsp;\\u003cbr\\u003e\\u0026nbsp;(4 L/min)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 104px;\\\"\\u003e\\n \\u003cp\\u003eBaseline\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 65px;\\\"\\u003e\\n \\u003cp\\u003eC1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 60px;\\\"\\u003e\\n \\u003cp\\u003e540 m\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 111px;\\\"\\u003e\\n \\u003cp\\u003eBern, Switzerland\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 92px;\\\"\\u003e\\n \\u003cp\\u003eNot applicable\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 108px;\\\"\\u003e\\n \\u003cp\\u003ePlacebo (pressurized air)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 104px;\\\"\\u003e\\n \\u003cp\\u003eAcute high-altitude exposure\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 65px;\\\"\\u003e\\n \\u003cp\\u003eC2\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 60px;\\\"\\u003e\\n \\u003cp\\u003e3,450 m\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 111px;\\\"\\u003e\\n \\u003cp\\u003eJungfraujoch Research Station\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 92px;\\\"\\u003e\\n \\u003cp\\u003e0.5 h\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 108px;\\\"\\u003e\\n \\u003cp\\u003ePlacebo (pressurized air)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 104px;\\\"\\u003e\\n \\u003cp\\u003eSupplemental oxygen\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 65px;\\\"\\u003e\\n \\u003cp\\u003eC3\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 60px;\\\"\\u003e\\n \\u003cp\\u003e3,450 m\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 111px;\\\"\\u003e\\n \\u003cp\\u003eJungfraujoch Research Station\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 92px;\\\"\\u003e\\n \\u003cp\\u003e4 h\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 108px;\\\"\\u003e\\n \\u003cp\\u003e100% Oxygen\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 104px;\\\"\\u003e\\n \\u003cp\\u003eAfter 20 h at high altitude\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 65px;\\\"\\u003e\\n \\u003cp\\u003eC4\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 60px;\\\"\\u003e\\n \\u003cp\\u003e3,450 m\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 111px;\\\"\\u003e\\n \\u003cp\\u003eJungfraujoch Research Station\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 92px;\\\"\\u003e\\n \\u003cp\\u003e20 h\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd valign=\\\"top\\\" style=\\\"width: 108px;\\\"\\u003e\\n \\u003cp\\u003ePlacebo (pressurized air)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003c/tbody\\u003e\\n\\u003c/table\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eTable 1: Study conditions\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eConditions (C1 to C4) under which the simulated emergency scenarios were performed.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eIntervention\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe following four high-fidelity emergency medical scenarios were designed:\\u003c/p\\u003e\\n\\u003col\\u003e\\n \\u003cli\\u003ePolytrauma with tension pneumothorax and open ankle fracture\\u003c/li\\u003e\\n \\u003cli\\u003eMyocardial infarction in an elderly patient, presenting with atypical symptoms (abdominal discomfort) and progressing to cardiac arrest\\u003c/li\\u003e\\n \\u003cli\\u003eRecurrent epileptic seizures and respiratory failure in a five-month-old baby with meningitis and pulmonary aspiration, mother present on scene\\u003c/li\\u003e\\n \\u003cli\\u003eSevere accidental hypothermia with unstable bradyarrhythmia, progressing to ventricular fibrillation due to rescue collapse\\u003c/li\\u003e\\n\\u003c/ol\\u003e\\n\\u003cp\\u003ePatients were played by two medical students, procedures (such as CPR, tracheal intubation, or chest tubes) were performed on mannequins, and clinical findings were shown via audio, video, or images (e.g., injuries, ECGs, breathing sounds). Participants had a full set of real equipment at their disposal and could delegate tasks to an assisting paramedic in each case. The role of the paramedic was filled by an experienced EMS physician. Participants were allowed to use supporting aids (e.g., paediatric dose sheets or calculators) consistent with real-life clinical practice.\\u003c/p\\u003e\\n\\u003cp\\u003eParticipants had no prior knowledge about the nature of the scenarios and were not allowed to share information with other participants.\\u003c/p\\u003e\\n\\u003cp\\u003eEach simulated scenario lasted about 20 min, took place in a controlled indoor environment, and was video recorded for later analyses. Participants wore nasal cannulas in all conditions, but supplemental oxygen (4 L/min) was delivered only in C3. In the other three conditions (C1, C2, C4), identical flow rates of pressurized air (21% O\\u003csub\\u003e2\\u003c/sub\\u003e) were used as placebo.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eMeasurements\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eVideo recordings of all simulated scenarios were rated independently by three blinded outcome assessors (board-certified anaesthesiologists, experienced in both prehospital emergency medicine and simulation training). This video-based rating allowed for repeated, independent assessments and blinding, as widely recommended in recent literature.[22,23] To ensure assessor blinding to scenario location (low vs. high altitude), an identical setup and backdrop were used for all video recordings. Using validated scoring tools (Table 2), the assessors evaluated medical, communication, and leadership skills. Their independent ratings were averaged for analysis. The primary outcome was the overall performance, defined as a weighted composite score consisting of 50% medical skills and 50% non-technical skills (communication and leadership). Equal weighting was chosen a priori to reflect the established importance of non-technical skills, such as leadership and communication, for safe and effective prehospital emergency care, particularly in complex team-based scenarios.[24] See Supplemental Digital Content 1\\u003cstrong\\u003e\\u0026nbsp;\\u003c/strong\\u003efor the detailed scoring matrix used to evaluate each scenario.\\u003c/p\\u003e\\n\\u003ctable border=\\\"0\\\" cellspacing=\\\"0\\\" cellpadding=\\\"0\\\" width=\\\"601\\\"\\u003e\\n \\u003ctbody\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 132px;\\\"\\u003e\\n \\u003cp\\u003e\\u003cstrong\\u003eType of assessment\\u003c/strong\\u003e\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003e\\u003cstrong\\u003eTool\\u003c/strong\\u003e\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 142px;\\\"\\u003e\\n \\u003cp\\u003e\\u003cstrong\\u003eScore description\\u003c/strong\\u003e\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003e\\u003cstrong\\u003eReferences / Validation\\u003c/strong\\u003e\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp\\u003e\\u003cstrong\\u003eApproximate baseline performance reported in the literature\\u003c/strong\\u003e\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 132px;\\\"\\u003e\\n \\u003cp\\u003eMedical skills\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eModified Simulation Team Assessment Tool (STAT)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 142px;\\\"\\u003e\\n \\u003cp\\u003eAssesses scenario-specific medical actions required for adequate patient care using a 3-point Likert scale\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eReid et al. (2012)\\u0026nbsp;[27]\\u0026nbsp;\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp\\u003e84%\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 132px;\\\"\\u003e\\n \\u003cp\\u003eNon-technical skills\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eConcise Assessment of Leader Management (CALM)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 142px;\\\"\\u003e\\n \\u003cp\\u003eAssesses leadership, communication, and crisis resource management using 15 items on a 4-point Likert scale\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eNadkarni et al. (2018), Florez et al. (2023)\\u0026nbsp;[28,29]\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp\\u003e60%\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 132px;\\\"\\u003e\\n \\u003cp\\u003eNon-technical skills\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eTeam Emergency Assessment Measure (TEAM)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 142px;\\\"\\u003e\\n \\u003cp\\u003eAssesses teamwork, task management, and crisis resource management using 11 items on a 5-point Likert scale\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eCooper et al. (2010, 2023), Gawronski et al.\\u0026nbsp;(2022) [30-32]\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp\\u003e79%\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 132px;\\\"\\u003e\\n \\u003cp\\u003eOverall performance (study-specific composite outcome)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eComposite score\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 142px;\\\"\\u003e\\n \\u003cp\\u003eWeighted: 50% STAT, 25% CALM, 25% TEAM\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 113px;\\\"\\u003e\\n \\u003cp\\u003eSee above\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp\\u003e77%\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003c/tbody\\u003e\\n\\u003c/table\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eTable 2: Composition of the main outcome score\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThree validated tools were used to assess medical and non-technical performance: the STAT, CALM, and TEAM tool. The overall quality of emergency medical care in our study was defined as a composite score of those three tools, weighted to reflect 50% medical skills (STAT) and 50% non-technical skills (CALM and TEAM). The estimated baseline performance for the composite score was derived from published reference values for the STAT, CALM, and TEAM tool according to their relative weight in the composite.\\u003c/p\\u003e\\n\\u003cp\\u003eThe following secondary outcome parameters were assessed after each simulated scenario:\\u003c/p\\u003e\\n\\u003cul\\u003e\\n \\u003cli\\u003ethe 2018 Lake Louise Score (LLS), a validated measure for the presence and severity of AMS [25]\\u003c/li\\u003e\\n \\u003cli\\u003ethe Psychomotor Vigilance Task (PVT), a validated measure of reaction time [26]\\u003c/li\\u003e\\n \\u003cli\\u003ethe Digit-Symbol Substitution Task (DSST), a validated measure of processing speed and working memory [26]\\u003c/li\\u003e\\n \\u003cli\\u003ethe Balloon Analog Risk Test (BART), a validated measure of risk-taking behavior [26]\\u003c/li\\u003e\\n \\u003cli\\u003ea self-reported subjective performance on a 1\\u0026ndash;10 scale, where 5 reflected an average workday and 10 the best imaginable performance\\u003c/li\\u003e\\n \\u003cli\\u003eparticipants\\u0026rsquo; vital signs (blood pressure, heart rate, peripheral oxygen saturation (SpO\\u003csub\\u003e2\\u003c/sub\\u003e))\\u003c/li\\u003e\\n\\u003c/ul\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAdverse Events\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eWhile at high altitude, participants were continually monitored for (serious) adverse events, defined as severe symptoms of AMS (Lake Louis Score 10-12), and signs of High Altitude Pulmonary or Cerebral Oedema.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eAnalysis\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eDescriptive summaries of participants\\u0026rsquo; characteristics, vital signs and performance metrics were presented with counts and frequencies (categorical variables) and with medians and interquartile ranges (numerical variables).\\u003c/p\\u003e\\n\\u003cp\\u003eThe primary outcome was analysed by means of a generalized linear mixed model (GLMM) with the time points of the assessments (C1 to C4) as a fixed covariate and participant as a random intercept. The GLMM features a beta-distribution outcome to account for the restricted range of possible values (from 0 to 100%) of the primary outcome and accounts for the repeated measure design of the study. A likelihood ratio test was performed to assess whether the primary outcome differed across the four assessments. Secondary outcomes were assessed with a Friedman Rank Sum Test accounting for the repeated measure design and the possibility for skewed outcome distributions. The change of the secondary outcomes over time was assessed by means of the Kendall\\u0026apos;s W effect size.\\u003c/p\\u003e\\n\\u003cp\\u003eAs exploratory analysis, the change of the primary outcome from baseline (C1) to acute high-altitude exposure (C2) was assessed with GLMM featuring a beta-distribution and the following covariates: performance at baseline, SpO\\u003csub\\u003e2\\u003c/sub\\u003e, LLS, age, and years of prehospital experience. The adjusted effect of each covariate on the performance during acute high-altitude exposure was presented graphically with estimated marginal means. The agreement between the three raters was examined with the Intraclass correlation coefficient (ICC) based on pooled scenarios for each outcome (i.e., STAT, CALM, TEAM).\\u003c/p\\u003e\\n\\u003cp\\u003eA sample size calculation performed before enrolment indicated that 18 participants would be required to detect a decrease in performance of 12.5% at 3,450 m compared with baseline (primary outcome) with 90.6% power at a significance level of \\u0026alpha;=0.05. This number was increased to 20 to account for potential dropouts. Due to health-related reasons unrelated to this study, three participants could not complete all four scenarios. Based on the study protocol, dropouts were not replaced. No imputation was performed for the missing outcomes and the final analysis was based on the \\u003cem\\u003en=\\u003c/em\\u003e17 per-protocol participants. All computations were performed with R 4.0.2.\\u0026nbsp;\\u003c/p\\u003e\"},{\"header\":\"Results\",\"content\":\"\\u003ch2\\u003e\\u003cstrong\\u003eDemographics\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eOf the 17 participants that completed this study the median [IQR] age was 41 [34 to 48] years, and median [IQR] experience in prehospital emergency medicine was 8 [3 to 16] years. Eight were women (47%).\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eAdverse Events\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eNo adverse events occurred in this study.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eMedical Performance During Acute High-Altitude Exposure\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFig. 1\\u003c/strong\\u003e shows the median [IQR] composite medical performance across the four conditions, along with the median [IQR] scores of the three individual components comprising the composite score: the Simulation Team Assessment Tool (STAT)[27], the Concise Assessment of Leader Management (CALM)[28,29], and the Team Emergency Assessment Measure (TEAM).[30-32] All three score components follow the same pattern: from baseline (C1, 540 m), median scores were lower at 30 min at high altitude (C2, 3,450 m), and higher again in the supplemental oxygen (C3) and 20-hour (C4) conditions.\\u003c/p\\u003e\\n\\u003cp\\u003eIn GLMM analysis, composite medical performance did not differ across the four conditions (\\u003cem\\u003eP=\\u003c/em\\u003e0.082, Supplemental Digital Content 2). In particular, performance after 30 min at high altitude (C2) did not differ from baseline (C1) (-1% difference, 95%-CI: -5% to 3%, \\u003cem\\u003eP=\\u003c/em\\u003e0.53). Supplemental oxygen (C3) did not improve medical performance at high altitude compared with C2 (0% difference, 95%-CI: -4% to 4%, \\u003cem\\u003eP=\\u003c/em\\u003e0.94). 20 hours at high altitude (C4) improved performance compared with C2 (5% difference, 95%-CI: 1% to 9%, \\u003cem\\u003eP=\\u003c/em\\u003e0.03). Notably, this effect was not linked to improvements in AMS severity or SpO\\u003csub\\u003e2\\u003c/sub\\u003e (Fig. 2).\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eInterrater Reliability\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe Intraclass Correlation Coefficient (ICC) of the three component scores comprising the composite performance were: \\u003cem\\u003e0.70 (95%-CI: 0.59 to 0.79)\\u003c/em\\u003e for STAT, 0.39 (95%-CI: 0.24 to 0.53) for CALM, and 0.50 (95%-CI: 0.36 to 0.63) for TEAM.\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eSpO\\u003csub\\u003e2\\u003c/sub\\u003e and Acute Mountain Sickness\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe median [IQR] SpO\\u003csub\\u003e2\\u003c/sub\\u003e at baseline (C1) was 97% [96 to 98%]. As expected, median [IQR] SpO\\u003csub\\u003e2\\u003c/sub\\u003e dropped at C2 and C4 to 87% [86 to 88%] and 88% [55 to 91%], respectively. Supplemental oxygen (C3) restored median [IQR] SpO\\u003csub\\u003e2\\u003c/sub\\u003e to near-baseline levels (96% [94 to 98%]). AMS symptoms were consistently increased during all high-altitude scenarios (Fig. 2).\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eCognitive Performance\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eFig. 3 shows the results of the computer-based cognitive tests and the self-reported performance ratings. Reaction time (PVT), risk-taking behaviour (BART), and self-assessed cognitive performance remained stable under all conditions. In contrast, processing speed and working memory (DSST) declined after 30 min at high altitude (C2), with a substantial effect size (\\u003cem\\u003eKendall\\u0026rsquo;s W based on a Friedman Test=\\u003c/em\\u003e0.35, \\u003cem\\u003eP\\u0026lt;\\u003c/em\\u003e0.001). All cognitive outcome analyses were prespecified secondary analyses and should be interpreted as exploratory.\\u003c/p\\u003e\\n\\u003cp\\u003eMeasurements were taken at all study conditions: baseline (C1, 540 m), acute high-altitude exposure (C2, 3,450 m), high altitude with 4 L/min supplemental oxygen (C3), and high altitude after 20 h of exposure (C4). Boxplots display the median and IQR; whiskers extend to the largest and smallest value within 1.5\\u0026times;IQR; values beyond are plotted individually.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eEffect of Sex on Medical Performance\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eSex had no effect on medical performance under any condition (overall 0% difference, 95%-CI: -8% to 7%, \\u003cem\\u003eP=\\u003c/em\\u003e0.92, Supplemental Digital Content 2).\\u003c/p\\u003e\\n\\u003ch2\\u003e\\u003cstrong\\u003eEffect of Experience on Medical Performance\\u003c/strong\\u003e\\u003c/h2\\u003e\\n\\u003cp\\u003eThe best predictor for good performance after 30 min at high altitude (C2) was a good performance at baseline (C1). Performance at C1 and C2 correlated in a near-linear fashion; a 10% increase at baseline corresponded to a 10.6% increase at high altitude (95%-CI: 10.2 to 11.0%).\\u003c/p\\u003e\\n\\u003cp\\u003eFig. 4 illustrates the effect of additional variables (age, experience, LLS, SpO₂) on performance after 30 min at high altitude (C2), adjusted for baseline performance. Prehospital experience was an independent predictor of performance during acute exposure to 3,450 m: after adjustment for baseline performance, an additional 10 years of experience was associated with better performance at C2 by 5.3% (95%-CI: 5.2 to 5.5%) in the exploratory adjusted model. Age, the severity of AMS symptoms (LLS), and SpO\\u003csub\\u003e2\\u003c/sub\\u003e values were not associated with medical performance. See Supplemental Digital Content 3 for full regression results.\\u003c/p\\u003e\"},{\"header\":\"Discussion\",\"content\":\"\\u003cp\\u003eIn this assessor-blinded randomized crossover simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in the composite quality score of simulated prehospital emergency care among non-acclimatized EMS physicians. Although median performance was numerically lower during acute altitude exposure than at baseline, the primary mixed-model analysis did not show a significant difference across study conditions. However, the confidence intervals indicate that small clinically relevant decrements cannot be excluded. These findings therefore suggest relative preservation of performance under the specific study conditions, rather than proving equivalence or non-inferiority of care at altitude.\\u003c/p\\u003e \\u003cp\\u003eThe quality of prehospital emergency medical care is challenging to measure. Previous high-altitude studies in emergency care have mainly examined isolated procedural or physically demanding tasks, particularly cardiopulmonary resuscitation, and generally found impaired compression quality or earlier fatigue at altitude.[6,15\\u0026ndash;19,33] Another procedure that has been studied at high altitude is the application of an orthopaedic external fixator to a plastic tibia. At 3,000 m, unacclimatized surgeons performed slightly worse, but still adequately according to the authors.[34] In contrast, our study focused on overall performance in complex, team-based emergency scenarios requiring diagnosis, prioritization, communication, and leadership. This broader approach better reflects real-life high-altitude EMS missions, where complex medical care is far more common than highly standardized procedures like CPR or isolated medical interventions.[35] Our findings suggest that under controlled simulation conditions, complex prehospital care by experienced physicians may be relatively resilient to acute exposure to 3,450 m. However, this should not be interpreted as evidence that all task domains are equally unaffected, particularly those involving sustained physical effort or fine motor skills.\\u003c/p\\u003e \\u003cp\\u003eAn important consideration is the use of a novel composite primary outcome combining medical and non-technical performance. Although all three component instruments (STAT, CALM, and TEAM) are externally validated[27\\u0026ndash;32], the weighting of these components within a single composite score was determined a priori by the investigators and remains partly subjective. This may limit interpretability of the absolute composite score and introduces uncertainty regarding the relative contribution of medical versus non-technical domains to the overall result. Reassuringly, all three components showed a similar directional pattern across conditions, but the composite should nevertheless be regarded as a pragmatic study-specific outcome rather than a universally established measure of care quality.\\u003c/p\\u003e \\u003cp\\u003eInterrater reliability was moderate for the non-technical skill instruments and higher for the medical performance instrument. This may have reduced the sensitivity of the composite score to detect subtle altitude-related differences, especially in communication and leadership domains. Accordingly, a small true effect of altitude on overall performance cannot be ruled out.\\u003c/p\\u003e \\u003cp\\u003eSupplemental oxygen improved oxygen saturation and appeared to attenuate the decline in processing speed (as measured by the DSST), but it was not associated with improved overall simulation performance. This may indicate that the degree of cognitive impairment induced by 3,450 m in this cohort was insufficient to translate into measurable reductions in global care quality, or that the study was underpowered to detect small performance effects. The findings therefore do not support a clear performance benefit of routine supplemental oxygen at this altitude under the present study conditions, but they do not exclude smaller benefits in other settings or at greater altitude. This is in line with the recent recommendations of the International Commission for Mountain Emergency Medicine and the International Society for Mountain Medicine advising the use of supplemental oxygen for all unacclimatized rescue personnel operating at above 3,500 m for longer than 30 min.[36]\\u003c/p\\u003e \\u003cp\\u003eIn this study, medical performance improved after 20 hours at 3,450 m. However, we consider acclimatization processes unlikely to explain this finding. Acclimatization is gradual, with SpO\\u003csub\\u003e2\\u003c/sub\\u003e typically increasing by about 1% per day at this altitude[37], and AMS symptoms peaking after the first night before subsiding.[8] This pattern aligns with our observations: neither SpO\\u003csub\\u003e2\\u003c/sub\\u003e nor AMS scores had markedly improved after 20 hours at 3,450 m. Thus, the observed improvement in performance after 20 hours at altitude compared with acute exposure may reflect a combination of other unmeasured factors\\u0026mdash;such as psychological or social adaptation\\u0026mdash;rather than physiological acclimatization alone.\\u003c/p\\u003e \\u003cp\\u003eIn our exploratory adjusted analyses, greater prehospital experience was associated with better performance during acute altitude exposure. This finding is clinically plausible, as experienced clinicians may rely more effectively on structured routines, pattern recognition, and team management strategies under physiologic stress.[38\\u0026ndash;41] Less experienced physicians may have perceived the simulated cases as more novel and complex, making their performance more vulnerable to altitude-related impairments. This observation is consistent with findings in aviation research.[42,43] However, given the small sample size and the exploratory nature of these models, this association should be interpreted cautiously and regarded as hypothesis-generating rather than confirmatory.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec23\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eLimitations\\u003c/h2\\u003e \\u003cp\\u003eThis study has several limitations. First, despite efforts to maximize realism, simulation cannot fully reproduce the psychological stress, environmental complexity, and operational constraints of real high-altitude emergency missions. The scenarios were short, conducted indoors, and did not include major cold exposure, difficult terrain, or prolonged physical exertion. The observed results may therefore overestimate performance compared with real field conditions.\\u003c/p\\u003e \\u003cp\\u003eSecond, the final analysis included 17 participants, and the study was not designed as a non-inferiority trial. Consequently, the absence of a statistically significant difference between acute altitude exposure and baseline should not be interpreted as proof of equivalence. Small but clinically relevant decrements in performance remain possible within the reported confidence intervals.\\u003c/p\\u003e \\u003cp\\u003eThird, the primary outcome was a study-specific composite score derived from validated component instruments[27\\u0026ndash;32], but the weighting of its components was investigator-defined and therefore partly subjective. In addition, interrater reliability was only moderate for two of the three component instruments, which may have reduced sensitivity for subtle between-condition differences.\\u003c/p\\u003e \\u003cp\\u003eFourth, the exploratory regression analyses should be interpreted with caution given the small sample size, the number of covariates considered, and the absence of adjustment for multiplicity.\\u003c/p\\u003e \\u003cp\\u003eFinally, generalizability may be limited to relatively experienced physician-staffed EMS systems and to altitude exposure around 3,450 m. The findings may not generalize to less experienced providers, longer missions, harsher alpine environments, or substantially greater altitude.\\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"Conclusion\",\"content\":\"\\u003cp\\u003eIn this assessor-blinded simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in overall simulated prehospital emergency care among non-acclimatized EMS physicians. However, because the study was not designed to test non-inferiority, small clinically relevant decrements cannot be excluded. Supplemental oxygen did not improve overall performance under the present study conditions.\\u003c/p\\u003e\"},{\"header\":\"Abbreviations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eAMS\\u003c/strong\\u003e: Acute mountain sickness\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eBART\\u003c/strong\\u003e: Balloon Analog Risk Test\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCALM\\u003c/strong\\u003e: Concise Assessment of Leader Management\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCI\\u003c/strong\\u003e: Confidence interval\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCPR\\u003c/strong\\u003e: Cardiopulmonary resuscitation\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDSST\\u003c/strong\\u003e: Digit-Symbol Substitution Task\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eECG\\u003c/strong\\u003e: Electrocardiogram\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eEMS\\u003c/strong\\u003e: Emergency Medical Services\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eGLMM\\u003c/strong\\u003e: Generalized linear mixed model\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eHEMS\\u003c/strong\\u003e: Helicopter Emergency Medical Services\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eHFSJG\\u003c/strong\\u003e: High Altitude Research Stations Jungfraujoch and Gornergrat\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eICC\\u003c/strong\\u003e: Intraclass correlation coefficient\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eIQR\\u003c/strong\\u003e: Interquartile range\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eLLS\\u003c/strong\\u003e: Lake Louise Score\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eNACA\\u003c/strong\\u003e: National Advisory Committee for Aeronautics\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003ePVT\\u003c/strong\\u003e: Psychomotor Vigilance Task\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eSpO\\u003csub\\u003e2\\u003c/sub\\u003e\\u003c/strong\\u003e: Peripheral oxygen saturation\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eSTAT\\u003c/strong\\u003e: Simulation Team Assessment Tool\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eTEAM\\u003c/strong\\u003e: Team Emergency Assessment Measure\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eVAS\\u003c/strong\\u003e: Visual analogue scale\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eEthics approval and consent to participate\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eEthical approval for this study was provided by the Cantonal Research Ethics Committee Bern, Switzerland (Chairperson Prof. Christian Seiler) on 8 July 2024 (ID: 2024-00237). Written informed consent was obtained from all participants. All study procedures were conducted in accordance with the Declaration of Helsinki.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConsent for publication\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eNot applicable.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAvailability of data and materials\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe deidentified datasets generated and/or analysed during the current study are not publicly available due to data protection considerations but are available from the corresponding author on reasonable request. Any custom-made code used in this study and the detailed trial protocol and statistical analysis plan are likewise available from the corresponding author on reasonable request.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCompeting interests\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors declare that they have no competing interests.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFunding\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eSven Straumann was supported by a Young Investigator Grant from the Clinical Trial Unit, University Hospital Bern, awarded specifically for this study. Additional financial support was provided by the Department of Anaesthesiology and Pain Medicine, University Hospital Bern.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eJ\\u0026uuml;rgen Knapp received ongoing protected research time funded by Swiss Air Rescue REGA, Zurich. The funding bodies had no role in the design of the study, collection, analysis, and interpretation of data, or in writing the manuscript.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAuthors\\u0026rsquo; contributions\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eSS, JK, and MMB conceived the study, designed the trial, and obtained research funding. SS and JK obtained ethical approval. SS recruited participants. SS and JK supervised study conduct, data collection, data management, and quality control. SS, JK, ACZ, and LAW were directly involved in data collection. TH, FU, and FCF served as blinded outcome assessors. SS and MH provided statistical advice on study design and analysed the data. SS drafted the manuscript, and all authors contributed substantially to its revision. SS takes responsibility for the paper as a whole. All authors read and approved the final manuscript.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAcknowledgements\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors would like to thank Yves Balmer and Peter Hinderberger of the Bern Simulation and CPR Center (BeSiC), as well as the High Altitude Research Stations Jungfraujoch and Gornergrat (HFSJG), for their invaluable support in conducting this study.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\n\\u003cli\\u003eMaddock A, Corfield AR, Donald MJ, Lyon RM, Sinclair N, Fitzpatrick D, et al. Prehospital critical care is associated with increased survival in adult trauma patients in Scotland. \\u003cem\\u003eEmerg Med J \\u003c/em\\u003e2020; \\u003cstrong\\u003e37\\u003c/strong\\u003e (3):141-145.\\u003c/li\\u003e\\n\\u003cli\\u003eKnapp J, Haske D, Bottiger BW, Limacher A, Stalder O, Schmid A, et al. 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Incidence and challenges of helicopter emergency medical service (HEMS) rescue missions with helicopter hoist operations: analysis of 11,228 daytime and nighttime missions in Switzerland. \\u003cem\\u003eScand J Trauma Resusc Emerg Med \\u003c/em\\u003e2021; \\u003cstrong\\u003e29\\u003c/strong\\u003e (1):92.\\u003c/li\\u003e\\n\\u003cli\\u003eMcLaughlin K, Roy S, Falla M, Strapazzon G, Luks AM, Zafren K, et al. Pharmacological Prophylaxis and Supplemental Oxygen for Unacclimatized Rescuers at Very High Altitude: Scoping Review and 2025 Joint Recommendations of the International Commission for Mountain Emergency Medicine and the International Society for Mountain Medicine. \\u003cem\\u003eHigh Alt Med Biol \\u003c/em\\u003e2026; \\u003cstrong\\u003e27\\u003c/strong\\u003e (1):60-77.\\u003c/li\\u003e\\n\\u003cli\\u003eDunnwald T, Kienast R, Niederseer D, Burtscher M. The Use of Pulse Oximetry in the Assessment of Acclimatization to High Altitude. \\u003cem\\u003eSensors (Basel) \\u003c/em\\u003e2021; \\u003cstrong\\u003e21\\u003c/strong\\u003e (4).\\u003c/li\\u003e\\n\\u003cli\\u003eBuljac-Samardzic M, Dekker-van Doorn CM, Maynard MT. What Do We Really Know About Crew Resource Management in Healthcare?: An Umbrella Review on Crew Resource Management and Its Effectiveness. \\u003cem\\u003eJ Patient Saf \\u003c/em\\u003e2021; \\u003cstrong\\u003e17\\u003c/strong\\u003e (8):e929-e958.\\u003c/li\\u003e\\n\\u003cli\\u003eDijkstra FS, Renden PG, Meeter M, Schoonmade LJ, Krage R, van Schuppen H, et al. Learning about stress from building, drilling and flying: a scoping review on team performance and stress in non-medical fields. \\u003cem\\u003eScand J Trauma Resusc Emerg Med \\u003c/em\\u003e2021; \\u003cstrong\\u003e29\\u003c/strong\\u003e (1):52.\\u003c/li\\u003e\\n\\u003cli\\u003eMuller MP, Hansel M, Fichtner A, Hardt F, Weber S, Kirschbaum C, et al. Excellence in performance and stress reduction during two different full scale simulator training courses: a pilot study. \\u003cem\\u003eResuscitation \\u003c/em\\u003e2009; \\u003cstrong\\u003e80\\u003c/strong\\u003e (8):919-924.\\u003c/li\\u003e\\n\\u003cli\\u003eThim T, Krarup NH, Grove EL, Rohde CV, Lofgren B. Initial assessment and treatment with the Airway, Breathing, Circulation, Disability, Exposure (ABCDE) approach. \\u003cem\\u003eInt J Gen Med \\u003c/em\\u003e2012; \\u003cstrong\\u003e5\\u003c/strong\\u003e:117-121.\\u003c/li\\u003e\\n\\u003cli\\u003eBouak F, Vartanian O, Hofer K, Cheung B. Acute Mild Hypoxic Hypoxia Effects on Cognitive and Simulated Aircraft Pilot Performance. \\u003cem\\u003eAerosp Med Hum Perform \\u003c/em\\u003e2018; \\u003cstrong\\u003e89\\u003c/strong\\u003e (6):526-535.\\u003c/li\\u003e\\n\\u003cli\\u003eKryskow MA, Beidleman BA, Fulco CS, Muza SR. Performance during simple and complex military psychomotor tasks at various altitudes. \\u003cem\\u003eAviat Space Environ Med \\u003c/em\\u003e2013; \\u003cstrong\\u003e84\\u003c/strong\\u003e (11):1147-1152.\\u003c/li\\u003e\\n\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"hideJournal\":false,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scandinavian-journal-of-trauma-resuscitation-and-emergency-medicine\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"stre\",\"sideBox\":\"Learn more about [Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine](http://sjtrem.biomedcentral.com)\",\"snPcode\":\"13049\",\"submissionUrl\":\"https://submission.nature.com/new-submission/13049/3\",\"title\":\"Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine\",\"twitterHandle\":\"@SJTREM\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"BMC/SO AJ\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true},\"keywords\":\"High altitude, hypobaric hypoxia, prehospital emergency care, emergency medical services (EMS), supplemental oxygen, medical performance\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-9268709/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-9268709/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003e\\u003cstrong\\u003eBackground: \\u003c/strong\\u003eHigh-altitude rescue operations expose Emergency Medical Services (EMS) teams to hypobaric hypoxia, which may impair cognition and team performance. However, its effect on the overall quality of prehospital emergency care remains unclear. We aimed to assess whether acute exposure to high altitude (3,450 m) is associated with reduced quality of simulated prehospital emergency medical care delivered by non-acclimatized EMS physicians.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eMethods\\u003c/strong\\u003e: We conducted an assessor-blinded, randomized crossover simulation study in Switzerland between September 2024 and January 2025, in which 20 non-acclimatized EMS physicians managed simulated emergency scenarios under four conditions in randomized order: baseline at low altitude (540 m), acute exposure to high altitude (3,450 m), acute exposure to 3,450 m with supplemental oxygen at 4 L/min, and after 20 hours at 3,450 m. Video-recorded performances were independently assessed by three blinded experts using validated instruments for medical and non-technical performance. The primary outcome was a composite score comprising 50% medical and 50% non-technical skills. Seventeen participants completed all four scenarios and were included in the primary analysis.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eResults: \\u003c/strong\\u003eMedian [IQR] composite performance was 82% [76–83] at baseline, 74% [70–83] during acute exposure to 3,450 m, 82% [68–83] with supplemental oxygen, and 83% [77–86] after 20 hours at altitude. In generalized linear mixed modelling, overall composite performance did not differ significantly across the four conditions (P=0.082). Performance during acute altitude exposure (C2) did not differ significantly from baseline (C1) (-1%, 95% CI -5% to 3%; P=0.53). Supplemental oxygen (C3) did not improve performance compared with C2 (0%, 95% CI -4% to 4%; P=0.94), whereas performance after 20 hours at altitude (C4) was higher than at C2 (5%, 95% CI 1% to 9%; P=0.03). In exploratory adjusted analyses, greater prehospital experience was associated with better performance during acute altitude exposure.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConclusions:\\u003c/strong\\u003e In this assessor-blinded simulation study, acute exposure to 3,450 m was not associated with a statistically significant reduction in overall simulated prehospital emergency care among non-acclimatized EMS physicians. However, the confidence intervals do not exclude small clinically relevant decrements. Supplemental oxygen did not improve overall performance under these study conditions.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eTrial registration\\u003c/strong\\u003e: ClinicalTrials.gov NCT06446427\\u003c/p\\u003e\",\"manuscriptTitle\":\"Quality of prehospital emergency care at high altitude: a randomized assessor-blinded simulation crossover study\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2026-04-19 07:57:05\",\"doi\":\"10.21203/rs.3.rs-9268709/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2026-05-13T21:37:12+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"174638676333634927695531203612926890571\",\"date\":\"2026-04-28T20:27:29+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2026-04-20T23:20:04+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"103459250853909792074509476291362175026\",\"date\":\"2026-04-10T15:52:47+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2026-04-08T14:14:26+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2026-04-01T02:39:18+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2026-04-01T02:38:20+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine\",\"date\":\"2026-03-30T14:39:27+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scandinavian-journal-of-trauma-resuscitation-and-emergency-medicine\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"stre\",\"sideBox\":\"Learn more about [Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine](http://sjtrem.biomedcentral.com)\",\"snPcode\":\"13049\",\"submissionUrl\":\"https://submission.nature.com/new-submission/13049/3\",\"title\":\"Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine\",\"twitterHandle\":\"@SJTREM\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"BMC/SO AJ\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"ee7bb866-b9b9-4869-8eb4-b4b9a1965a46\",\"owner\":[],\"postedDate\":\"April 19th, 2026\",\"published\":true,\"recentEditorialEvents\":[{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2026-05-13T21:37:12+00:00\",\"index\":21,\"fulltext\":\"\"}],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"under-review\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2026-04-19T07:57:05+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2026-04-19 07:57:05\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-9268709\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-9268709\",\"identity\":\"rs-9268709\",\"version\":[\"v1\"]},\"buildId\":\"XKTyCvWXoU3ODBz1xrDgd\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}