Quality of prehospital emergency care at high altitude (3,450 m) by non-acclimatised EMS physicians: a randomised assessor-blinded simulation crossover study

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, randomised crossover simulation study in Switzerland between September 2024 and January 2025, in which 20 non-acclimatised EMS physicians managed simulated emergency scenarios under four conditions: 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 prespecified composite score comprising 50% medical and 50% non-technical skills, with individual component scores as secondary outcomes. 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 experienced, non-acclimatised 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