In Japan, Emergency Life-Saving Technicians (ELSTs) cannot independently perform diagnostic ultrasound under the current legal framework. If ELST-performed focused assessment with sonography for trauma (FAST) is to be introduced in the prehospital setting, technical feasibility during ambulance motion and the viability of remote physician observation must be established.

The study aimed to evaluate the feasibility of ELST-performed FAST in moving ambulances in a controlled manikin setting and to descriptively assess an integrated monitoring system for remote observation.

A prospective observational pilot study was conducted at the Okayama City Fire Department Training Center in Okayama Prefecture, Japan on March 3, 2025. Twenty ELSTs completed structured e-learning and a hands-on workshop using standardized FAST/ER FAN manikins. Participants performed FAST under three fixed-order conditions: stationary (STOP), 15km/hour, and 30km/hour on a 250-m circular course. The primary outcome was the total Task-Specific Checklist (TSC) score (0-24 points). Secondary outcomes were examination time, site-specific TSC subscores, inter-rater agreement, and a descriptive assessment of transmitted image quality by two specialist physicians.

All 20 ELSTs completed the study. Mean total TSC scores were 23.4 (SD = 0.8) in the STOP condition, 23.4 (SD = 0.9) at 15km/hour, and 23.7 (SD = 0.6) at 30km/hour. Compared with the STOP condition, the mean difference in total TSC score was 0.08 points (95% CI, −0.24 to 0.39; P for noninferiority < 0.001) at 15km/hour and 0.33 points (95% CI, −0.04 to 0.69; P for noninferiority < 0.001) at 30km/hour. Both moving conditions met the pre-specified noninferiority criterion relative to the STOP condition. Mean examination times were 36.7 (SD = 14.4) seconds in the STOP condition, 30.3 (SD = 9.8) seconds at 15km/hour, and 31.9 (SD = 14.8) seconds at 30km/hour. Inter-rater agreement for TSC scoring was moderate (weighted kappa, 0.56). Descriptive ratings suggested that transmitted image quality was generally favorable for remote review in this controlled setting.

In this controlled manikin-based pilot study, ELST-performed FAST was technically feasible during moderate ambulance motion, and remote physician observation was feasible. These findings may help inform staged prehospital ultrasound training and future clinical validation under legal and operational constraints.

Out-of-hospital cardiac arrest (OHCA) is a significant global cause of mortality, and Emergency Medical Services (EMS) response interval is critical for survival and a neurologically-favorable outcome. Currently, it is unclear whether EMS response interval, neurologically-intact survival, and overall survival differ between snowy and non-snowy periods at heavy snowfall areas.

A nation-wide population-based cohort of OHCA patients, registered from 2017 through 2019 in the All-Japan Utstein Registry, was divided into four groups according to areas (heavy snowfall area or other area) and seasons (winter or non-winter): heavy snowfall-winter, heavy snowfall-non-winter, other area-winter, and other area-non-winter. The first coprimary outcome was EMS response interval, and the secondary coprimary outcome was one-month survival and a neurologically-favorable outcome at one month.

A total of 337,781 OHCA patients were divided into four groups: heavy snowfall-winter (N = 15,627), heavy snowfall-non-winter (N = 97,441), other area-winter (N = 32,955), and other area-non-winter (N = 191,758). Longer EMS response intervals (>13 minutes) were most likely in the heavy snowfall-winter group (OR = 1.86; 95% CI, 1.76 to 1.97), and also more likely in heavy snowfall areas in non-winter (OR = 1.44; 95% CI, 1.38 to 1.50). One-month survival in winter was worse not only in the heavy snowfall area (OR = 0.86; 95% CI, 0.78 to 0.94) but also in other areas (OR = 0.91; 95% CI, 0.87 to 0.94). One-month neurologically-favorable outcomes were also comparable between heavy snowfall-winter and other area-non-winter groups.

This study showed OHCA in heavy snowfall areas in winter resulted in longer EMS response intervals. However, heavy snowfall had little effect on one-month survival or neurologically-favorable outcome at one month.