Objective: On-scene prehospital conditions and patient instability may warrant a during-transport ultrasound (US) exam. The objective of this study was to assess the effect of ambulance turbulence on the performance of the Focused Assessment with Sonography in Trauma (FAST) with a handheld US device. Methods: This was a randomized controlled trial in which participants were randomized to perform a FAST in either a stationary or an in-motion military ambulance. Participants were physicians and physician assistants (PAs) with previous FAST training. All exams were performed on an US phantom model. The primary outcome was FAST completion time, reported as a mean, in seconds. Secondary outcomes included image acquisition score (range of 0-24, reported as a mean), diagnostic accuracy (reported as sensitivity and specificity), and a post-participation survey with five-item Likert-type scales. Results: Twenty-seven participants performed 27 FASTs, 14 in the stationary ambulance and 13 in the in-motion ambulance. All participants obtained the four requisite views of the FAST. A significant difference was detected in image acquisition scores in favor of the stationary ambulance group (19.4 versus 16.7 [95% CI for difference, 0.9-4.4]; P <.01). Significant differences in survey items between groups were related to obtaining and maintaining US images and the exam conditions. There was not a difference in FAST completion time between groups (98.5 seconds versus 78.7 seconds [95% CI for difference, -13.5 seconds to 53.1 seconds]; P = .23). Sensitivity and specificity of FAST in the stationary ambulance was 85.7% (95% CI, 67.3%-96.0%) and 96.4% (95% CI, 81.7%-99.9%) versus 96.2% (95% CI, 80.4%-99.9%) and 100.0% (95% CI, 86.8%-100.0%) in the in-motion ambulance group (P = .21). Conclusion: Vehicular motion did not affect FAST completion time and diagnostic accuracy; however, it did reduce FAST image acquisition scores. The results suggest timely and diagnostically accurate FASTs may be completed by experienced sonographers during moderate levels of ambulance turbulence. Further investigation assessing the utility and limitations of newer handheld US devices in various prehospital conditions is warranted.

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