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Logistics of air medical transport

When and where does helicopter transport reduce prehospital time for trauma?

Chen, Xilin, MPH; Gestring, Mark L., MD; Rosengart, Matthew R., MD, MPH; Peitzman, Andrew B., MD; Billiar, Timothy R., MD; Sperry, Jason L., MD, MPH; Brown, Joshua B., MD, MSc

Journal of Trauma and Acute Care Surgery: July 2018 - Volume 85 - Issue 1 - p 174–181
doi: 10.1097/TA.0000000000001935
EAST Quickshot Presentations

BACKGROUND Trauma is a time sensitive disease. Helicopter emergency medical services (HEMS) have shown benefit over ground emergency medical services (GEMS), which may be related to reduced prehospital time. The distance at which this time benefit emerges depends on many factors that can vary across regions. Our objective was to determine the threshold distance at which HEMS has shorter prehospital time than GEMS under different conditions.

METHODS Patients in the Pennsylvania trauma registry 2000 to 2013 were included. Distance between zip centroid and trauma center was calculated using straight-line distance for HEMS and driving distance from geographic information systems network analysis for GEMS. Contrast margins from linear regression identified the threshold distance at which HEMS had a significantly lower prehospital time than GEMS, indicated by nonoverlapping 95% confidence intervals. The effect of peak traffic times and adverse weather on the threshold distance was evaluated. Geographic effects across EMS regions were also evaluated.

RESULTS A total of 144,741 patients were included with 19% transported by HEMS. Overall, HEMS became faster than GEMS at 7.7 miles from the trauma center (p = 0.043). Helicopter emergency medical services became faster at 6.5 miles during peak traffic (p = 0.025) compared with 7.9 miles during off-peak traffic (p = 0.048). Adverse weather increased the distance at which HEMS was faster to 17.1 miles (p = 0.046) from 7.3 miles in clear weather (p = 0.036). Significant variation occurred across EMS regions, with threshold distances ranging from 5.4 to 35.3 miles. There was an inverse but non-significant relationship between urban population and threshold distance across EMS regions (ρ, −0.351, p = 0.28).

CONCLUSION This is the first study to demonstrate that traffic, weather, and geographic region significantly impact the threshold distance at which HEMS are faster than GEMS. Helicopter emergency medical services was faster at shorter distances during peak traffic while adverse weather increased this distance. The threshold distance varied widely across geographic region. These factors must be considered to guide appropriate HEMS triage protocols.

LEVEL OF EVIDENCE Therapeutic, level IV.

From the Division of Trauma and General Surgery, Department of Surgery (X.C., M.R.R., A.B.P., T.R.B., J.L.S., J.B.B.), University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; and Division of Acute Care Surgery, Department of Surgery (M.G.L.), University of Rochester Medical Center, Rochester, New York.

Submitted: November 29, 2017, Revised: January 20, 2018, Accepted: March 25, 2018, Published online: May 4, 2018.

This article was presented as a quick shot presentation at the 31st Annual Scientific Assembly of the Eastern Association for the Surgery of Trauma, January 9–13th, 2018; Lake Buena Vista, FL.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (

Address for reprints: Joshua B. Brown, MD, Division of Trauma and General Surgery, Department of Surgery, University of Pittsburgh Medical Center 200 Lothrop Street, Pittsburgh, PA 15213; email:

© 2018 Lippincott Williams & Wilkins, Inc.