Redefining trauma deserts: novel technique to accurately map prehospital transport time.

Background: Prehospital transport time has been directly related to mortality for hemorrhaging trauma patients. 'Trauma deserts' were previously defined as being outside of a 5-mile radial distance of an urban trauma center. We postulated that the true 'desert' should be based on transport time rather than transport distance. Methods: Using the Chicagoland area that was used to describe 'trauma deserts,' a sequential process to query a commercial travel optimization product to map transport times over coordinates that covered the entire urban area at a particular time of day. This produces a heat map representing prehospital transport times. Travel times were then limited to 15 minutes to represent a temporally based map of transport capabilities. This was repeated during high and low traffic times and for centers across the city. Results: We demonstrated that the temporally based map for transport to a trauma center in an urban center differs significantly from the radial distance to the trauma center. Primary effects were proximity to highways and the downtown area. Transportation to centers were significantly different when time was considered instead of distance (p<0.001). We were further able to map variations in traffic patterns and thus transport times by time of day. The truly 'closest' trauma center by time changed based on time of day and was not always the closest hospital by distance. Discussion: As the crow flies is not how the ambulance drives. This novel technique of dynamically mapping transport times can be used to create accurate trauma deserts in an urban setting with multiple trauma centers. Further, this technique can be used to quantify the potential benefit or detriment of adding or removing firehouses or trauma centers.