introduced by cowley in the 1970s , the  golden hour  concept has since governed planning and preparedness in trauma systems development as a major source of morbidity and mortality to the population that contributes to the economy , i.e. , people less than 45 years of age , trauma is a significant problem that needs continuous systems improvement . an integrated trauma system improves outcomes for patients of trauma , but the exact parameters that determine effectiveness have yet to be conclusively defined . the relationship between shortened pre - hospital time and improved survival exists , but is most consistently demonstrated when comparing urban and rural locals . no data exists that specifically quantifies the relationship between pre - hospital time and outcomes within purely urban areas , and especially in patients sustaining penetrating trauma . these patients are most likely to benefit from expedited transport if definitive surgical management is required . current literature has failed to study the association between pre - hospital transport time and survival for penetrating trauma patients . the studies that have examined the urban setting have yielded contradictory conclusions ; sloan and petri in chicago evaluated blunt and penetrating trauma patients and did not find a relationship between transport time and outcome . pepe in houston assessed hypotensive patients with penetrating trauma and was unable to demonstrate any relationship . gervin and feero , on the other hand , demonstrated that shorter pre - hospital time improved survival . the contradictory results may be secondary to the heterogeneity of the trauma patient population at different locations . trauma centers in many high - volume locations do not have significant number of penetrating trauma patients . this begs further investigation to define the influence of pre - hospital time factors on trauma outcomes in urban environments and in particular , in patients with penetrating trauma . our study explores the impact of pre - hospital times on penetrating trauma outcomes within urban centers of illinois . we hypothesized that there would be a relationship between total pre - hospital time and outcomes in patients with penetrating thoracic trauma , an injury that is potentially lethal without emergent intervention . since injury severity is strongly associated with mortality , we specifically studied the patients at highest risk , hypotensive patients who would be most likely to have hemorrhage that would benefit from rapid surgical control . this registry contains data from all traumatically injured patients brought to the 67 level i and level ii trauma centers in illinois . the data are entered by a registrar at each trauma center and uploaded to the illinois department of public health , who maintains the data set and website . not included in this registry are patients who are declared dead - on - scene and not transported to a trauma center and patients not treated at or transferred to a level i or level ii trauma center . the emergency medical system ( ems ) in illinois is a tiered system with paramedics trained in both basic life support and advanced life support techniques . the chicago committee on trauma works with the state of illinois and pre - hospital providers to ensure safe , standardized care and undergoes rigorous quality improvement scrutiny . the illinois state trauma registry ( istr ) includes approximately 45,000 records per year . to limit our study to urban trauma patients , we selected patients of all ages injured in the major urban areas of chicago , east st . louis , and springfield ( more than 2/3 of cases annually ) . because our question of interest was the effect of transport time on mortality , we excluded all transfer patients , as well as walk - in and self - transport patients ( 10% of cases annually ) . we identified patients with penetrating injuries using information regarding the primary mechanism of injury recorded in the database ( approximately 2,500 cases per year ) and then classified those patients with thoracic trauma using icd-9 cm codes . the final list of icd-9 codes was limited to penetrating thoracic injuries ( codes 860 - 862 , approximately 150 cases per year ) , consistent with the center for medicaid and medicare services ( cms ) designations . the pre - hospital vital sign data were poorly conserved with fifty percent missing ; for that reason , hypotension  was defined as a systolic blood pressure ( sbp ) less than 90 mmhg on the first reading in the emergency department . total pre - hospital time consisted of response time , scene time , and transport time . each of these variables was evaluated separately and in aggregate as total pre - hospital time . student 's t - test was used as the test statistic for the comparisons of mean pre - hospital time between cohorts . the injury severity score ( iss ) was used as an anatomic marker of injury severity and was highly conserved in the data set ( < 3% missing data ) . a two - sample test of proportions and pearson 's chi - squared test were used to compare survival among patients with iss < 16 and 16 and total pre - hospital time . logistic regression statistics were performed to determine the independent effect of transport time on mortality when controlling for age , race , and severity of injury for both hypotensive patients with penetrating thoracic injuries ( hpti ) and non - hypotensive patients with penetrating thoracic injuries ( npti ) . for the models , transport times were categorized into 15 min intervals to determine the independent effect of successively longer transport times . a total of 908 patients with penetrating thoracic injuries ( pti)were evaluated during the study period . one - hundred forty - three patients ( 16% ) were hypotensive on presentation , with a systolic blood pressure less than 90mmhg ( hypotensive pti group = hpti ) , while 765 patients ( 84% ) had systolic blood pressures greater than 90 mmhg ( normotensive pti group = npti ) . the mean age was approximately 27 years ( age range 11 - 78 , 99% between ages 15 and 55 ) and the majority of patients were african american , male and uninsured [ table 1 ] . thirty percent ( 230 ) of npti patients had an iss greater than 16 , while 55% ( 79 ) of hpti patients had an iss greater than 16 ( p < 0.001 ) . the time for paramedics to get to the scene ( mean response time , 4.5 min vs. 5.4 , p = 0.05 ) , mean transport time ( 8.9 min vs. 11.2 , p = 0.02 ) and total pre - hospital time ( 25.67 vs. 29.47 , p = 0.02 ) were significantly shorter for hpti patients with an iss  16 compared to hpti patients with iss < 16 . however , mean scene times did not differ ( p = 0.64 ) [ table 2 ] . injury severity and transport times , bivariate statistics crude mortality was higher for hpti patients compared with npti patients ( 73% vs. 12% , p < 0.001 ) . hypotensive patients with penetrating thoracic injuries ( hpti ) patients showed increased mortality with increased total pre - hospital time [ figure 1 ] . the odds ratio ( or ) of death for hpti patients , similarly , increased with increasing total pre - hospital time [ table 3 , figure 2 ] . for instance , if pre - hospital time was greater than 40 min , then the or was increased to 13 ( p < 0.001 ) . table 3 reports the regression results for hpti patients . non - hypotensive patients with penetrating thoracic injuries ( npti ) regression results are not included , but the covariates for age , race , gender , and iss were of similar direction and magnitude . conversely , npti patients with longer total pre - hospital times exhibited decreased mortality ( or 0.93 , 95% ci 0.83 - 0.99 , p < 0.001 ) . death ratefor non - hypotensive patients with penetrating thoracic injuries and hypotensive patients with penetrating thoracic injuries patients grouped by pre - hospital time adjusted risk of death for hpti patients by pre - hospital time rr of death for hypotensive patients with penetrating thoracic injuries vs. non - hypotensive patients with penetrating thoracic injuries patients grouped by pre - hospital time of the survivors , the majority of patients , in both npti and hpti groups , were discharged directly to home . there were no significant differences in the discharge destination for ntpi and hpti patients [ table 4 ] . the study investigates association between transport time and outcome for urbanvictims of penetrating thoracic trauma . the analysis indicates that more severely injured patients may survive devastating injuries with rapid transit : the sicker the patient , the quicker they should be in the trauma bay . a significantly positive finding of this study was that patients with higher injury severity experienced shorter pre - hospital transport time . this finding in our study is not unique ; newgard demonstrated this in a multi - institutional study mixed population of blunt and penetrating trauma . given the significant correlation between pre - hospital time and mortality for hpti patients , this is clearly a success of the urban trauma system . the association of transport time with mortality has been well described in rural trauma systems , but never clearly described in the urban setting , with a homogeneous population of patients . this study is one of the first to show a consistent association between pre - hospital time and survival in an urban trauma system with uniform professional pre - hospital ems care . variations in transport times might be due to travel distances to the nearest trauma center from incident scenes , traffic congestion or road conditions , or weather conditions . it is possible with new global positioning systems ( gps ) data that incorporates traffic congestion and travel distances , pre - hospital times may be shortened . some rural trauma systems have augmented their pre - hospital services with aeromedical transporter provided increased trauma training for first responders to decrease the impact of longer transport times on injury mortality . these options might be employed to a greater degree in urban trauma systems as well . however , comprehensive changes in a system that is working well for most patients may not be indicated or cost - effective . it is important to note that our findings are limited to a small portion of all trauma patients : in our database , pti patients comprised approximately 2% of all trauma patients and hpti patients comprised only 0.4% of all trauma patients . it is likely that many , less severely injured will not experience a survival benefit associated with decreased pre - hospital time ; as notably seen in the npti group , in whom survival was not adversely affected by increased transport time , and was actually improved . it is important to recognize that the majority of the overall trauma patient population with penetrating thoracic injuries did not benefit from shorter transport times . in addition , pre - hospital data were missing up to 50% of the time , including sbp . though no systematic changes have occurred in urban pre - hospital transport during that time , additional years of data should be accessed when available to validate these results . despite these limitations , these results suggest that careful planning to optimize transport time - encompassing hospital capacity and existing resources , traffic patterns , and trauma incident densities - may be beneficial in areas with a high burden of penetrating trauma . in conclusion , we have shown that minimizing pre - hospital times does in fact impact survival in patients that are hypotensive victims of penetrating thoracic trauma . hpti patients in an optimally designed trauma system should be delivered to definitive care expeditiously .