In our results, the average time required by HEMS was 61 minutes, which was 56 minutes shorter compared to that required by GEMS. Further, we successfully secured ideal linear curves for the two transportation systems (between distance and time required). By using the curves and exact injury point and destination addresses, we can finally calculate the time saved, which can be a good reference for making a decision on the transportation modality.
HEMS was originally used as air transport in military evacuation during the Korean War, and its use in civilian situations was initiated in the 1960s in the United States.[18, 19] Since then, the HEMS has been successfully utilized in the transportation of injured victims to trauma centers in several advanced countries (especially those with broad territories), and the role of air transportation in long distances, hostile environments, and difficult geographical areas that cannot be accessed by ground ambulances has been undisputed.[14] However, the setting for HEMS requires a great deal of human as well as other fundamental resources after social agreements. Further, the effectiveness of HEMS remains controversial, such as in countries with small territories with good ground traffic conditions.[7, 9, 15, 19] Several studies have highlighted the importance of reducing the helicopter transportation of near-hospital injuries and over-triage of minor injury patients for air transportation in order to achieve better cost-effectiveness and practical mortality or disability reductions in HEMS.[7, 8, 20]
In South Korea, 17 regional trauma centers have been evenly distributed across the country for the provision of superior medical services to patients with emergent and traumatic diseases. In these centers, several efforts have been made to utilize helicopter transport including a pilot project referred to as “Doctor Heli 2011”;[12] however, HEMS failed to be set-up such that only 237 patients of a total of 139,072 major medical emergency patients were airlifted by helicopters (0.001%).[21] This might be related to the poor fundamental support from the government and insufficient social understanding that cost-effectiveness cannot be fully achieved due to the geographic characteristics of South Korea (small territory, high urban population density, and excellent road-traffic networks). Currently, HEMS is only operated in four institutions, and a nationwide expansion of the service is mandatory.
In contrast, in 2015, the MEOC set up a military HEMS and managed every case of emergency notification. From 2015 to 2019, a total of 573 patients were notified of their transportation from camps (or initial frontline medical facilities) to a suitable emergency center by HEMS. A relatively large volume of helicopter transportation is available in a single command (compared to the total number of regional trauma centers) as the military HEMS can be fully equipped, as covered by the Ministry of National Defense budget. Furthermore, since military corps are usually located on the frontlines that are far from urban areas, the distance from the injury point to the hospital makes it suitable to utilize HEMS. To date, the MEOC directly offers HEMS for military medical welfare as well as preparation for handling a potential mass casualty situation due to injuries that occur during wartime combat. In addition, as the MEOC does not pursue profits from the utilization of HEMS, a comparison between the two modalities can be objectively conducted. Here, we compared the two transportation modalities (helicopter vs. ground ambulance) and identified several different characteristics.
First, both types of transportation can be started simultaneously (after notification); however, the starting points are different in that a ground ambulance is usually directly available from the injury point, whereas a helicopter should move from the command to the injury point to begin patient transportation. Therefore, each transportation has a completely different route. As shown in Fig. 1, helicopters usually need additional transfer, indicated as “H1”; however, H2 can be shortened by using an air route. On the other hand, if ground transportation has to be used in this case, then the transportation directly starts by using G2, which is dependent on the road condition and traffic situation. However, the majority of previous studies have compared two modalities by considering different patient groups.[14, 15, 22, 23] This might induce a significant heterogeneity between the groups, and objective comparison cannot be secured. By using a navigation software, we obtained each patient’s “practically used airline route” and “predicted ground traffic route,” and finally, the groups indicated a similar range of distance without any significance (p = 0.3021, Fig. 4A).
Second, the practical HEMS pre-hospital time was significantly shorter than the predicted GEMS pre-hospital time (Fig. 4A, p < 0.0001). It is clear that approximately 56 minutes can be saved by using HEMS when the injury points are located on an average of 120 kilometers (or 116 minutes) far from the hospital. Beyond controversies, the “golden hour” is a well-known lexicon among trauma surgeons and EMS providers, and the underlying tenet of this adage suggests an injured patient has 60 minutes to receive definitive care from time of injury, after which chances of morbidity and mortality significantly increase.[3, 24, 25] In our results, HEMS can enable the injured patients who are in over one-hour distances from hospital to arrive at the emergency centers within the “golden hour.”
Third, both types of transportation are significantly associated with a simple linear curve, but the slope of the graphs differ (0.2739 of HEMS vs. 0.5483 in GEMS, Fig. 5). It can be interpreted that the average HEMS speed is twice as fast as that of GEMS. The greater the distance from the hospital, the more the time that can be saved. As mentioned, only a few studies that compare the slope or curves (between distance and time) of the modalities have been reported,[22, 26] and to the best of our knowledge, the current result is the first curve in Korean HEMS circumstances. Furthermore, the R2 parameter, which refers to the goodness-of-fit of the ideal curve, is higher in HEMS (0.7722 in HEMS vs. 0.6518 in GEMS).[27] It may be inferred that the HEMS is accompanied by a lower possibility of transportation delays and is less dependent on unpredictable interfering factors. Beyond the controversies on cost-effectiveness, HEMS can be regarded as an ideal “predictable” transfer modality for patients who are in over an-hour distances.
In fact, we failed to secure the ultimate curve for the time saved as it was not significant and displayed poor R2 parameters (Fig. 6). As the two modalities have totally different routes and consequent curves, they cannot be easily integrated into one simple curve. Instead, by using two curves, we can assess the time saved, which is the final value for a physician to use when deciding on the transportation modality. The HEMS graph (Fig. 5A) has both significance and goodness-of-fit; it can be used as the basic curve for Korean HEMS circumference of Gyeonggi-Gangwon province. By combining it with the social navigation software, each transportation time can be minutely analyzed. A future development of a software or application may provide wide accessibility for EMS-involved persons such as physicians, emergency medical technicians, and EMS providers.
The current study has several limitations. First, cost-effectiveness was not analyzed. Because of the distinct characteristics of military medicine, the HEMS can be utilized without considering the operating profits. A comparison of budgets between HEMS and GEMS can be a good reference for policymakers. Second, patient factors, including the severity of injury and outcomes, were not included. The analyses were based on the documentation from MEOC, which precisely recorded the information on “helicopter transportation,” including the injury point address and destination, and each time required. The detailed patient information could only be assessed after reviewing each destination hospitals’ medical records, which were not included in this study. Third, the results or graphs of the current study cannot be generalized since the road traffic condition and hospital distribution may differ among the provinces and/or countries. However, the flatform of the study can be easily adapted to other situations using retrospective data and navigation software.