Helicopter transport is an integral component of modern trauma systems which, in turn, have been shown to reduce preventable mortality in Australia [1, 19]. However, few studies have investigated the financial implications of such systems, particularly from the perspective of the hospitals that receive trauma patients. Our study aimed to investigate the financial implications of HEMS over-triage from the perspective of the major trauma centre in NSW. In doing so, we have provided the first state-wide description of HEMS patient characteristics and estimates of HEMS over-triage. In addition to previous literature demonstrating the inadequacy of the episode funding model [20–23], our results highlight the implications of episode funding to a major trauma hospital that receives HEMS patients. Specifically, in terms of potential funding discrepancies, over-triaged HEMS patients may be as costly to a trauma centre as correctly triaged patients. Further, the financial impact of receiving HEMS patients varies by the type of transport undertaken (either pre-hospital or inter-hospital).
In many developed countries, HEMS are used to complement existing ground infrastructure. Recent reviews have shown a consistent association between HEMS use and improved patient outcomes in trauma [24, 25]. However, due to the difficulty in accurately determining patient acuity, HEMS patients are frequently over-triaged; resulting in patients being transported who do not require advanced care or expedient transport. Our results demonstrate that HEMS patients in NSW have a high over-triage rate. This is consistent with a meta-analysis of the HEMS literature showed 60% of patients (99% CI: 54.5%-64.9%) transported by HEMS had minor injuries and 25.8% (99% CI: -1.0%-52.6%) were discharged within 24 hours .
Patients transported by HEMS in NSW may be over-triaged, however, our data did not allow assessment of transport protocol adherence. In NSW, HEMS are currently activated either by emergency call information (via a rapid launch coordinator) or via on on-scene paramedic according to service protocols, which rely on criteria such as patient physiology and mechanism of injury. In terms of discriminative accuracy, previous research has shown currently used criteria (including injury mechanism, physiology and anatomy of injury) to rely on a limited evidence base . Our results confirm the advanced diagnostic capability and oversight which is possible in inter-hospital transfers lead to patients with a higher acuity being transferred by HEMS. Although such capabilities are not available in the pre-hospital environment and a degree of over-triage is always likely to exist, there remains scope for further research in this area. However, more comprehensive data are needed (linking ambulance to trauma registry and long-term outcomes) to understand which patients benefit from a HEMS intervention and why. From the health system perspective, such data would allow for possible improvements in the cost-effectiveness of a HEMS intervention . Additionally, from the perspective of the receiving hospital, improved HEMS triage would possibly allow more efficient resource allocation to patients who require more of the services offered at a major trauma centre.
During the study period, a HEMS pre-hospital and inter-hospital patient cost, on average, ~$25,000 and ~$42,000 respectively to treat, although considerable variation existed between patients, which has also been demonstrated previously . Our results show HEMS patients are potentially underfunded in the order of ~$2,500 - ~$2,900 per patient transported pre-hospital and inter-hospital respectively. Overall, the potential funding discrepancy was over $1.7 m for the entire year. These results support the need for further research to refine funding models to account for the complexity of trauma patients.
In terms of the cost of over-triage to the major trauma centre, we found treating patients transported by HEMS with minor to moderate injuries (according to the NSW definition; ISS<12) led to a shortfall between the cost of treatment and potential reimbursement of ~$542,000, split evenly between pre-hospital and inter-hospital transports. Previous research has shown more inaccuracy in the episode funding model in less severely injured patients  and our results support these findings. Although a proportion of pre-hospital over-triaged patients would have received care at the same centre if transported by other transport modes, HEMS pre-hospital responses in NSW often bypass the closest designated trauma hospital . Therefore, the cost implications of HEMS over-triage to a major trauma centre is a significant consideration.
Another implication of our results is the difference in patient acuity, cost and reimbursement between HEMS patients transported directly from the scene and inter-hospital. Our findings showed patients transported inter-hospital were older, had longer lengths of stayed and consumed more resources, particularly in the ICU. In terms of potential funding discrepancies, our results showed inter-hospital patients with minor injuries had the largest discrepancies compared to patients transported pre-hospital. Currently, hospitals in NSW receive variable amounts of pre-hospital and inter-hospital HEMS transports. Given the differences between HEMS patients transported directly from the scene and inter-hospital, future funding models also need to account for these differences.
This study includes the first comprehensive cohort of patients transported by HEMS to major trauma centres in NSW. However, due to excluded hospitals as well as potentially inconsistent data collection in some included hospitals, our study carries several limitations. We were unable to gather information for hospitals other than major trauma centres (such as regional trauma centres) that receive trauma patients via HEMS. However this is only likely to represent a small proportion of total transports. Some trauma centres did not collect comprehensive data for minor trauma patients, and therefore our data may be an under-representation of this patient group. Finally, it should be noted that our estimate of reimbursement used is based on the peer group averages and do not account for the potential additional weightings for aspects such as public or private status, aboriginality and longer lengths of stay. However, our results are a robust estimate of the true costs of treating HEMS patients relative to the average costs for the same patients among similar peer group hospitals.