Cost-effectiveness of helicopter versus ground emergency medical services for trauma scene transport in the United States

Abstract

Study objective: We determine the minimum mortality reduction that helicopter emergency medical services (EMS) should provide relative to ground EMS for the scene transport of trauma victims to offset higher costs, inherent transport risks, and inevitable overtriage of patients with minor injury.

Methods: We developed a decision-analytic model to compare the costs and outcomes of helicopter versus ground EMS transport to a trauma center from a societal perspective during a patient's lifetime. We determined the mortality reduction needed to make helicopter transport cost less than $100,000 and $50,000 per quality-adjusted life-year gained compared with ground EMS. Model inputs were derived from the National Study on the Costs and Outcomes of Trauma, National Trauma Data Bank, Medicare reimbursements, and literature. We assessed robustness with probabilistic sensitivity analyses.

Results: Helicopter EMS must provide a minimum of a 15% relative risk reduction in mortality (1.3 lives saved/100 patients with the mean characteristics of the National Study on the Costs and Outcomes of Trauma cohort) to cost less than $100,000 per quality-adjusted life-year gained and a reduction of at least 30% (3.3 lives saved/100 patients) to cost less than $50,000 per quality-adjusted life-year. Helicopter EMS becomes more cost-effective with significant reductions in patients with minor injury who are triaged to air transport or if long-term disability outcomes are improved.

Conclusion: Helicopter EMS needs to provide at least a 15% mortality reduction or a measurable improvement in long-term disability to compare favorably with other interventions considered cost-effective. Given current evidence, it is not clear that helicopter EMS achieves this mortality or disability reduction. Reducing overtriage of patients with minor injury to helicopter EMS would improve its cost-effectiveness.

Figure 1. Model structure

The model calculates the difference in the costs and outcomes related to the decision of choosing helicopter EMS as opposed to ground EMS for the scene transport of an injured patient to a U.S. trauma center. Event probabilities and their associated costs conditional on strategy chosen (helicopter vs. ground) and injury severity are presented in Table 1. A Markov model was used to calculate remaining patient life expectancy and lifetime health care expenditures for the cohort of patients who survive to be discharged from the hospital.

Figure 2. Relationship between relative reduction in mortality and the cost-effectiveness of helicopter EMS

ICER: incremental cost-effectiveness ratio. AIS: Abbreviated Injury Scale. 2A) Base case analysis. The plotted line represents the cost-effectiveness of helicopter EMS relative to ground EMS as a function of the assumed mortality reduction provided by helicopter EMS given the base case assumptions described in Table 1. 2B) Effect of overtriage rate on cost-effectiveness of helicopter EMS. Based on analysis of national data, 47% of patients transported by helicopter EMS have only minor injuries. The two dotted lines demonstrate how the cost-effectiveness of helicopter EMS changes based on the highest and lowest regional overtriage rates observed in national data. 2C) Effect of difference in disability outcomes on cost-effectiveness of helicopter EMS. In our base case, we assume no difference in disability outcomes. The two dotted lines demonstrate how the cost-effectiveness of helicopter EMS changes based on whether helicopter EMS is associated with worse or better disability outcomes as measured by the SF-6D quality of life scale over the course of a lifetime.

Figure 3. Effect of the variation in the added cost of helicopter EMS on the threshold mortality reduction needed to be cost-effective

ICER: incremental cost-effectiveness ratio. RR: relative risk ratio. Based on the Medicare Fee Schedule, we assume that the helicopter EMS costs about $5,700 more than ground EMS transport for patients located 55-miles from a trauma center (our base case assumption). The plotted lines demonstrate how the cost-effectiveness of helicopter EMS would change based on the assumed relative mortality reduction and the regional variation in the added cost of helicopter EMS over ground EMS.

Figure 4. Probabilistic sensitivity analysis of the incremental cost-effectiveness ratio of helicopter EMS versus ground EMS for trauma scene transport according to the size of the relative mortality reduction from helicopter EMS

A threshold mortality reduction of ≥28% (RR 0.72) is needed for helicopter EMS to be cost-effective in ≥ 95% of simulations if society is willing to pay $100,000 per QALY gained. This is a higher threshold mortality reduction than the threshold of 17% (RR 0.83) that was determined using base-case assumptions. The threshold of 17% (RR 0.83) was cost-effective in 52% of simulations if society is willing to pay $100,000 per QALY gained.