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• Comment on "Development of unmanned aerial vehicle (UAV) networks delivering early defibrillation for out-of-hospital cardiac arrests (OHCA) in areas lacking timely access to emergency medical services (EMS) in Germany: a comparative economic study"
  Elizabeth M Ashley
  Published on: 10 August 2021

• Published on: 10 August 2021

  Comment on "Development of unmanned aerial vehicle (UAV) networks delivering early defibrillation for out-of-hospital cardiac arrests (OHCA) in areas lacking timely access to emergency medical services (EMS) in Germany: a comparative economic study"

  • Elizabeth M Ashley, Economist N/A

  Although there is extensive scholarly interest in public access defibrillation, including a noteworthy strand of literature about drone delivery of automated external defibrillators (AEDs), cost-effectiveness assessments are still quite rare, and Bauer et al. [1] do well to combine cost considerations with national scope and attentiveness to geographic details. However, there is an inconsistency between the numerators and denominators in their incremental cost-effectiveness ratio (ICER) calculations, as will be discussed in this Rapid Response.

  Categories of cost included in Bauer et al.’s study include purchase and maintenance of drones (also known as unmanned aerial vehicles, UAV) and AEDs. These cost categories could be sufficient if the research or policy question being posed were focused on the minutes immediately following out-of-hospital cardiac arrest (OHCA)—for example, cost-effectiveness could be calculated per OHCA survival measured at the time of emergency department arrival. Instead, Bauer et al. follow more common practice and include in their denominators life-years saved—a longer-run value. As the authors notes: “The reference period for the [ICER] calculation was the first 12 years (mean life expectancy of OHCA survivor).” It is therefore necessary for twelve years’ worth of costs to be captured in ICER numerators.

  As noted in eTable 15 of Andersen et al. [2] and Table 2 of Kumar et al. [3], cost-effectiveness studies of public access...

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  Although there is extensive scholarly interest in public access defibrillation, including a noteworthy strand of literature about drone delivery of automated external defibrillators (AEDs), cost-effectiveness assessments are still quite rare, and Bauer et al. [1] do well to combine cost considerations with national scope and attentiveness to geographic details. However, there is an inconsistency between the numerators and denominators in their incremental cost-effectiveness ratio (ICER) calculations, as will be discussed in this Rapid Response.

  Categories of cost included in Bauer et al.’s study include purchase and maintenance of drones (also known as unmanned aerial vehicles, UAV) and AEDs. These cost categories could be sufficient if the research or policy question being posed were focused on the minutes immediately following out-of-hospital cardiac arrest (OHCA)—for example, cost-effectiveness could be calculated per OHCA survival measured at the time of emergency department arrival. Instead, Bauer et al. follow more common practice and include in their denominators life-years saved—a longer-run value. As the authors notes: “The reference period for the [ICER] calculation was the first 12 years (mean life expectancy of OHCA survivor).” It is therefore necessary for twelve years’ worth of costs to be captured in ICER numerators.

  As noted in eTable 15 of Andersen et al. [2] and Table 2 of Kumar et al. [3], cost-effectiveness studies of public access defibrillation typically include health care costs. Graf et al. [4], estimate that, in Germany as of 2004, hospital costs and post-discharge costs totaled approximately €29,000 per individual experiencing cardiac arrest and surviving at least to the point of being admitted to the intensive care unit (ICU). [a] Germany’s Statistisches Bundesamt (Result 23611-0002) reports that health care expenditures rose approximately 75 percent between 2004 and 2019; applying this growth rate to the €29,000 estimated by Graf et al. yields an updated cost estimate of approximately €51,000 per survival to ICU. If, as estimated by Bauer et al., a UAV network increases survival rates from 13.2 percent to 33.1 percent for 1,427 yearly cases of OHCA with shockable rhythms, then the associated annual cost would be €14.5 million.

  This simple multiplication slightly overstates incremental treatment costs because timely AED use can improve the neurologic function of OHCA survivors, which in turn leads to cost reductions. Andersen et al. [2] report the distribution of OHCA outcomes (eTable 10, citing Andersen et al. [5]) across Cerebral Performance Categories (CPC), along with U.S. hospital costs (eFigure 9, citing Geri et al. [6]) and U.S. post-discharge costs (eTable 8, citing Chan et al. [7]) as functions of CPC. Using these inputs to adjust the German cost estimates derived and updated from Graf et al. yields an estimated net annual treatment cost of €13.2 million. [b]

  Bauer et al.’s ICER estimates (omitting treatment costs) are €23,568 for a UAV network that achieves time to defibrillation of under 10 minutes for 100 percent of OHCA currently experiencing delays that are over that threshold; €14,548 for 90 percent coverage; and €12,158 for 80 percent coverage. Adjusting these undiscounted results to reflect a 3 percent discount rate (following [2] and [4]) increases the ICER estimates to €25,500, €15,700 and €13,200. Further adjustments, to incorporate 100, 90, or 80 percent of the €13.2 million treatment cost estimated above, yield ICER estimates of €33,100, €23,200 and €20,700. [c]

  Along with Bogle et al. [8], the analysis performed by Bauer et al. is pioneering in the application of the cost-effectiveness concept to UAV delivery of AEDs, but both studies inappropriately diverge from the practice of matching the time periods assessed in cost-effectiveness ratios’ numerators and denominators. As is done elsewhere in the public access defibrillation literature, health care costs should be estimated and included, toward the goal of achieving plausible cost-effectiveness estimates.

  [a] Following Andersen et al. [2], I assume that emergency department costs are unaffected by OHCA survival.

  [b] This result depends not only on the absolute change in OHCA survival brought about by timely AED use but also on the starting survival rate. Andersen et al. [5] estimate that AED use increases the probability of favorable outcomes, after OHCA with shockable rhythm, from 39 percent to 58 percent—a percentage-point change remarkably similar to the difference between the 13.2 percent and 33.1 percent estimates used as inputs by Bauer et al. However, with nearly three times more baseline survivors potentially experiencing improved neurologic function due to timely defibrillation, the net annual treatment cost would instead be €12.1 million.

  [c] Bauer et al. calculate only the life-years that are estimated to be saved within the twelve-year reference period of the analysis. If instead twelve cohorts’ worth of twelve-year life extensions are included, the ICER results calculated with a 3 percent discount rate would be €15,800, €9,700 and €8,200 (omitting treatment costs) or €20,400, €14,400 and €12,800 (including treatment costs).

  REFERENCES

  1. Bauer J, Moormann D, Strametz R, et al. Development of unmanned aerial vehicle (UAV) networks delivering early defibrillation for out-of-hospital cardiac arrests (OHCA) in areas lacking timely access to emergency medical services (EMS) in Germany: a comparative economic study. BMJ Open 2021;11:e043791. doi:10.1136/bmjopen-2020-043791

  2. Andersen LW, Holmberg MJ, Granfeldt A, et al. Cost-effectiveness of public automated external defibrillators. Resuscitation 2019;138:250-2589. https://doi.org/10.1016/j.resuscitation.2019.03.029

  3. Kumar S, Chow C, Jan S, et al. Rapid Literature Review on Public Access to Defibrillation, September 2017. https://www.health.nsw.gov.au/cardiacarrest/Publications/defibrillators-...

  4. Graf J, Mühlhoff C, Doig GS, et al. Health care costs, long-term survival, and quality of life following intensive care unit admission after cardiac arrest. Critical Care 2008;12:R92. http://ccforum.com/content/12/4/R92

  5. Andersen LW, Holmberg MJ, Granfeldt A, et al. Neighborhood characteristics, bystander automated external defibrillator use, and patient outcomes in public out-of-hospital cardiac arrest. Resuscitation 2018;126:72-79.

  6. Geri G, Fahrenbruch C, Meischke H, et al. Effects of bystander CPR following out-of-hospital cardiac arrest on hospital costs and long-term survival. Resuscitation 2017;115:129-134.

  7. Chan PS, McNally B, Nallamothu BK, et al. Long-Term Outcomes Among Elderly Survivors of Out-of-Hospital Cardiac Arrest. J Am Heart Assoc. 2016;5(3):e002924

  8. Bogle BM, Rosamond WD, Snyder KT, et al. The case for drone-assisted emergency response to cardiac arrest. N C Med J 2019;80:204-12.

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  Conflict of Interest:
  None declared.

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