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A Spatial Analysis of Incident Location and Prehospital Mortality for Two United Kingdom Helicopter Emergency Medical Services (HEMS)

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Abstract

Most trauma and out of hospital cardiac arrest (OHCA) deaths occur prior to arrival at hospital, with increased risk for rural compared to urban patients. Essex and Hertfordshire Air Ambulance Trust (EHAAT) and Kent Surrey Sussex Air Ambulance Trust (KSS) provide a physician-paramedic Helicopter Emergency Medical Service (HEMS) in two regions of the United Kingdom. We investigated whether an association exists between prehospital mortality and distance from care in HEMS patients. We performed a retrospective study using spatial statistics to investigate the geographic distribution of scene outcome (alive versus deceased). We also performed multiple logistic regression of outcome against quartiles of distance from base to scene and a relative risk (RR) estimation over the operational areas. Organisations were analysed separately to assess consistency of spatial relationships. 2680 EHAAT and 4213 KSS patients met the inclusion criteria. Ripley’s K and Cross K functions indicated that outcomes (death and leaving the scene alive) cluster together. For KSS distance was not associated with outcome, for EHAAT distance was a significant predictor of mortality at furthest distance (41 to 95 km; OR 5.82, 95%CI 1.63 to 37.18, p = 0.019). Only one area of KSS and no areas of EHAAT had an increased RR of mortality. In contrast to previous research of pre-hospital patients, we found little evidence of geographic difference in scene outcome for trauma patients attended by the two HEMS services. Increased mortality risk for OHCA at the furthest distance from helicopter base was found in one organisation; a single area of increased RR of mortality was found for the other organisation.

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Acknowledgements

The authors would like to thank the paramedics and doctors of EHAAT and KSS for clinical care of patients and data entry following each mission. We would also like to thank both organisations for allowing us to access the data for this study.

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Authors and Affiliations

  1. Aeromedical Operations, New South Wales Ambulance, Bankstown Airport, Sydney, Australia

    Matthew Miller

  2. Department of Anaesthesia and Pain Medicine, St George Hospital, Grey St, Kogarah, Sydney, New South Wales, Australia

    Matthew Miller & Ilana Delroy-Buelles

  3. St George and Sutherland Clinical Schools, University of New South Wales, Sydney, Australia

    Matthew Miller

  4. Essex and Hertfordshire Air Ambulance Trust, Earls Colne, Essex, UK

    Ilana Delroy-Buelles

  5. Brighton and Sussex University Hospitals NHS Trust, Brighton, UK

    Duncan Bootland

  6. Kent Surrey Sussex Air Ambulance Trust, Marden, Kent, UK

    Duncan Bootland & Richard Lyon

  7. University of Surrey, Guildford, UK

    Richard Lyon

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  1. Matthew Miller
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  2. Ilana Delroy-Buelles
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  4. Richard Lyon
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Contributions

MM conceived of the study, MM, ID-B, DB and RL all contributed to the study design, ID-B and DB provided the data, MM performed the analysis, MM, ID-B, DB and RL all interpreted the data. MM drafted the manuscript, ID-B, DB and RL all contributed to manuscript review and revision.

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Correspondence to Matthew Miller.

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MM reports no conflict of interest.

ID-B reports no conflict of interest.

DB reports no conflict of interest.

RL reports no conflict of interest

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Miller, M., Delroy-Buelles, I., Bootland, D. et al. A Spatial Analysis of Incident Location and Prehospital Mortality for Two United Kingdom Helicopter Emergency Medical Services (HEMS). Appl. Spatial Analysis 13, 575–590 (2020). https://doi.org/10.1007/s12061-019-09318-2

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