Multi-Injury Casualty Stream Simulation in a Shipboard Combat Environment

MILITARY MEDICINE, 181, 1:70, 2016 Multi-Injury Casualty Stream Simulation in a Shipboard Combat Environment Edwin D’Souza, MS*; Vern Wing, MS*; James Zouris, MS*; Ross Vickers, PhD*; Mary Lawnick, BSN†; Michael Galarneau, MS* ABSTRACT Accurate forecasts of casualty streams are essential for estimating personnel and materiel requirements for future naval combat engagements. The scarcity of recent naval combat data makes accurate forecasting difficult. Furthermore, current forecasts are based on single injuries only, even though empirical evidence indicates most battle casualties suffer multiple injuries. These anticipated single-injury casualty streams underestimate the needed medical resources. This article describes a method of simulating realistic multi-injury casualty streams in a maritime environment by combining available shipboard data with ground combat blast data. The simulations, based on the Military Combat Injury Scale, are expected to provide a better tool for medical logistics planning. INTRODUCTION Medical logistics planners need accurate estimates of personnel and materiel requirements for future naval combat engagements. These estimates must be based on realistic casualty stream projections. These projections describe the casualty case mix over time. Accurate casualty stream forecasting is difficult because recent naval combat data are scarce (Naval Health Research Center [NHRC], 2010, Report No. 10-56). Most of the available data are from World War II (WWII). Furthermore, current Department of Defense casualty stream simulations generate casualties with single injuries only (NHRC, 2010, Report No. 10-56; 2013, Report No. 13-06; 2013, Report No. 13-40; 2013, Report No. 13-60).1,2 This approach will only be accurate if injured personnel present with one major complaint and all other injuries require minimal care. Unfortunately, empirical data show most casualties suffer multiple injuries or polytrauma. Casualties with multiple injuries impose a different medical load than those with single injuries, so the inability to generate multi-injury casualty streams underestimates the needed medical resources. The estimation problem is compounded by the inability to simulate the severity of the casualties’ injuries. Injury severity can vary from minor to life threatening, and the medical treatment will vary as a function of that severity rating. Recently, the Military Combat Injury Scale3 (MCIS) coding taxonomy was developed by a panel of civilian and tri-service military experts. Because of the inability to code many militarygrade injuries using civilian low-velocity, blunt-trauma-based injury taxonomies, MCIS was developed to provide a more accurate and reliable method of coding combat-specific injuries. In addition to providing a description of the specific *Medical Modeling, Simulation, and Mission Support Department, Naval Health Research Center, 140 Sylvester Road, San Diego, CA 92106. †SimQuest Solutions, Inc., 954 Melvin Road, Annapolis, MD 21403. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the U.S. Government. doi: 10.7205/MILMED-D-15-00002 70 injury, the MCIS code provides injury severity rated on a scale of 1 to 5 and specifies the affected body region. This article describes an MCIS-based method of simulating realistic multi-injury casualty streams in a maritime environment by combining available shipboard data with blast data accumulated from ground engagements in Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF). METHODS Data Sources Data from WWII captured 12,067 injuries for 513 incidents in which U.S. Navy warships were sunk or damaged.4 Although ship and weapon design have changed markedly since that era, the effects of explosive events in closed spaces on humans has changed very little (NHRC, 2010, Report No. 10-56).5,6 WWII data are principally limited to categories of injury (e.g., burns, fractures, amputations) vice specific diagnostic codes. This work seeks to bridge the category-code divide by retaining the afloat injury distributions across categories and combining available shipboard data with more recent ground combat blast data. The combination yields discrete probability distributions that generate more descriptive and predictive casualty streams. The polytrauma profiles needed to estimate the frequency of specific injuries within the general categories are based on medical encounter records from the NHRC Expeditionary Medical Encounter Database (EMED).7 The EMED is a triservice database that includes data for all injuries sustained during OEF and OIF combat operations for the time 2003 through today. Because the database is comprehensive and includes mechanism of injury and injury severity among its variables, we used it to select the MCIS-coded, blast injury cases used in this article. AIREX and UNDEX Trauma Category Distributions Using WWII shipboard data, NHRC has compiled two MCIS-based discrete probability distributions for injury by MILITARY MEDICINE, Vol. 181, January 2016 Casualty Stream Simulation in a Shipboard Combat Environment TABLE I. AIREX and UNDEX Distribution of Trauma Categories in World War II Shipboard Data Trauma Category AIREX(%) UNDEX(%) a 3.00 1.34 25.30 2.85 7.06 6.70 4.96 2.00 44.88 1.91 100.00 3.00 3.50 15.09 9.29 16.28 11.52 12.08 2.00 20.49 6.75 100.00 Amputations Asphyxiations Burns Concussions/Internal Organs Contusions/Abrasions Fractures Miscellaneous Nonfatal Immersions Penetrating Wounds Sprains/Strains/Dislocations Total AIREX, attacks above the waterline; UNDEX, attacks at or below the waterline. aAmputations and nonfatal immersions are subject matter expertadjusted values. trauma category. These distributions are called AIREX (for ship/weapon interactions where the weapon interaction is above the waterline) and UNDEX (for underwater explosions where the weapon interaction is at or below the waterline). AIREX includes attacks from missiles, bombs, and gunfire, whereas UNDEX includes attacks from torpedoes, mines, and vessel-borne improvised explosive devices (NHRC, 2013, Report No. 13-60). Table I shows these distributions. The ship survivability community commonly refers to attacks that occur at the waterline as SURFEX. Because blast events at the waterline (SURFEX) could not be pulled out of the data as their own entity, SURFEX attacks are treated as UNDEX attacks for the purpose of this study. The AIREX and UNDEX trauma category distributions specify the probability of occurrence of the following 10 trauma categories among shipboard casualties: amputations, asphyxiations, burns, concussions/internal organs, contusions/ abrasions, fractures, nonfatal immersions (near drowning), penetrating wounds, sprains/strains/dislocations, and miscellaneous. The amputations and nonfatal immersions category proportions were adjusted upward by subject matter expe (...truncated)