Hemorrhage is the leading cause of preventable battlefield deaths 1 and damage control resuscitation (DCR) following trauma saves lives in both military and civilian settings.2-3 The Joint Trauma System Clinical Practice Guideline (JTS CPG) recommends the use of intraosseous (IO) access for transfusing resuscitative fluids or blood when IV access cannot be established.4 The Joint Theatre Trauma Registry (JTTR) found that IO access was performed more than 1000 times in the OEF Afghanistan conflict alone.5 IO pressure infusion strategies vary, including push-pull, pressure bag, and hand bulb techniques. 6, 7 Auten and colleagues 8,9, 10-12 previously described the flow rates and peak pressures of IO techniques currently employed. No studies have specifically explored the user characteristics of these techniques. Effective IO pressure infusion can be optimized if the user is confident and comfortable with device use and if the infusion technique does not result in excessive hand fatigue. This study was designed to fill this important gap in the literature by evaluating which devices meet these criteria and ultimately contribute towards preserving the life of the traumatically hemorrhaging warfighter. Using a mannequin simulation model, users infused simulated blood through an IO needle into a simulated humerus. This study employed a randomized within-subjects design, such that each participant used and then evaluated the pressure bag, push-pull, and hand bulb devices. Participants completed both written informed consent and a pre-experiment survey. Pretraining included a lecture on basic mechanics of IO transfusion and instruction on the three specific infusion techniques. Formal data collection began when each participant indicated that they are comfortable with the study procedures and all questions were answered. Each user performed IO techniques in a randomly assigned order, then completed an exit survey. The primary endpoint was user comfort of the three techniques measured by the following exit survey questions: preferred method, confidence, perceived reliability, one-hand usability, and hand fatigue. Secondary end points were set-up time and infusion rates. Open-ended questions allowed users to provide detailed qualitative feedback regarding the usability of three techniques. This study includes two arms. The participants in Arm 1 are Navy Corpsmen with Tactical Combat Casualty Care (TCCC) training. The participants in Arm 2 are Naval Special Warfare Special Operations Tactical Medics (SOTMs). Data from the two arms will be analyzed in parallel. This study is of great importance towards preserving the lives of traumatically wounded warfighters who require rapid infusion of blood or resuscitative fluids. Data collection is ongoing and near completion at the time of this abstract. We anticipate completion of the study and data analysis by the end of October 2023.