A Magnetic Sensor Approach to Position Damage Control Stent Grafts in the Austere Environment

INTRODUCTION: Noncompressible torso hemorrhage has high mortality, with difficulty mobilizing resources before exsanguination. We reported on a retrievable stent graft for damage control and human vascular morphometry, yet the gold standard of fluoroscopy for device placement is infeasible in austere environments. We hypothesized that a magnetic sensor could be used to position stent grafts relative to an external magnet when fluoroscopy is not immediately available. METHODS: Two sensors (alone and with retrievable stent) were tested in a porcine model under anesthesia. A target electromagnet was placed on the xiphoid (position 0 cm). Sensors were placed in the aorta and measurements obtained at 0, +4, and +12 cm from the magnet. Measurements were compared with fluoroscopy using a radiopaque ruler. To simulate hostile environments, sensors were tested under conditions of tachycardia (epinephrine; HR: 174, MAP: 139), hypotension (hemorrhagic shock; MAP: 16), unstable transportation (vibration) and metallic shrapnel. Data were compared with t-test of differences between fluoroscopy and sensor readings. RESULTS: Mean differences between fluoroscopy and sensor readings for sensor alone were baseline: 0.07 cm (p = 0.59); metal: −0.19 (p = 0.14); vibration: −0.35 (p = 0.01); epinephrine: −0.26 (p = 0.04); hemorrhage: −0.39 (p = 0.002). Mean differences for sensor with stent were baseline: −0.21 (p = 0.10); epinephrine: −0.27 (p = 0.03); hemorrhage: −0.36 (p = 0.005). Fig. 1 demonstrates accuracy at 0 and +4 cm.CONCLUSION: Magnetic sensor readings were within 0.5 cm of the target with increased accuracy as sensors approached the target. The on/off electromagnet feature allows the system to account for environmental noise. This approach is promising for rapid and accurate placement of damage control retrievable stents when fluoroscopy is impractical.