Pulmonary hypoxia and venous admixture correlate linearly to the kinetic energy from porcine high velocity projectile behind armor blunt trauma

Abstract

Purpose. Behind armor blunt trauma (BABT) is a non-penetrating injury caused by the rapid deformation of body armor, by a projectile, which may in extreme circumstances cause death. The understanding of the mechanisms is still low, in relation to what is needed for safety threshold levels. High velocity projectile BABT causes immediate and severe hypoxia by increased venous admixture (Q's/Q't), but it is not known whether the level of hypoxia correlates to the kinetic energy (E k ) of the projectile. Materials and Methods. We constructed a 65 mm BABT-simulator to measure the E k absorbed by the thorax. The simulator was validated to 7.62 mm high velocity BABT (swine with removed organs) for 7.62 mm (n = 7) and 65 mm (n = 12). Physiological measurements during 60 minutes were performed in 40 anesthetized swine in groups control (n = 9), 7.62 mm (n = 7), 65 mm weight variation (n = 24), 65 mm speed variation (n = 12, included in the weight variation group). New calculations were done for a previously studied group of 7.62 mm with backing (n = 9). Results. 65 mm BABT simulation and 7.62 mm BABT had similar back-face signatures (24 mm), and maximum thoracic impression speed (24-34 m/s). Back-face signatures correlated linearly to E k (R 2 =0.20). Rib fractures had a 50% likelihood at back-face signature 23.0 mm (95% CI 18.5 to 29.0 mm, area under ROC curve 0.93). E k correlated linearly to pO 2 (R 2 =0.34, p = 0.0026) and venous admixture (R 2 =0.37, p = 0.0046). The extrapolated E k at 5 minutes for pO 2 =0 kPa was 587 J and for venous admixture = 100% 574 J. Conclusions. Hypoxia and venous admixture correlated linearly to E k , allowing for a calculated predicted lethal E k to ≥574 J, which should be verified in survival studies. Lethality predictions from lung physiology is an alternative to clay impressions and may facilitate the development of ballistic safety equipment and new BABT safety criteria.

Determination of the Worst Case for the Ballistic Test of the Soft Armour System Using the 9mm FMJ Bullets Differing in the Structure

“…During the design development of the above-mentioned products, parameters were introduced into the safety assessment, which indirectly verified the amount of energy transmitted to the user's body in the event of a nonpenetrating shot on the body armour. This effect, called Behind Armour Blunt Trauma (BABT), represents the risk of injury to the user's body by transferring the impact energy of the projectile minus the amount of energy absorbed by the ballistic shield and the bullet deformation energy [1][2]. The value of BABT allows to estimate the risk of bone damage and lethal damage to viscera.…”