Abstract
This thesis is addressing Behind Armor Blunt Trauma (BABT), defined as
the nonpenetrating injury resulting from a ballistic impact on personal
body armor. The protective vest may impede the projectile, but some of
the kinetic energy is transferred to the body, causing effects such as
pulmonary contusion, apnea, hypotension and occasionally death.
Our aims of these studies have been to investigate physiological
responses after highvelocity BABT, including EEG (study I). Furthermore,
the safety criterion of 44 mm for protective vests (study II), effects of
vagotomy (study III), and fluid resuscitation (study IV) has been
evaluated.
Anaesthetized pigs, wearing body armor on the right side of thorax, were
shot with a standard 7.62 mm assault rifle (velocity approx. 800 m/s). We
used body armors corresponding to 28 mm impression in clay placed behind
the vest (study I and III), 34 mm and 40 mm (study II), and 42 mm (study
IV). Several physiological parameters were thereafter monitored during
two hours after the shot. Experimental protocol was similar in all
studies, except from study III (in which one group received bilateral
cervical vagotomy) and study IV, in which 2 groups received Ringer´s
acetate (RA) or hypertonic saline with dextrane (HSD).
In all studies we observed an immediate drop of blood pressure,
desaturation, increased pressure in the lung circulation, suppressed
EEG-pattern and pulmonary contusion. In study II and IV, severe
hyperkalemia was seen early after the trauma and several animals had
serious arrhythmias. Our observed EEG-changes indicate that high-velocity
BABT induces brain dysfunction, for at least a couple of minutes. Based
on our results, the safety criteria of 44 mm should be considered
insufficient when a vest is exposed to highvelocity bullets. Our results
show that apnea after BABT is a vagally mediated reflex, that can be
inhibited by vagotomy. Fluid resuscitation has limited effects on
physiological parameters in our model, although HSD induces less edema
formation and a tendency to improved saturation compared to RA.
