Scaling in Blast Neurotrauma

The high incidence of blast exposure on today’s battlefield has been strongly associated with traumatic brain injuries. Anecdotal evidence of prolonged apnea following blast exposure has been observed in military personnel and is commonly reproduced in animal neurotrauma models. Animal models have shown that apnea tolerance is both dose and species-dependent; important factors include primary blast characteristics (peak overpressure, P, and duration, Δt) and animal size. Experimental data on apnea from head exposure to primary blast were obtained from 121 tests using four different-sized animal models with thoracic blast protection: mouse, rabbit, ferret and pig with peak incident pressure and overpressure duration ranging from 99.7 to 1084.6kPa and 0.6 to 8.0ms, respectively. Apnea risk was assessed using logistic regression with a log-linear dose-response. Scaling procedures were explored based upon the body mass or brain mass of the animal. Scaling effects were largest in the small animal models. When scaling was applied to existing rodent neurotrauma models, scaled duration ranged from 17.65 to 540 ms, with most larger in duration than the typical blast exposure range seen in combat (~1-40 ms duration). It is imperative that appropriate scaling procedures between species are derived and implemented to properly correlate animal model pathophysiological outcomes with human response.