Department of Biomedical Engineering, Wayne State University , Detroit, MI , USA.
Front Neurol. 2013 Aug 2;4:88. doi: 10.3389/fneur.2013.00088. eCollection 2013.
Blast-induced traumatic brain injury has emerged as a "signature injury" in combat casualty care. Present combat helmets are designed primarily to protect against ballistic and blunt impacts, but the current issue with helmets is protection concerning blasts. In order to delineate the blast wave attenuating capability of the Advanced Combat Helmet (ACH), a finite element (FE) study was undertaken to evaluate the head response against blast loadings with and without helmet using a partially validated FE model of the human head and ACH. Four levels of overpressures (0.27-0.66 MPa) from the Bowen's lung iso-damage threshold curves were used to simulate blast insults. Effectiveness of the helmet with respect to head orientation was also investigated. The resulting biomechanical responses of the brain to blast threats were compared for human head with and without the helmet. For all Bowen's cases, the peak intracranial pressures (ICP) in the head ranged from 0.68 to 1.8 MPa in the coup cortical region. ACH was found to mitigate ICP in the head by 10-35%. Helmeted head resulted in 30% lower average peak brain strains and product of strain and strain rate. Among three blast loading directions with ACH, highest reduction in peak ICP (44%) was due to backward blasts whereas the lowest reduction in peak ICP and brain strains was due to forward blast (27%). The biomechanical responses of a human head to primary blast insult exhibited directional sensitivity owing to the different geometry contours and coverage of the helmet construction and asymmetric anatomy of the head. Thus, direction-specific tolerances are needed in helmet design in order to offer omni-directional protection for the human head. The blasts of varying peak overpressures and durations that are believed to produce the same level of lung injury produce different levels of mechanical responses in the brain, and hence "iso-damage" curves for brain injury are likely different than the Bowen curves for lung injury.
爆炸伤性脑损伤已成为战场上伤员救治的“标志性损伤”。目前的作战头盔主要设计用于防护弹道和钝性冲击，但目前头盔的问题是对爆炸的防护。为了描绘先进战斗头盔（ACH）的冲击波衰减能力，采用部分验证的人体头部和 ACH 的有限元模型，对头盔在有和没有头盔的情况下对抗爆炸负荷的头部响应进行了有限元研究。使用来自 Bowen 肺等效应损伤阈值曲线的四个过压水平（0.27-0.66 MPa）来模拟爆炸冲击。还研究了头盔相对于头部方向的有效性。比较了有和没有头盔的情况下，大脑对爆炸威胁的生物力学响应。对于所有 Bowen 情况，头部的颅内峰值压力（ICP）在冲击皮质区域范围从 0.68 到 1.8 MPa。发现 ACH 可使头部的 ICP 降低 10-35%。戴头盔的头部导致平均峰值脑应变和应变率乘积降低 30%。在有 ACH 的三种爆炸加载方向中，由于反向爆炸，ICP 的峰值降低了 44%，而由于正向爆炸，ICP 和脑应变的峰值降低了 27%。由于头盔结构的几何轮廓和覆盖范围以及头部的不对称解剖结构的不同，人体头部对原发性爆炸冲击的生物力学响应表现出方向敏感性。因此，头盔设计需要特定方向的耐受性，以便为头部提供全方位保护。据信，峰值超压和持续时间不同的爆炸会在大脑中产生不同水平的机械响应，因此，脑损伤的“等效应”曲线可能与肺损伤的 Bowen 曲线不同。
