A study has been carried out to assess the effect on injury level of the parameters which characterise a non-penetrating thoracic impact. This study has used the dynamic finite element code DYNA2D⁽¹⁾ and the dynamic simulation code GENDYN⁽²⁾ . Injury level has been calculated using a range of criteria. These criteria have included the maximum acceleration of the chest wall and Viano’s Viscous Criterion⁽³⁾ based on chest wall motion as well as criteria based more closely on the factors which actually produce the injury (such as the maximum rates of change of pressure (dP/dt_max) generated in the lung parenchyma during the impact).

The study has shown that acceleration of the outside of the chest wall is a very poor indicator of the expected injury level, bearing little or no relationship to the actual pressure conditions in the lung. Viscous Criterion based on internal motion of the chest wall has been shown to be a good criterion and the maximum chest wall internal velocity or acceleration also show good agreement with expected injury level. The best criteria are those which take account of dP/dt_max, at all points in the lung. Injury indices based on these criteria are very difficult to determine experimentally but mathematical modelling can calculate their values without undue difficulty.