1973-02-01

Thoracic Impact: New Experimental Approaches Leading to Model Synthesis 730981

The following work was done in support of a continuing program to better characterize the behavior of the human chest during blunt sternal impact. Previous work on this problem has focused on determining the force-time, deflection-time, and force-deflection response of embalmed and fresh cadavers to impact by a 15 cm (6 in) diameter striker of variable mass traveling at velocities of 22.5-51 km/h (14-32 mph) and striking the sternum at the level of the fourth intercostal space. Additional questions persist concerning whether the anterior and posterior regions of the chest behave as highly damped masses or oscillate after impact, the relationship between force delivered to the surface of the body and the acceleration of the underlying regions, and the influence of air compressed in the lung on thoracic mechanics.
Experiments were performed, using the carcasses of freshly sacrificed swine (sus scrofa), on which accelerometers were fastened to the sternum and backbone at the level of the fourth intercostal space. The carcasses were then impacted by a ram in the manner of the previous cadaver work, subjected to short-duration, free-vibration impacts to the sternum, and dropped into a shallow pool of water from heights up to 9.1 m (30 ft) to simulate the severe frontal impact sustained by a stunt diver. The acceleration ratios were noted, and the acceleration traces were integrated to obtain chest deflection and Fourier analyzed for harmonic content. The air pressure in the lung was also monitored during one series of ram and free-vibration experiments.

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