Role of impact velocity and chest compression in thoracic injury.

Impact velocity and chest compression are important factors in traumatic injury; however, there is no functional relationship to assess impact severity. A blunt thoracic impact of constant velocity (5-22 m/s) and prescribed contact displacement (3-46 mm) was delivered to 123 anesthetized rabbits. Myocardial and major vascular injury increased from contusion to rupture with cardiac tamponade and sudden death as either impact velocity or chest compression was independently increased. A theoretical relationship was found for impact severity: IS=VC/1-C, where V and C are impact velocity and normalized chest compression. Based on the frequency of critical/fatal injury, probit analysis gave IS=6.4 m/s as an estimate of the ED50 response in the experimental model.