Dynamic factors influencing the production of lung injury in rabbits subjected to blunt chest wall impact.

Anesthetized rabbits were exposed to blunt impact on the right chest wall. The controlled impact was delivered with a special machine equipped with a captive piston driven by a freely falling weight. Chest wall deflections were recorded in order to study the effects of magnitude and rate of deformation of the thorax on the resulting lung injury. The ranges of magnitude and rate of deformation corresponded to an inward deflection of the chest wall of about 5-60% of the lateral diameter of the chest, and to a velocity of the chest wall of about 2-20 m/s. Impulses delivered to the chest and intrathoracic pressures were also studied. Severe hemorrhages in the lungs were produced at velocities of the chest wall exceeding about 10 m/s. For velocities of the chest wall below about 5 m/s, lethal injuries were produced without severe hemorrhages in the lungs.