Previous clinical studies have shown that pulmonary complications may attend mechanical trauma, including injuries resulting from car crashes involving the head, thorax, and the extremities. Autopsy reports of car crash victims in some cases show gross pulmonary hemorrhage and edema.

An investigation was carried out using the primate as a model to determine the type and extent of any immediate pulmonary changes following exposure to experimental mechanical trauma, and to consider the causal factors involved. One hundred squirrel monkeys were exposed to controlled mechanical head injury and the compliance of the excised lungs decreased by 40-60% in these traumatized primates. Additional experiments with rhesus monkeys supported this work. These pulmonary effects are attributed primarily to an alteration in lung surface tension forces mediated by the sympathetics as shown by the effect of various blocking agents on these lung changes.

Results of an analysis of clinical and some laboratory data suggest that direct pulmonary complications in addition to any possible airway obstruction occurs immediately following trauma in car crash victims and may result in increased mortality rates.