Head Injury and Lung Compliance

Abstract

The present experiments were carried out in order to evaluate the influence of head injury on lung compliance as determined by in vivo methods. Lethal or ‘sub-lethal’ head injury in monkeys did not alter gross lung appearance but caused a 36-percent in vivo compliance decrease. This compliance decrease was not ameliorated with isoproterenol which tends to eliminate airway smooth muscle involvement. Systemic hemodynamic causal factors were reasonably ruled out in at least three animals by maintenance of constant aortic and central vena cavai pressures.

Pulmonary Effects of Prolonged Sympathetic Stimulation

“…The initial compliance decrease is apparently not due to systemic hemodynamic factors, as suggested by only a minimal rise in pulmonary artery and left atrial pressures (1-3 mm Hg) during stimulation of the pulmonary sympathetics in cats (10). Previous findings (9) showed that lung compliance decreases and altered surfactants occurred immediately after mechanical head injury in the absence of gross lung pathology. These compliance decreases were blocked by various sympathetic agents ( 9 ) , as was also the decrease found after stress from exposure to hyperbaric oxygen ( 1 2 ) .…”

“…Previous findings (9) showed that lung compliance decreases and altered surfactants occurred immediately after mechanical head injury in the absence of gross lung pathology. These compliance decreases were blocked by various sympathetic agents ( 9 ) , as was also the decrease found after stress from exposure to hyperbaric oxygen ( 1 2 ) . In view of such findings, it is not surprising that stimulation of the pulmonary sympathetics via the stellate ganglion in cats resulted in a decreased lung compliance in the absence of pulmonary congestion and edema even after prolonged continuous stimulation.…”

“…Similar fi'ndi'ngs in animals exposed to experimental head injury (4-7), hyperbaric oxygen (8), and sympathetic nerve stimulation suggest that, in addition to possible hemodynamic changes, the sympathetics may alter the alveolar surfactants prior to the subsequent development of pulmonary congestion and edema (9,10). Previous work has shown that shortterm stimulation of the sympathetics results immediately in a decreased lung compliance and altered surfactants in the absence of any initial gross lung injury (lo), as evidenced by normal or even decreased lung wt/body wt ratios.…”

“…The present experiments indicate that prolonged continuous sympathetic nerve stimulation results in a decrease in lung compliance in the absence of any significant pulmonary congestion and edema, as shown by normal lung wt/body wt ratios, normal wet wt/dry wt ratios and the absence of any gross pathology. Previous work suggested that the initial compliance decrease during sympathetic nerve stimulation is due to an alteration in the alveolar surfactants (9). These subsequent changes may also be a result of surfactant changes.…”