LAUSR

Airway management is important in trauma and critically ill patients. Prolonged mechanical ventilation results in over-ventilation induced lung barotrauma, but few studies have examined the consequence of acute (1 h or less) over-ventilation. We hypothesized that acute hyperventilation, as might inadvertently be performed in pre-hospital settings, would elevate systemic inflammation and cause lung damage. Female Yorkshire pigs (40-50 kg, n=10/group) were anesthetized, instrumented for hemodynamic measurements and blood sampling, and. underwent a 25% controlled hemorrhage followed by 1 h of: 1) spontaneous breathing; 2) "normal" bag ventilation (4.8 L minute volume, ~400 mL tidal volume, 12 breaths/minute); 3) bag hyperventilation (9 L minute volume, ~750 mL tidal volume, 12 breaths/minute); 4) maximum hyperventilation (15 L minute volume, ~~750 mL tidal volume, 20 breaths/minute); or, 5) mechanical ventilation. Pigs then regained consciousness and recovered for 24 hrs, followed by euthanasia and collection of blood and tissue samples. No level of manual ventilation had any significant impact on hemodynamic variables. Blood markers of tissue damage and plasma cytokines were not statistically different between groups with the exception of a transient increase in IL-1β; all values returned to baseline by 24 hrs. On pathological review, severity and distribution of lung edema or other gross pathologies were not significantly different between groups. These data indicate hyperventilation causes no adverse effects, to include inflammation and tissue damage; and that acute over-ventilation, as could be seen in the pre-hospital phase of trauma care, does not produce evidence of adverse effects on the lungs following moderate hemorrhage.