Preservation of pulmonary function in the ventilated neonatal piglet with normal lungs.

Little attention has been focused on the progressive pulmonary deterioration which occurs in mechanically ventilated infants with normal or mildly abnormal lungs. We hypothesized that lung function would deteriorate over a 24-hr period in anesthetized neonatal piglets with normal lungs mechanically ventilated at 2 cm H2O PEEP (2PEEP group). We further hypothesized that an intermittent lung inflation procedure consisting of 15 out of 60 min of increasing lung distention (4, 8, 12 cm H2O PEEP), with the remaining 45 min at 2 cm H2O PEEP (Inflation group) would prevent this deterioration in lung function, similar to piglets mechanically ventilated continuously at 6 cm H2O PEEP (6PEEP). Results indicate that 2PEEP piglets experienced progressive deterioration in lung function, including dynamic lung compliance (-42%) and lung resistance (+55%). In contrast, inflation piglets and 6PEEP piglets had no deterioration in lung function. Hemodynamics were similar between groups, although they were the most stable in the 6PEEP group. Histopathological changes were not significantly different. We conclude that (1) prolonged mechanical ventilation at 2 cm H2O PEEP in neonatal piglets resulted in progressive deterioration in pulmonary function, (2) intermittent lung inflation or continuous 6 cm H2O PEEP prevented deterioration, and (3) functional changes occurred without changes in histopathology. Lung inflation strategies other than PEEP can be used to prevent deterioration in lung function which accompanies prolonged mechanical ventilation in anesthetized nonspontaneously breathing piglets with normal lungs.