PRESERVATION OF PULMONARY-FUNCTION IN THE VENTILATED NEONATAL PIGLET WITH NORMAL LUNGS

Little attention has been focused on the progressive pulmonary deterio ration which occurs in mechanically ventilated infants with normal or mildly abnormal lungs. We hypothesized that lung function would deteri orate over a 24-hr period in anesthetized neonatal piglets with normal lungs mechanically ventilated at 2 cm H2O PEEP (2PEEP group). We furt her hypothesized that an intermittent lung inflation procedure consist ing 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) w ould prevent this deterioration in lung function, similar to piglets m echanically ventilated continuously at 6 cm H2O PEEP (6PEEP). Results indicate that 2PEEP piglets experienced progressive deterioration in l ung function, including dynamic lung compliance (-42%) and lung resist ance (+55%). In contrast, Inflation piglets and 6PEEP piglets had no d eterioration in lung function. Hemodynamics were similar between group s, although they were the most stable in the 6PEEP group. Histopatholo gical changes were not significantly different. We conclude that (1) p rolonged mechanical ventilation at 2 cm H2O PEEP in neonatal piglets r esulted in progressive deterioration in pulmonary function, (2) interm ittent lung inflation or continuous 6 cm H2O PEEP prevented deteriorat ion, and (3) functional changes occurred without changes in histopatho logy. 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 n ormal lungs. (C) 1995 Wiley-Liss, Inc.