![]() ![]() We hypothesized that initiation of ventilation in surfactant deficient preterm lambs using PEEP would decrease lung injury and that the injury caused by a large V T might be decreased with the use of PEEP, by minimizing collapse at end expiration. We examined how PEEP might moderate lung injury in the preterm lung to help develop recommendations for neonatal resuscitation. Volutrauma results from volumes that overstretch the lung regionally or from ventilation of collapsed lung units, and stretch induced injuries can occur in both the airways and the alveoli ( 12). Surfactant deficient fluid columns in small airways also cause fluid mechanical stresses that disrupt the airway epithelium ( 16). Atelectasis with nonuniform ventilation results in over-distension of the ventilated lung-the concept of the baby lung ( 15). Ventilation over-distends and injures the airways proximal to the atelectatic or fluid filled alveoli ( 13, 14). Ventilation of the fluid filled preterm lung has similarities to the lung injury resulting from ventilation of saline lavaged adult lungs, in that there is surfactant deficiency and fluid in the airways with atelectasis or fluid filled alveoli ( 12). In preterm sheep and baboons, CPAP decreases injury compared with mechanical ventilation without PEEP ( 10, 11). A brief period of high V T ventilation without PEEP will injure the preterm lung and subsequent ventilation with PEEP will amplify that injury ( 8) this injury can be reduced by surfactant treatment before mechanical ventilation of the preterm lung ( 4, 9). Ventilation of the preterm lung for hours without PEEP will cause lung injury and high initial V Ts further increase that lung injury ( 3, 4, 7). The equipment used for resuscitation of the preterm has not been standardized and does not allow for accurate control of tidal volume (V T), positive end-expiratory pressure/continuous positive airway pressure (PEEP/CPAP), or inspiratory times ( 5, 6). Despite the frequent need for ventilatory assistance after delivery, and numerous experimental demonstrations that the preterm lung can be easily injured by mechanical ventilation ( 3, 4), there is minimal clinical information about how best to provide initial ventilatory assistance to the preterm lung. ![]() A poor transition to air breathing in preterm infants is frequently because of surfactant deficiency, decreased respiratory drive, and perhaps more lung fluid as the majority of preterm infants are now delivered via cesarean section ( 2). This transition often requires assistance for term infants and is more difficult and ineffective for preterm infants. Critical components of this transition are clearance of fluid from the airways, establishment of a functional residual capacity (FRC), and increased blood flow to the lungs. The initiation of breathing at birth is an essential but complex adaptation that must rapidly transition the fluid filled fetal lung to gas exchange ( 1). Initial ventilation of preterm lambs with PEEP and/or V T of 8 mL/kg did not prevent an inflammatory injury to the lung. Ventilation resulted in localization of IL-6 to the small airways. Markers of lung injury were significantly elevated in all ventilation groups compared with unventilated controls no effect of PEEP was found. After the 15 min ventilation maneuver, the V T15 groups were hypocarbic, had higher oxygenation, and required lower pressures than the V T8 groups no consistent effect of PEEP was found. Lung function was assessed and measurements of lung injury were evaluated postmortem. Each group was subsequently ventilated with V T <10 mL/kg, PEEP 5 cm H 2O for 1 h 45 min. Operatively delivered preterm lambs (133 ± 1 d gestation) were randomly assigned to unventilated controls or to one of four 15 min ventilation interventions: 1) V T15 mL/kg, PEEP 0 cm H 2O 2) V T15 mL/kg, PEEP 5 cm H 2O 3) V T8 mL/kg, PEEP 0 cm H 2O and 4) V T8 mL/kg, PEEP 5 cm H 2O. We aimed to evaluate whether PEEP and/or tidal volume (V T) within the first 15-min of ventilation are protective against lung injury. Positive end-expiratory pressure (PEEP) protects the lung from injury during sustained ventilation, but its role in protecting the lung from injury during the initiation of ventilation in the delivery room is not established. ![]()
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