• Ximena Alegría, Nelson Claure, Yoshirou Wada, Cristian Esquer, Carmen D'Ugard, and Eduardo Bancalari.
• Department of Pediatrics, Division of Newborn Medicine, University of Miami Miller School of Medicine, Miami, Florida 33101, USA.
• Pediatr. Pulmonol. 2006 Aug 1; 41 (8): 759-64.

BackgroundPositive end expiratory pressure (PEEP) is routinely used in mechanically ventilated preterm infants to maintain lung volume. An acute increase in PEEP can affect lung mechanics and tidal volume, but it is unknown if these effects elicit compensatory changes in respiratory center output.ObjectivesTo investigate the acute effects of changes in PEEP on tidal volume (V(T)), lung compliance (C(L)), and respiratory center output (RCO) during synchronized intermittent mandatory ventilation (SIMV) in preterm infants at different levels of basal respiratory drive.MethodsPreterm infants were studied during SIMV at three levels of PEEP (2, 4, and 6 cm H(2)O for 2-3 min each) and at two levels of inspired CO(2). Peak inspiratory pressure (PIP) was adjusted to maintain the same delta pressure at the airway. RCO was assessed by measuring total diaphragmatic electrical activity. The level of inspired CO(2) was adjusted by modifying the instrumental dead space.ResultsSixteen preterm infants GA: 25 +/- 2 weeks, BW: 786 +/- 242 g, age: 18 +/- 15 days, SIMV: rate 14 +/- 3 b/min, Ti: 0.35 +/- 0.01 s, PIP: 16 +/- 1 cm H(2)O, and FiO(2): 0.31 +/- 0.06 were studied. At both levels of inspired CO(2), C(L), V(T), and V'(E) from spontaneous and mechanical breaths decreased significantly with higher PEEP. RCO did not change, but at lower respiratory drive, there was a trend towards an increase in RCO with higher PEEP.ConclusionHigher PEEP levels can have acute negative effects on lung mechanics and ventilation in preterm infants without a sufficient compensatory increase in RCO.

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