Ventilation-mediated injury after preterm delivery of Ureaplasma parvum colonized fetal lambs.

Ureaplasma species are the microorganisms most frequently isolated from women with preterm birth and are associated with an increased risk of bronchopulmonary dysplasia. Initiation of ventilation with high tidal volumes (VT) causes lung injury and inflammation. We investigated whether antenatal colonization with Ureaplasma parvum serovar 3 (UP) would alter the inflammatory response to mechanical ventilation of preterm lambs. Merino ewes were given intraamniotic injections of UP at 55-d gestation, and the lambs were surgically delivered at 128+/-1 d gestation and assigned to three groups: 1) gentle ventilation (GV), 2) high VT ventilation, or 3) unventilated control. Lambs delivered from noncolonized ewes were assigned to parallel groups. GV lambs received surfactant before ventilation with a VT of 7 mL/kg, positive end expiratory pressure (PEEP) 5 cm H2O. High VT lambs received no PEEP and escalating VT to 15 mL/kg by 15 min. At 15 min, surfactant was given, VT was reduced to 7 mL/kg, and PEEP was increased to 5 cm H2O. Monocytes in bronchoalveolar lavage were increased by UP, but colonization did not affect lung function. High VT ventilation increased Egr-1 signaling, proinflammatory cytokine expression, and injury scores compared with GV. Antenatal colonization with UP did not change lung function or modulate the lung injury and inflammation caused by high VT ventilation.