title: Sustained inflation at birth did not protect preterm fetal sheep from lung injury.
abstract: Sustained lung inflations (SI) at birth may recruit functional residual capacity (FRC). Clinically, SI increase oxygenation and decrease need for intubation in preterm infants. We tested whether a SI to recruit FRC would decrease lung injury from subsequent ventilation of fetal, preterm lambs. The preterm fetus (128±1 day gestation) was exteriorized from the uterus, a tracheostomy was performed, and fetal lung fluid was removed. While maintaining placental circulation, fetuses were randomized to one of four 15-min interventions: 1) positive end-expiratory pressure (PEEP) 8 cmH2O (n=4), 2) 20 s SI to 50 cmH2O then PEEP 8 cmH2O (n=10), 3) mechanical ventilation at tidal volume (VT) 7 ml/kg (n=13), or 4) 20 s SI then ventilation at VT 7 ml/kg (n=13). Lambs were ventilated with 95% N2/5% CO2 and PEEP 8 cmH2O. Volume recruitment was measured during SI, and fetal tissues were collected after an additional 30 min on placental support. SI achieved a mean FRC recruitment of 15 ml/kg (range 8-27). Fifty percent of final FRC was achieved by 2 s, 65% by 5 s, and 90% by 15 s, demonstrating prolonged SI times are needed to recruit FRC. SI alone released acute-phase proteins into the fetal lung fluid and increased mRNA expression of proinflammatory cytokines and acute-phase response genes in the lung. Mechanical ventilation further increased all markers of lung injury. SI before ventilation, regardless of the volume of FRC recruited, did not alter the acute-phase and proinflammatory responses to mechanical ventilation at birth.
authors.affiliation: Saint Louis Univ., Cardinal Glennon-Neonatology, 1100 South Grand, Saint Louis, MO 63104. Hillman@slu.edu.
authors.forename: Noah H
authors.initials: NH
authors.lastname: Hillman
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Kemp
authors.forename: Peter B
authors.initials: PB
authors.lastname: Noble
authors.forename: Suhas G
authors.initials: SG
authors.lastname: Kallapur
authors.forename: Alan H
authors.initials: AH
authors.lastname: Jobe
mesh_terms: D000210:Acute-Phase Reaction / Q000378:metabolism; D000818:Animals; D005260:Female; D005652:Functional Residual Capacity; D055370:Lung Injury / Q000517:prevention & control*; D011175:Positive-Pressure Respiration; D011247:Pregnancy; D047928:Premature Birth / Q000503:physiopathology*; D012121:Respiration, Artificial; D034561:Sheep, Domestic
keywords: bronchopulmonary dysplasia; functional residual capacity; inflammation; resuscitation