The interrelationship of recruitment maneuver at birth, antenatal steroids, and exogenous surfactant on compliance and oxygenation in preterm lambs

Background: To describe the interrelationship between antenatal steroids, exogenous surfactant, and two approaches to lung recruitment at birth on oxygenation and respiratory system compliance (C_dyn) in preterm lambs. Methods: Lambs (n = 63; gestational age 127 ± 1 d) received either surfactant at 10-min life (Surfactant), antenatal corticosteroids (Steroid), or neither (Control). Within each epoch lambs were randomly assigned to a 30-s 40cmH₂O sustained inflation (SI) or an initial stepwise positive end-expiratory pressure (PEEP) open lung ventilation (OLV) maneuver at birth. All lambs then received the same management for 60-min with alveolar-arterial oxygen difference (AaDO₂) and C_dyn measured at regular time points. Results: Overall, the OLV strategy improved C_dyn and AaDO₂ (all epochs except Surfactant) compared to SI (all P < 0.05; two-way ANOVA). Irrespective of strategy, C_dyn was better in the Steroid group in the first 10 min (all P < 0.05). Thereafter, C_dyn was similar to Steroid epoch in the OLV + Surfactant, but not SI + Surfactant group. OLV influenced the effect of steroid and surfactant (P = 0.005) on AaDO₂ more than SI (P = 0.235). Conclusions: The antenatal state of the lung influences the type and impact of a recruitment maneuver at birth. The effectiveness of surfactant maybe enhanced using PEEP-based time-dependent recruitment strategies rather than approaches solely aimed at initial lung liquid clearance.