Changes in respiratory mechanics at birth in preterm infants: A pilot study

Objective: We aimed to measure lung mechanics at birth by the forced oscillation technique (FOT) for assessment of the initial degree of lung aeration and the short-term aeration changes after applying different respiratory support strategies. Methods: Eighteen preterm infants (gestational age = 29-36 week) were randomized to receive either continuous positive airway pressure (CPAP) at 5 cmH₂O only or combined with a sustained inflation (SI; 15 seconds at 25 cmH₂O after 5 seconds of CPAP) at birth. We assessed the respiratory system reactance at 5 Hz (X_5; increases with lung volume recruitment at a given distending pressure) at 2, 40, and 150 seconds after initiation of CPAP. k-Means clustering of the initial X₅ value (X_5,i) stratified newborn into either infants with lower (lowerX_5,i; X₅ < −280 cmH₂O*s/L) and higher (higherX_5,i; X₅ > −240 cmH₂O*s/L) initial degree of lung volume recruitment. Results: Initial values were highly heterogeneous. In the LowerX_5,i group, X₅ increased with time, with SI-patients showing significantly higher values at 150 seconds than the non-SI group (X₅ = −89 ± 27 cmH₂O vs −274 ± 58 cmH₂O). In the higherX_5,i group, X₅ did not improve with time, regardless of the respiratory strategy, suggesting a lack of lung recruitment. Moreover, 75% of infants receiving SI in the higherX_5,i group experienced a transient loss of aeration after the maneuver. Conclusions: Preterm newborns present initially with highly heterogeneous lung aeration at birth that significantly impacts the effectiveness of the subsequent lung volume recruitment strategy. FOT may represent a valuable tool for individualizing a respiratory resuscitation at birth as it is noninvasive and may be applied simultaneously to respiratory support.