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

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.

Eighteen preterm infants (gestational age = 29-36 week) were randomized to receive either continuous positive airway pressure (CPAP) at 5 cmH₂ O only or combined with a sustained inflation (SI; 15 seconds at 25 cmH₂ O 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 cmH₂ O*s/L) and higher (higherX_5,i ; X₅  > -240 cmH₂ O*s/L) initial degree of lung volume recruitment.

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 cmH₂ O vs -274 ± 58 cmH₂ O). 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.

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.