Pulmonary perfusion with dynamic PEEP recruitment or sustained inflation at birth in preterm lambs.

Abstract

Sustained inflation (SI) and dynamic PEEP recruitment (dynPEEP) aim to facilitate preterm lung aeration, but the effect of dynPEEP on pulmonary arterial (PA) blood flow after birth is unknown. Preterm (128 ± 1 day) fetal lambs instrumented with left PA and ductus arteriosus flow probes underwent positive-pressure ventilation (PEEP 8 cmH₂O) after early cord clamping, preceded by either (1) SI at 40 cmH₂O for 35 ± 3 s (n = 7) or (2) dynPEEP (n = 9) over 275 ± 23 s, comprising 2 cmH₂O step rises in PEEP from 6 to 18 cmH₂O followed by 2 cmH₂O decrements to 6 cmH₂O PEEP, then lung re-recruitment at 18 cmH₂O PEEP. Hemodynamics were recorded for 30 min after birth. During dynPEEP, PA blood flow increased linearly (P < 0.001) except for plateaus (1) between 12 cmH₂O PEEP on the escalation limb and 14 cmH₂O PEEP on the de-escalation limb, and (2) during lung re-recruitment. By contrast, PA flow increased during SI (P < 0.02), and was then briefly unchanged before rising linearly (P < 0.001). Consequently, post-birth rises in PA flow diverged between groups (P < 0.001), with this flow lower during dynPEEP by lung re-recruitment (P ≤ 0.048), but subsequently similar between groups. Only transient temporal differences in PA blood flow occur between SI and dynPEEP lung recruitment maneuvers at birth. This study shows that a dynamic escalation and de-escalation positive end-expiratory pressure (PEEP) lung recruitment maneuver applied during the phase of rapidly-increasing pulmonary blood flow in the immediate period after preterm birth does not impede the peak of this flow increase, although transient plateauing of pulmonary flow occurs at high levels of PEEP This response contrasts with a sustained reduction of pulmonary blood flow reported during and after elevations in PEEP following stabilization of increased pulmonary perfusion after birth This preclinical study provides evidence that dynamic PEEP lung recruitment immediately after birth does not impair subsequent pulmonary perfusion.