Dynamic lung aeration after birth does not impede pulmonary blood flow in preterm lambs.

RATIONALE: Stepwise positive end-expiratory pressure at birth (dynamic PEEP) reduces lung injury in preterm lambs; however, the impact of dynamic PEEP on pulmonary blood flow (PBF) during immediate (ICC) and deferred cord clamping (DCC) is unknown.

OBJECTIVES

To determine the impact of dynamic PEEP on PBF during DCC and ICC.

METHODS

Preterm lambs (n=22) received a ventilation strategy with either dynamic PEEP (between 8 and 14 cmH2O) or static PEEP (8 cmH2O) after birth. Lambs were managed with either DCC or ICC (30 s clamp to ventilation) (n=5-6 per group). Left pulmonary artery flow was measured using echocardiography as a surrogate for PBF. Ventilation parameters and PBF were measured every 20 s until 180 s and at 5, 10 and 15 min from ventilation onset.

RESULTS

There was no significant difference in PBF between dynamic and static PEEP applied during DCC (mean (SD) 183 (66) vs 125 (43) mL/kg/min, mean (SD) difference=-58 (103) mL/kg/min, p=0.09) or ICC (124 (26) vs 120 (31) mL/kg/min, mean difference=-4(184), p=0.94). PBF significantly increased over time (p<0.01; mixed effects) in all groups regardless of cord management. This was associated with an increase in the velocity time integral (p<0.01) but no difference in heart rate. Cerebral blood flow reduced over time during DCC (p<0.01) with no change observed during ICC. There was no difference in lung mechanics apart from higher respiratory system compliance in the ICC Dynamic PEEP group (mean difference 0.08 (0.05) mL/kg/cmH2O, p<0.01).

CONCLUSIONS

Elective lung recruitment after birth using a dynamic PEEP does not impede PBF in preterm lambs.