High-CPAP Does Not Impede Cardiovascular Changes at Birth in Preterm Sheep.

Continuous positive airway pressures (CPAP) used to assist preterm infants at birth are limited to 4-8 cmHO due to concerns that high-CPAP may cause pulmonary overexpansion and adversely affect the cardiovascular system. We investigated the effects of high-CPAP on pulmonary (PBF) and cerebral (CBF) blood flows and jugular vein pressure (JVP) after birth in preterm lambs. Preterm lambs instrumented with flow probes and catheters were delivered at 133/146 days gestation. Lambs received low-CPAP (LCPAP: 5 cmHO), high-CPAP (HCPAP: 15 cmHO) or dynamic HCPAP (15 decreasing to 8 cmHO at ~2 cmHO/min) for up to 30 min after birth. Mean PBF was lower in the LCPAP [median (Q1-Q3); 202 (48-277) mL/min, = 0.002] compared to HCPAP [315 (221-365) mL/min] and dynamic HCPAP [327 (269-376) mL/min] lambs. CBF was similar in LCPAP [65 (37-78) mL/min], HCPAP [73 (41-106) mL/min], and dynamic HCPAP [66 (52-81) mL/min, = 0.174] lambs. JVP was similar at CPAPs of 5 [8.0 (5.1-12.4) mmHg], 8 [9.4 (5.3-13.4) mmHg], and 15 cmHO [8.6 (6.9-10.5) mmHg, = 0.909]. Heart rate was lower in the LCPAP [134 (101-174) bpm; = 0.028] compared to the HCPAP [173 (139-205)] and dynamic HCPAP [188 (161-207) bpm] groups. Ventilation or additional caffeine was required in 5/6 LCPAP, 1/6 HCPAP, and 5/7 dynamic HCPAP lambs ( = 0.082), whereas 3/6 LCPAP, but no HCPAP lambs required intubation ( = 0.041), and 1/6 LCPAP, but no HCPAP lambs developed a pneumothorax ( = 0.632). High-CPAP did not impede the increase in PBF at birth and supported preterm lambs without affecting CBF and JVP.