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

Tessa Martherus,Calum T Roberts,Graeme R Polglase,Kelly J Crossley,Alison M Moxham,Stuart B Hooper,Janneke Dekker,Valerie A Zahra,Arjan B Te Pas,Karyn A Rodgers,Anja Demel

doi:10.3389/fped.2020.584138

Abstract

Objective: Continuous positive airway pressures (CPAP) used to assist preterm infants at birth are limited to 4–8 cmH2O 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.Methods: Preterm lambs instrumented with flow probes and catheters were delivered at 133/146 days gestation. Lambs received low-CPAP (LCPAP: 5 cmH2O), high-CPAP (HCPAP: 15 cmH2O) or dynamic HCPAP (15 decreasing to 8 cmH2O at ~2 cmH2O/min) for up to 30 min after birth.Results: Mean PBF was lower in the LCPAP [median (Q1–Q3); 202 (48–277) mL/min, p = 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, p = 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 cmH2O [8.6 (6.9–10.5) mmHg, p = 0.909]. Heart rate was lower in the LCPAP [134 (101–174) bpm; p = 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 (p = 0.082), whereas 3/6 LCPAP, but no HCPAP lambs required intubation (p = 0.041), and 1/6 LCPAP, but no HCPAP lambs developed a pneumothorax (p = 0.632).Conclusion: High-CPAP did not impede the increase in PBF at birth and supported preterm lambs without affecting CBF and JVP.

Highlights

Respiratory support for preterm infants at birth has shifted from intubation and mechanical ventilation toward non-invasive strategies [1,2,3,4]
We investigated the effects of high-continuous positive airway pressure (CPAP) on pulmonary (PBF) and cerebral (CBF) blood flows and jugular vein pressure (JVP) after birth in preterm lambs
High-CPAP did not impede the increase in pulmonary blood flow (PBF) at birth and supported preterm lambs without affecting cerebral blood flow (CBF) and JVP

Summary

Introduction

Respiratory support for preterm infants at birth has shifted from intubation and mechanical ventilation toward non-invasive strategies [1,2,3,4]. When applied non-invasively, intermittent positive pressure ventilation (iPPV) is unable to ventilate the lung if the larynx is closed, which is known to occur in the fetus and newborn during apnea [5,6,7,8]. High-CPAP at Preterm Birth has focused on stimulating and supporting spontaneous breathing at birth using continuous positive airway pressure (CPAP) [9,10,11]. This has highlighted a knowledge gap regarding how CPAP should be applied in the delivery room. Lung aeration triggers a decrease in pulmonary vascular resistance (PVR) and increase in PBF [19, 20], which is critical for the maintenance of cardiac output after birth, as PBF must take over the role of providing preload for the left ventricle following cord clamping [17]

Methods

Results

Conclusion