Bi-level CPAP does not change central blood flow in preterm infants with respiratory distress syndrome

BACKGROUND: Current literature provides limited data on the hemodynamic changes that may occur during bi-level continuous positive airway pressure (CPAP) support in preterm infants. However, the application of a positive end-expiratory pressure may be transmitted to the heart and the great vessels resulting in changes of central blood flow. OBJECTIVE: To assess changes in central blood flow in infants with respiratory distress syndrome (RDS) during bi-level CPAP support. DESIGN: A prospective study was performed in a cohort of 18 Very-Low-Birth-Weight Infants who were put on nasal CPAP support (4-5 cmH2O) because they developed RDS within the first 24-72 hours of life. Each subject was switched to bi-level CPAP support (Phigh 8 cmH2O, Plow 4-5 cmH2O, Thigh 0.5-0.6 seconds, 20 breaths/min) for an hour. An echocardiographic study and a capillary gas analysis were performed before and after the change of respiratory support. RESULTS: No differences between n-CPAP and bi-level CPAP in left ventricular output (LVO, 222.17 ± 81.4 vs 211.4 ± 75.3 ml/kg/min), right ventricular output (RVO, 287.8 ± 96 vs 283.4 ± 87.4 ml/kg/min) and superior vena cava flow (SVC, 135.38 ± 47.8 vs 137.48 ± 46.6 ml/kg/min) were observed. The hemodynamic characteristics of the ductus arteriosus were similar. A significant decrease in pCO2 levels after bi-level CPAP ventilation was observed; pCO2 variations did not correlate with modifications of central blood flow (LVO: ρ=0.11, p=0,657; RVO: ρ=-0.307, p=0.216; SVC: ρ=-0.13, p=0.197). CONCLUSIONS: Central blood flow doesn't change during bi-level CPAP support, which could become a hemodinamically safe tool for the treatment of RDS in preterm infants.