The preterm infant : evaluating and developing non-invasive respiratory strategies to avoid mechanical ventilation

Sammanfattning: Avoiding mechanical ventilation of preterm infants is important to prevent morbidity and mortality. Non-invasive ventilation and CPAP has been shown to be superior to intubation and mechanical ventilation in preventing chronic lung disease in very preterm infants.1 . CPAP for infants was first used in the early 70’s. Since then, several different CPAP devices have been developed. Some of them are designed to give long term respiratory support while others are designed for initial support, with the possibility to give positive pressure ventilation (PPV) if needed. Some are expensive and complicated with several add on features while other are cheap, with simple mechanisms and easy to use. The goal for CPAP treatment is to give continuous airway pressure to the infants in order to minimize the work of breathing and improve gas exchange. But are all CPAP systems the same? Do all CPAP systems deliver stable airway pressure which helps the infants with their work of breathing? The overall aim of this thesis was to evaluate existing and newly developed devices for noninvasive respiratory support used in neonates in the DR and the NICU. The focus was on device resistance, pressure stability, imposed work of breathing and interfaces used. The aim of Paper I was to examine the in vitro performance of a new system (rPAP) and to perform a clinical feasibility trial, comparing a T-piece system with face mask, and the new system with face mask or nasal prongs, for initial stabilization of preterm infants. The new device was shown in a mechanical lung model to be pressure stable and have low imposed work of breathing compared to the T-piece. The feasibility trial comparing these devices revealed no safety issues when stabilizing preterm infants with the new device. The aim of Paper II was to examine the in vitro performance of the Medijet CPAP reusable and disposable generators and compare them to other CPAP systems. The main mechanism of CPAP generation for the disposable Medijet generator was shown to be resistance. The Medijet systems shows increasing resistance to breathing with each design generation. Our results suggest that the disposable Medijet should be used cautiously in patients where lowresistance and pressure-stable CPAP is believed to be clinically important. The aim of Paper III was to compare the revised Pumani CPAP system with two traditional bubble CPAP systems, focusing on in-vitro performance and safety. The revised Pumani system had high resistance, high imposed work of breathing and submersion depth had almost no impact on the delivered pressure which is the main CPAP generating mechanism of true bubble CPAP systems. The aim of Paper IV was to evaluate if using the new system (rPAP) with nasal prongs as interface, could reduce the need for intubation of extremely preterm infants in the DR compared to using the standard T-piece system with face mask. The CORSAD randomized controlled trial showed that using the new system decreased delivery room intubations in extremely preterm infants and creates thereby a possibility to avoid mechanical ventilation.