Newborn respiratory support using distending pressure : the effect of interfaces and system design on performance and outcome

Abstract

Preterm infants often require respiratory support after birth due to lung immaturity. The preferred method of providing respiratory support to breathing infants in respiratory distress is non-invasively with continuous positive airway pressure (CPAP). This has been associated with less mortality and morbidity compared to invasive mechanical ventilation. The continuous distending pressure that improves lung aeration and gas exchange can be generated with different CPAP systems and is usually applied through either nasal mask or prongs in the neonatal intensive care unit while face mask has been the most used interface in the delivery room.

The overall aim of this thesis was to evaluate how different interfaces and system design affect the quality and outcome of CPAP respiratory support for neonates in the delivery room and neonatal intensive care unit. In study I the literature was reviewed regarding differences in bubble CPAP systems intended for use in low-resource settings. Tests in a mechanical lung model showed how using an interface with high resistance or expiratory tubing with a narrow diameter can lead to increased imposed work of breathing and higher delivered mean airway pressure. Study II was a randomised clinical cross-over study with the aim of measuring leakage during CPAP treatment in newborn infants with nasal mask versus nasal prongs. Measurements revealed a greater leakage for nasal mask compared with prongs. Although some leakage was common with both interfaces it could often be reduced with simple care adjustments. Study III was a follow up study of extremely preterm infants included in the randomised CORSAD study in Stockholm. Medical records of the infants that had been randomised to initial respiratory support with either rPAP using nasal prongs or T-piece with face mask were reviewed up to 36 weeks of postmenstrual age. Infants in the rPAP group were less likely to be intubated and receive mechanical ventilation during the first week of life. At 36 weeks of postmenstrual age there was no statistically significant difference found in mortality or bronchopulmonary dysplasia. Study IV was a feasibility study evaluating a simplified version of the rPAP system for delivery room stabilisation and continued support during transportation and after arrival in the neonatal unit. The system could be used for stabilisation both skin-to-skin and on a resuscitation table as well as for continued support the first hours after birth. The study did not reveal problems with the system or safety.