Introduction
Preterm infants are prone to various conditions because of their immature organs. Respiratory failure related to organ immaturity is the most common cause of death in preterm infants. Invasive mechanical ventilation (IMV), which has been widely used in past decades to support neonates with respiratory failure, has many complications (air-leaks, ventilator-associated lung injury and bronchopulmonary dysplasia (BPD)) (1). Life-saving strategies that minimize injury to the lung and other organ systems, thereby reducing long-term morbidity, have been the focus of recent attention.
Given the emergence of noninvasive nasal airway interfaces for newborns, noninvasive ventilation has become a suitable technique for the treatment of neonatal respiratory diseases. The American Academy of Pediatrics and European Consensus Guidelines recommend early non-invasive ventilation for the treatment of respiratory diseases in preterm infants, citing its promising curative effects (2, 3). Noninvasive intermittent positive pressure ventilation (NIPPV) superimposes an intermittent peak pressure on continuous positive airway pressure (CPAP). The popularity of NIPPV has risen since its recent comparison to nasal CPAP, in which NIPPV significantly decreased the rates of respiratory failure, reintubation and the need for a ventilator (4). Synchronized NIPPV is the best respiratory support modality post-extubation (5), although synchronization is difficult to achieve and often unavailable. A more recent alternative is noninvasive high frequency oscillatory ventilation (NHFOV), which has the characteristics of high frequency ventilation and nasal CPAP, and does not need synchronization; it also has the advantages of being noninvasive, highly efficient in CO2 removal and has a lower volume/barotrauma (6). Compared with NIPPV and a nasal CPAP, NHFOV can reduce the need for IMV in infants treated for respiratory distress syndrome (RDS) (7). However, some RCTs have not reported a reduced intubation rate, a shortened time for oxygen therapy or non-invasive ventilator-assisted ventilation when using NHFOV versus NIPPV (8, 9). Given these conflicting findings, we conducted a comprehensive systematic review and meta-analysis to evaluate relevant evidence from published studies.