A Trial Comparing Noninvasive Ventilation Strategies in Preterm Infants Following Extubation

Overview

Respiratory distress syndrome (RDS) is the main cause of respiratory failure in preterm neonates, its incidence varying from 80% to 25% depending on gestational age.When optimal prenatal care is provided, the best approach to treat RDS, according to several recent trials,consists in providing continuous positive airway pressure (CPAP) from the first minutes of life using short binasal prongs or masks, followed by early selective surfactant administration for babies with worsening oxygenation and/or increasing work of breathing. Any effort should be done to minimize the time under invasive mechanical ventilation (IMV).Nonetheless, clinical trials have shown that a relevant proportion of preterm neonates fails this approach and eventually need IMV.The duration of IMV is a well known risk factor for the development of broncho-pulmonary dysplasia (BPD) - a condition associated with significant morbidity and mortality. To minimize the duration of IMV, various non invasive respiratory support modalities are available in neonatal intensive care units (NICU). CPAP is presently the most common technique used in this regard. However, a systematic review has shown that non-invasive positive pressure ventilation (NIPPV) reduces the need for IMV (within one week from extubation) more effectively than NCPAP, although it is not clear if NIPPV may reduce need for intubation longterm and it seems to have no effect on BPD and mortality. NIPPV main drawback is the lack of synchronization, which is difficult to be accurately achieved and is usually unavailable. A more recent alternative technique is non-invasive high frequency oscillatory ventilation (NHFOV) which consists on the application of a bias flow generating a continuous distending positive pressure with oscillations superimposed on spontaneous tidal breathing with no need for synchronization. The physiological, biological and clinical details about NHFOV have been described elsewhere. To date, there is only one small observational uncontrolled study about the use of NHFOV after extubation in preterm infants. Other relatively small case series or retrospective cohort studies suggested safety, feasibility and possible usefulness of NHFOV and have been reviewed elsewhere.The only randomized trial published so far compared NHFOV to biphasic CPAP,in babies failing CPAP and it has been criticized for methodological flaws and for not taking into account respiratory physiology.An European survey showed that, despite the absence of large randomized clinical trials, NHFOV is quite widely used, at least in some Countries and no major side effects are reported, although large data about NHFOV safety are lacking. This may be due to the relative NHFOV easiness of use but evidence-based and physiology-driven data are warranted about this technique.

NHFOV should theoretically provide the advantages of invasive high frequency oscillatory ventilation (no need for synchronization, high efficiency in CO2 removal, less volume/barotrauma) and nasal CPAP (non-invasive interface, oxygenation improvement by the increase in functional residual capacity through alveolar recruitment). NHFOV should allow to increase mean airway pressure (Paw) avoiding gas trapping and hypercarbia, thanks to the superimposed high frequency oscillations. Therefore, NHFOV is more likely to be beneficial for those neonates requiring high distending pressure to open up their lungs, such as babies at high risk of extubation failure due to severity of their lung disease. This may also be the case of extremely preterm, BPD-developing neonates who have increased airway resistances, while they are subjected to a deranged alveolarization and lung growth. Neonates presenting with respiratory acidosis may also benefit from NHFOV. Several animal and bench studies investigated the physiology and peculiarities of NHFOV and these data should be used to conduct a physiology-guided trial in order to avoid errors done in the early trials about invasive high frequency ventilation. This study will be the first large trial aiming to compare CPAP vs NIPPV vs NHFOV in preterm neonates after surfactant replacement and during their entire NICU stay, to reduce the total need of invasive ventilation. Since there is a lack of formal data regarding NHFOV safety, some safety outcomes will also be considered.Specific subgroup analysis will be conducted for pre-specified groups of patients who may most likely benefit from NHFOV, according to the above-described physiological characteristics.