Objective In an attempt to reduce the work of breathing (WOB) and the risk of respiratory failure, preterm infants are increasingly treated with nasal synchronised biphasic positive airway pressure (BPAP) via the Infant Flow SiPAP system. However, the relatively high resistance of the generator limits the pressure amplitude (PA) and pressure build-up (PB) of this system. This in vitro study investigates the impact of a new generator with improved fluid mechanics on the WOB, PA and PB during BPAP.

Methods Using a low compliance lung model, WOB, PA and PB, were measured during BPAP using the old and the new Infant Flow generators. Airway resistance (tube sizes 2.5 mm, 3.0 mm and 3.5 mm), nasal interface sizes (small, medium and large) and four different ventilator settings were used to mimic different clinical conditions.

Results Compared with the old generator, the new generator significantly reduced the WOB between 10% and 70%, depending on the measurement configuration. The maximum PA was higher when using the new (6–7 cm H₂O) generator versus the old (3–4 cm H₂O) generator. During the first 100 ms of inspiration, the new generator reached between 33% and 40% of the peak pressure compared with 11–20% for the old generator.

Conclusions This in vitro study shows that a new generator of the Infant Flow SiPAP device results in a significant reduction in WOB and an increase in PA and PB during BPAP. The results of this study need to be confirmed under variable clinical conditions in preterm infants.