In-vitro Bench Evaluation of a Novel Adjus-Amplitude Bubble CPAP System for Neonatal Respiratory Support

Abstract

Respiratory distress syndrome (RDS) in preterm neonates remains a major contributor to neonatal mortality worldwide, with
India bearing a disproportionate share of the global preterm birth burden, over 3 million births annually, more than 20% of
the global total. Bubble continuous positive airway pressure (B-CPAP) is a widely used, low-cost mode of non-invasive
respiratory support for these infants, but in every existing design, oscillatory amplitude is mechanically coupled to bias flow
and therefore to the mean delivered pressure. Therefore, clinicians cannot raise one without raising the other. Humming BEE
B-CPAP system decouples these variables through an independently controlled secondary extra-flow channel introduced into
an enlarged bubble-generating chamber, conceptually importing an amplitude-control variable analogous to high-frequency
oscillatory ventilation (HFOV) into the bubble CPAP platform.
In-vitro bench testing was performed using calibrated airway-pressure transducer and oscilloscope-based measurements across
a range of bias-flow (5–8 L/min) and extra-flow (0–14 L/min) settings at a fixed CPAP set point of 5 cm H₂O. Introducing
graded extra flow produced an approximately monotonic rise in oscillatory pressure amplitude of roughly 70 to 100% while
delivered CPAP remained at its set point across the majority of conditions tested. Dominant oscillation frequency rose initially
with extra flow before falling at higher settings, consistent with progressive bubble coalescence and the Minnaert relationship,
yielding a favorable high-amplitude, reduced-frequency operating point at the upper end of the extra-flow range.
Preliminary observational clinical experience of Humming Bee B-CPAP in approximately 50 neonates with RDS has suggested
that the device is feasible and well tolerated in routine neonatal practice.
These findings support a physiological rationale, grounded in bubble dynamics and HFOV principles, for why this capability may
aid CO₂ clearance in neonates, particularly those with borderline rising PaCO₂ or in the acute low-compliance phase of RDS.