Dynamics analysis of neonatal CPAP devices neopuff and inspire rPAP: Investigating pressure stability and work of breathing in anatomically realistic airway models

Continuous positive airway pressure (CPAP) technology is crucial in the initial respiratory support of newborns with insufficient spontaneous breathing. Although two neonatal CPAP systems, the Neopuff T-piece and the Inspire rPAP, use constant flow technology, clinical observations reveal significant differences in pressure stability during ventilation of newborn children. The Neopuff T-piece device exhibits stronger pressure fluctuations compared to the Inspire rPAP, which maintains more stable airway pressures. This study investigates the root causes of these instabilities using computational fluid dynamics (CFD) simulations in anatomically realistic neonatal airway models, focusing on how device geometry and flow behavior influence pressure stability and imposed work of breathing (iWOB). Digital models of the devices were created using CAD software, and neonatal airway geometries were segmented from MRI data. Steady-state 3D CFD simulations, employing the k-ω-SST turbulence model, were conducted for three respiratory scenarios: resting, inhalation, and exhalation. Both CPAP devices were simulated under identical boundary conditions for direct comparison. The Inspire rPAP demonstrated higher static pressures, flow velocities, and turbulent kinetic energy (TKE) but maintained superior pressure stability, with fluctuations limited to 6.28 %, compared to 46.12 % for the Neopuff. The Neopuff's T-piece geometry generated vortices and flow resistance, particularly during exhalation, increasing iWOB. In contrast, the Inspire rPAP's narrower, multi-channel design effectively shielded the patient interface from high-energy flows, reducing interaction with expiratory streams. These findings highlight the critical role of internal flow-guiding geometry in pressure regulation and iWOB. The study underscores the value of CFD modeling in optimizing neonatal CPAP systems to improve respiratory support and reduce the burden on preterm infants.