Influence of Airway Resistance Model Selection on NIV Bench Testing

Abstract

Bench testing of non-invasive ventilators (NIV) relies on mechanical lung simulators that enable controlled and reproducible evaluation of ventilator performance. Although linear (R) and parabolic (R _p ) airway resistance models are established and widely used in such simulators, their impact under realistic NIV conditions has not yet been investigated. In this study, three NIV scenarios, representing low (R5/R _p 5), medium (R20/R _p 20), and high (R50/R _p 50) airway resistance, were assessed using numerical simulations and experimental measurements. Flow- and volume-based metrics were employed to compare the resulting respiratory patterns. Expiratory triggering behavior showed only small differences between resistance models in the low and medium resistance ranges, but measurable deviations occurred under high-resistance conditions. In contrast, substantial and systematic differences were observed in tidal volume and peak inspiratory and expiratory flows: parabolic resistances consistently produced higher volumes, higher peak flows, and more symmetric flow profiles. These findings demonstrate that linear and parabolic resistance models do not behave interchangeably under realistic NIV conditions. The authors propose that bench-testing protocols should explicitly specify the airway resistance model and consider its interaction with the applied breathing pattern to ensure accurate ventilator performance assessment and comparability across studies.