Responses of Bilevel Ventilators to Unintentional Leak: A Bench Study

Abstract

Background: The impact of leaks has mainly been assessed in bench models using continuous leak patterns which did not reflect real-life leakage. We aimed to assess the impact of the pattern and intensity of unintentional leakage (UL) using several respiratory models. Methods: An active artificial lung (ASL 5000) was connected to three bilevel-ventilators set in pressure mode; the experiments were carried out with three lung mechanics (COPD, OHS and NMD) with and without upper airway obstruction. Triggering delay, work of breathing, pressure rise time, inspiratory pressure, tidal volume, cycling delay and the asynchrony index were measured at 0, 6, 24 and 36 L/min of UL. We generated continuous and inspiratory UL. Results: Compared to 0 L/min of UL, triggering delays were significantly higher with 36 L/min of UL (+27 ms) and pressure rise times were longer (+71 ms). Cycling delays increased from −4 [−250–169] ms to 150 [−173–207] ms at, respectively 0 L/min and 36 L/min of UL and work of breathing increased from 0.15 [0.12–0.29] J/L to 0.19 [0.16–0.36] J/L. Inspiratory leakage pattern significantly increased triggering delays (+35 ms) and cycling delays (+263 ms) but decreased delivered pressure (−0.94 cmH2O) compared to continuous leakage pattern. Simulated upper airway obstruction significantly increased triggering delay (+199 ms), cycling delays (+371 ms), and decreased tidal volume (−407 mL) and pressure rise times (−56 ms). Conclusions: The pattern of leakage impacted more the device performances than the magnitude of the leakage per se. Flow limitation negatively reduced all ventilator performances.

Volume assured pressure support mode use for non‐invasive ventilation in pediatrics

“…32 The total leak is a sum of the intentional leak (flow through the leak ports in the mask interface to release exhaled carbon dioxide) and unintentional leak (unwanted leak in the system such as poor mask seal, open mouth with a nasal mask or damaged circuit/tubing). 32 Unintentional leaks can affect the efficacy of NIV therapy and result in poor tolerance, hypoventilation, sleep disturbance and patient-ventilator asynchrony 11,33 The algorithms for VAPS mode from ResMed (iVAPS) and Phillips (AVAPS) are dependent on a reasonable leak to ensure reliable performance and accurate data download. 34 A bench study completed by Fauroux et al 35 in inadequate ventilation, oxygen desaturations, sleep disturbances and exposure to higher inspiratory pressure/pressure support than required.…”

“…35,36 This can also lead to gastric distention, abdominal discomfort, vomiting and aspiration. 11 Lebret et al 33 demonstrated that in pressure support ventilation with a single limb circuit, the leak pattern affected device performance more than the magnitude of the unintentional leak. A dynamic inspiratory leak resulted in a significant increase in patient ventilator asynchrony with delayed trigger/cycle response, increased work of breathing and decrease in delivered pressure compared to continuous leak of up to 24 LPM.…”