Performance Characteristics of Seven Bilevel Mechanical Ventilators in Pressure-Support Mode with Different Cycling Criteria: A Comparative Bench Study

Background: Pressure support ventilation from a bilevel device is a standard technique for non-invasive home ventilation. A bench study was designed to compare the performance and patient-ventilator synchronization of 7 bilevel ventilators, in the presence of system leaks.
Material and Methods: Ventilators were connected to a Hans Rudolph Series 1101 lung simulator (compliance, 50 mL/cmH2O; expiratory resistance, 20 cmH2O/L/s; respiratory rate, 15 breaths/min; inspiratory time, 1.0 s). All ventilators were set at 15 cmH2O pressure support and 5 cmH2O positive end-expiratory pressure. Tests were conducted at 2 system leaks (12–15 and 25–28 L/min). The performance characteristics and patient-ventilator asynchrony were assessed, including flow, airway pressure, time, and workload.
Results: The Breas Vivo30 could not synchronize with the simulator (frequent auto-triggering) at a leak of 25–28 L/min, but provided stable assisted ventilation when the leak was 12–15 L/min. Missed efforts and back-up ventilation occurred for the Weinmann VENTImotion and Airox Smartair Plus, requiring adjustment of trigger effort. All ventilators had a short trigger delay time (<200 ms), but significant differences between devices were found in triggering workload, pressurization appearance, tidal volume, and peak inspiratory flow. Premature cycling was frequent when the inspiratory termination criteria were at the highest sensitivity. Cycling synchronization was considerably improved by modifying expiratory triggering sensitivity settings, when available.
Conclusions: Performance and triggering workload varied significantly between bilevel ventilators, possibly due to software algorithm differences. Adjusting the cycling criteria settings can alter the shape of the inspiratory phase and peak expiratory flow, and improve patient-ventilator synchrony.

Keywords: Continuous Positive Airway Pressure, Algorithms, Air Pressure, Equipment Design, Oxygen - chemistry, Positive-Pressure Respiration - methods, Respiration, Respiration, Artificial - methods, Ventilators, Mechanical