Effects of assist parameter on the performance of proportional assist ventilation in a lung model of chronic obstructive pulmonary disease

Abstract

BackgroundHow the assist parameters affect synchronization and inspiratory workload in proportional assist ventilation (PAV) remains unknown. PurposeThis bench study aimed to optimize the PAV parameters by evaluating their effects on patient-ventilator synchrony and work of breathing (WOB) in a chronic obstructive pulmonary disease (COPD) model during noninvasive ventilation, compared with the pressure support ventilation (PSV) mode. MethodsThe Respironics V60 ventilator was connected to an ASL5000 lung simulator, which simulates lung mechanics in COPD (compliance, 50mL/cmH2O; expiratory resistance, 20 cmH2O/L/s; respiratory rate, 15 breaths/min; inspiratory time, 1.6 s). PAV was applied with different assistance levels, including flow assist (FA, 40–90% respiratory resistance) and volume assist (VA, 50–90% elastance). PSV was assessed using the same model. Measurements were obtained at a leak flow rate of 25–28 L/min. Performance characteristics, simulator-ventilator synchrony, and WOB were assessed. ResultsRunaway was prone to occur, and severe premature cycling was observed with VA75+FA level>65%. Compared with PSV, lower tidal volume (≤400mL) was observed during PAV with VA75+FA40-50 and FA50+VA40-80; similar and improved cycling synchrony was observed for FA50+VA80 and FA50+VA90 (cycling delay: −117.60±6.13 and −61.50±8.03 vs. −101.20±7.32ms). The reduced triggering workload was observed for VA75+FA60-65 and FA50+VA80-90. Total and patient WOB was improved with all tested assist level combinations, except for FA50+VA90. ConclusionsPAV reduces WOB but can induce asynchrony if improper settings are set, but the most optimal settings still need more clinical observations.