Performance of current intensive care unit ventilators during pressure and volume ventilation

Abstract

Background: Intensive-care mechanical ventilators regularly enter the market, but the gasdelivery capabilities of many have never been assessed. Methods: We evaluated 6 intensive-care ventilators in the pressure support (PS), pressure assist/control (PA/C), and volume assist/control (VA/C) modes, with lung-model mechanics combinations of compliance and resistance of 60 mL/cm H2O and 10 cm H2O/L/s, 60 mL/cm H2O and 5 cm H2O/L/s, and 30 mL/cm H2O and 10 cm H2O/L/s, and inspiratory muscle effort of 5 and 10 cm H2O. PS and PA/C were set to 15 cm H2O, and PEEP to 5 and 15 cm H2O in all modes. During VA/C, tidal volume was set at 500 mL and inspiratory time was set at 0.8 second. Rise time and termination criteria were set at the manufacturers' defaults, and to an optimal level during PS and PA/C. Results: There were marked differences in ventilator performance in all 3 modes. VA/C had the greatest difficulty meeting lung model demand and the greatest variability across all tested scenarios and ventilators. From high to low inspiratory muscle effort, pressure-to-trigger, time for pressure to return to baseline, and triggering pressuretime product decreased in all modes. With increasing resistance and decreasing compliance, tidal volume, pressure-to-trigger, time-to-trigger, time for pressure to return to baseline, time to 90% of peak pressure, and pressure-time product decreased. There were large differences between the default and optimal settings for all the variables in PS and PA/C. Performance was not affected by PEEP. CONCLUSIONS: Most of the tested ventilators performed at an acceptable level during the majority of evaluations, but some ventilators performed inadequately during specific settings. Bedside clinical evaluation is needed. © 2011 Daedalus Enterprises.