LAUSR

BACKGROUND: Faster inspiratory pressurization can improve patient–ventilator synchrony and reduce the patient's work of breathing during pressure controlled continuous mandatory (PC-CMV) ventilation. The characteristics of the pressurization ramp settings are not standardized across ventilators from different manufacturers. We performed a bench test of 5 models of ICU ventilators to examine the effects of pressurization ramp settings on the actual pressurization. METHODS: A twin-bellows lung model was used, in which one bellow simulates inspiratory muscle activity and the other simulates an adult normal lung model. We made the inspiratory effort by changing the tidal volume of the inspiratory muscle bellow. The effect of pressurization ramp settings on the performance of each ventilator was examined at 3 inspiratory effort levels (ie, none, ordinary, and strong). The pressurization ramp was set at 4 or 5 evenly divided steps from the minimum to maximum for each ventilator. The following parameters were measured: tidal volume, mean airway pressure, maximal inspiratory flow, time to maximal flow, and pressure–time products at 0.3 s (PTP0.3) and 0.5 s (PTP0.5) from the beginning of inspiration. PTP0.3 and PTP0.5 indicated levels of inspiratory pressurization. RESULTS: A proportional increase in PTP0.3 and PTP0.5 was observed with an increase in the pressurization ramp settings of the recent models of ventilators. PTP0.3 and PTP0.5 at ordinary and strong effort levels were similar in the recent models of ventilators. The actual adjustable ranges of PTP0.3 and PTP0.5 associated with change in the pressurization ramp settings differed between the 5 ventilators. CONCLUSIONS: The adjustable ranges of the pressurization were largely different among the different types of ventilators. The actual absolute inspiratory pressurization during PC-CMV varied between the different ventilators even at similar pressurization ramp settings. Users should be mindful of the differences in the pressurization ramp settings.