Abstract
OBJECTIVE: In a bench study, we sought to evaluate the influence of regulation of pressurization rate (PR) on the imposed work of breathing (W1) and inspiratory flow (V1) pattern during pressure support ventilation (PSV). METHODS: A commercially available mechanical ventilator (Bear 1000) was connected to an active lung simulator; the ventilator was set with PEEP at 10 cm H2O and pressure support at 10 cm H2O above PEEP. Three differ- ent PR levels (-5, 0, and +5, arbitrary units) were tested at 2 different lev- els of inspiratory ‘effort’ (mean V1 0.45 and 0.9 L · s−1). The time from the onset of inspiratory effort to inspiratory flow delivery (tv1) and its pressure-time product per minute (PTP1), the pressure-time product from the onset of V1 (PTP2), the duration of the below-PEEP phase of the respiratory circuit pres- sure (tp=0) and the area of the pressure-volume curve below PEEP (W1) were measured as well as peak inspiratory flow (PIF) and the time to reach it (tPIF). RESULTS: No statistically significant differences in tv1 and PTP1 were observed among different PRs. On the contrary, PTP2, tp=0, and W1 were significantly reduced by PR adjustment. This variation was more pronounced with the higher inspiratory drive. At the same time, PIF was increased and tPIF shortened. CONCLUSION: Adjustments in PR can reduce imposed work of breathing during assisted spontaneous breaths and may improve patient comfort. Its regulation should be individually tailored to inspiratory effort and flow in each patient. [Respir Care 1996;41(10):880-884]
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