Background: Patient-ventilator synchrony is essential for successful patient-triggered ventilation. This study compared the ability of a novel trigger algorithm, based on detailed analysis of flow changes (IntellSync+, Hamilton Medical), to trigger patient breaths with conventional algorithms. Methods: Three scenarios with different lung mechanics (normal, ARDS, and COPD) at three severities were simulated with a lung model (ASL 5000, IngMar Medical) ventilated with C6 (Hamilton Medical) in assist pressure control ventilation (PCV) or pressure support ventilation (PSV). In both modes, inspiratory pressure above PEEP was set at 15 cm H2O; PEEP was set at 5 cm H2O; and inspiratory trigger was selected from IntelliSync+ (IS+insp), flow trigger (1, 2, 3, 4, 5 L/min) or pressure trigger (-1, -2, -3, -4, -5 cm H2O). In PCV, the inspiratory time was set as the inspiratory time of the lung models. In PSV, expiratory trigger was set at IntelliSync+ (IS+exp) or the termination criteria (5%, 25%, and 40% for ARDS, normal, and COPD, respectively). The inspiratory trigger was sequentially changed in each model and five breaths per condition were collected to calculate trigger time and asynchronous events (auto-triggering and ineffective efforts IEs). In PSV, cycling delay time was compared between IS+exp and termination criteria. Similar measurements were performed in the presence of a leak (50% inspiratory tidal volume). Data for three consecutive normally triggered breaths were selected. Results: For the pressure trigger, none of the conditions resulted in three consecutive breaths successfully triggered. In normal (86 vs. 104 ms with leak, 79 vs. 101 ms without leak), ARDS (243 vs. 302 ms with leak), and COPD mechanics (312 vs. 330 ms with leak, 287 vs. 396 ms without leak), no difference were detected in trigger time between IS+insp and flow trigger, except ARDS without leak (244 vs. 325 ms, P < .05). In all scenarios, IEs occurred more frequently when using the flow trigger compared with the IS+insp (11% vs. 4% with leak, 7% vs. 2% without leak; P < .05 for both). IS+insp was the only algorithm with no IEs in PCV. In all scenarios, the cycling delay time with IS+exp was equal to or longer than that for the termination criteria (277 vs. 257 ms with leak, P = .62; 351 vs. 282 ms without leak, P < .005). Conclusions: IS+insp demonstrated similar trigger time and fewer IEs compared with flow trigger even in morbid lung conditions, whereas cycling delay was unaffected by IS+exp.
Morinishi et al. (Sun,) studied this question.