CYCLING-OFF GUIDED BY REAL-TIME WAVEFORMS ANALYSIS: PILOT STUDY ON NEXT-GENERATION PSV

Introduction: Analysis of waveforms, displayed on the ventilator screen, by experienced clinician has demonstrated to be a reliable tool to understand whether the ventilator is switching from inspiration to expiration at the right time; it allows adjustment of expiratory trigger sensitivity (ETS) in order to prevent asynchronies occurrence. However each modification of ventilator settings requires a new adjustment of ETS, which means that the continuous presence of the clinician at bedside would be necessary: a single ETS value is not fit for each respiratory act of the same patient. Aim: The objective is to test a new automated system for cycling off, based on real time- analysis of waveforms by IntelliSync+ software, present on G5 ventilators (Hamilton Medical, CH). This system allows adjustment of ETS breath by breath, according to the specific requirements from the patient in that moment. Patients and methods: IntelliSync+ was tested in 6 patients and its effectiveness was compared with the one of default setting (ETS= 25% of peak inspiratory flow) and of optimized setting, adjusted by an experienced clinician after visual waveform analysis. Two different levels of pressure support were evaluated: clinically set level (PS basal) and basal PS with a 50% increase (PS+50). ETS optimized at basal pressure support (ETS opti1) was selected as initial value at PS+50 and then if necessary re-optimized (ETS opti2). Inspiratory trigger sensitivity was set at 2 l/min throughout the study. Results: Basal pressure support and PS+50% values were 12 ± 2 and 18 ± 3 cmH2O. ETS opti1 and ETS opti2 values were 36 ± 8 (range 25-50) and 51 ± 13 % (range 35-70). Early cycling was not observed. Compared to default setting, ETS opti1 decreased cycling delay and unassisted efforts at PS basal, but these favorable effects were not maintained at PS+50. Further optimization (ETS opti2) decreased cycling and trigger delay but did not affect unassisted efforts. When IntelliSync+ was activated, cycling delay was shorter and values of trigger delay and unassisted efforts were at least as low as with optimized settings of ETS. Conclusions: Improvement of patient- ventilator interaction was seen with optimized ETS at basal level of pressure support, however worsening was observed when the support pressure was increased and a new optimization was necessary in order to improve the interaction. Automated system IntelliSync+ performed better than default trigger and at least as well as optimized setting, decreasing total asynchrony time of about 50% in respect to default setting. As a collateral effect, it improved not only cycling off but also triggering, in particular ineffective efforts.