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Online ISSN 1827-1596
Lars O. HARNISCH, Carsten ZIPPEL, Peter HERRMANN, Michael QUINTEL, Onnen MOERER
Department of Anesthesiology, University of Goettingen Medical School, Goettingen, Germany
BACKGROUND: Patient-ventilator asynchrony that prolongs weaning and increases morbidity and mortality is common during invasive ventilation of patients with chronic obstructive pulmonary disease (COPD). In this context, the inspiratory cycling criteria (iCC) of the ventilator during assisted pressure support (PS) ventilation is a poorly acknowledged key factor. We investigated the changes of flow and pressure parameters that resulted from varying the iCC in a simulated COPD lung model.
METHODS: A lung simulator was connected to an ICU ventilator through an endotracheal tube. We studied iCC settings from 10% to 70% at different respiratory rates (RR) (15 and 30 bpm) and pressure support (PS) (5 and 15 cmH2O) settings and registered asynchrony-index, double-triggering, expiratory trigger latency (TLEXP), intrinsic PEEP (PEEPi), expiratory pressure time product (PTPEXP) and tidal volume.
RESULTS: At iCC≤20%, asynchrony occurred in 50% of all recordings in high RR/high PS. At a low RR, double triggering occurred at high iCC settings. It appeared at 50% iCC with low PS and at 60% iCC with high PS. TLEXP was positive at iCC 10% to 30% but decreased with increasing iCC (P<0.001). At low RR/high PS settings, PEEPi decreased at iCC≤40% but increased at iCC≥50%. High RR/low PS constantly reduced PTPEXP up to 60% iCC. Changes in iCC strongly influenced the resulting tidal volume.
CONCLUSIONS: Non-adapted ventilator iCC can cause patient-ventilator asynchrony. The success of assisted invasive ventilation and weaning relies on meticulous adjustments.