Adjusting ventilator off-cycling in invasively ventilated COPD patients needs comprehensive adjustments

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Harnisch LO, Zippel C, Herrmann P, Quintel M, Moerer O.
Minerva Anestesiologica 2016 July;82(7):743-50

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 parame- ters that resulted from varying the iCC in a simulated COPD lung model.

A lung simulator was connected to an ICU ventilator through an endotra- cheal 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.

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 de- creased at iCC ≤ 40% but increased at iCC ≥ 50%. High RR/low PS constantly re- duced PTPEXP up to 60% iCC. Changes in iCC strongly influenced the resulting tidal volume.

Non-adapted ventilator iCC can cause patient-ventilator asynchrony. The success of assisted invasive ventilation and weaning relies on meticulous ad- justments.