Research ArticleOriginal Research

Patient-Ventilator Interaction During Noninvasive Ventilation in Simulated COPD

Onnen Moerer, Lars-Olav Harnisch, Peter Herrmann, Carsten Zippel and Michael Quintel
Respiratory Care January 2016, 61 (1) 15-22; DOI: https://doi.org/10.4187/respcare.04141

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Figures

  • Fig. 1.
    Fig. 1.

    Schematic display of one breathing cycle. Shown is an example display of a pressure-time curve (Pressure ASL [cm H2O]) and a flow-time curve (Flow Ventilator [L/min]) of a pressure-supported breath cycle in ventilation via face mask. The vertical dashed lines mark the beginning (A) and the end (C) of a simulated inspiration effort. The distance A to B represents the inspiratory trigger latency; the distance C to D represents the expiratory cycle latency. PTPEXP = expiratory pressure-time product.

  • Fig. 2.
    Fig. 2.

    Whisker plot of expiratory cycle latency (TLEXP) in all tested conditions. Displayed are the values for expiratory cycle latency together for both interfaces, both respiratory rates, and both pressure support values. In low cycling criteria, trigger latency shows large values picturing delayed off-cycling. Raising the cycling criteria reduces trigger latency. The best setting in our study was 50% peak flow, taking all tested conditions into account (see also Table 2). Overdoing it by raising cycling criteria further led to negative expiratory cycle latency values describing premature cycling, the higher the off-cycling the more negative values get.

  • Fig. 3.
    Fig. 3.

    Expiratory cycle latency (TLEXP) according to height of pressure support. Both interfaces and both respiratory rates are displayed together; each ventilation situation is displayed as one mark. It can be seen that trigger latency values vary much more using high pressure support. Separated high values in both plots are cycling criteria of 10 and 20%. This figure shows clearly that low cycling criteria led to large delays, raising cycling reduced delay markedly.

  • Fig. 4.
    Fig. 4.

    Whisker plot of expiratory pressure-time product: Direct comparison of expiratory pressure-time product (PTPEXP) in face mask versus helmet in all tested situations. A very low cycling of 10% shows a large additional expiratory pressure load. Raising cycling criteria slightly already shows a large effect; this effect of diminishing expiratory pressure load continues until 40% (helmet) or 50% (face mask), respectively, where the least additional pressure load can be seen. The lowest values correlate closely with expiratory cycle latency (see Fig. 2).

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