Abstract
Background:
Ventilators use similar measures and units to characterize how sensitive they are to patient effort. However, these devices use different sensor technologies and locations for detecting patient effort, which would suggest that these measures of sensitivity are not interchangeable. We sought to compare the trigger sensitivity of a few different ventilators by using an active lung simulator with different degrees of respiratory effort.
Methods:
WE used an ASL5000 servo-controlled lung model driven by RespiSim 4.0.2 software. A single lung model was used with base settings of resistance 20 cm H2O/L/s, compliance 15 mL/cm H2O, and respiratory rate of 16. Effort was controlled using the Pmus parameter, which can range from 0-30 cm H2O. Ventilators were configured to operate in pressure controlled CSV modes with PEEP 5 and pressure support of +10. The ventilators tested were the Draeger V500 (with and without proximal flow sensor), the Viasys LTV1150, and the Breas Vivo 65 (with single and dual limb circuits).
Results:
The V500 was the most sensitive ventilator, only requiring a Pmus of 1 when the trigger threshold was 0.5 L/min, irrespective of whether the proximal flow sensor was used. The LTV and Vivo were comparable and slightly less sensitive. We were unable to test the Vivo with the dual limb circuit at its highest sensitivity because of self-cycling issues using this model system. Self-cycling behavior was also noted with the LTV in pressure sensing mode and with the Vivo using a single limb circuit at low Pmus values.
Conclusions:
We were able to use an active lung simulator to compare the trigger sensitivities of different ventilators. Further study will be needed to understand how lung model parameters affect ventilator cycling in this model. Using this methodology with a non-servo-controlled lung model may also offer some insight. Testing other ventilators and circuits will provide helpful comparative data.
Trigger values are in lpm except for the Vivo, for which they are indexed values View all access options for this article.Ventilators and Pmus required for triggering
VENTILATOR and CONDITION
TRIGGER
Pmus
V500, proximal sensor
0.5
1.0
V500, proximal sensor
1.0
1.5
V500, expiratory sensor
0.5
1.0
V500, expiratory sensor
1.0
1.5
LTV1150
1.0
2.5
Vivo 65, single limb
1
1.5
Vivo 65, dual limb
2
2.5
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