Early trigger on ASV and how to fix it without changing the mode
How we can decrease the set RR in ASV and the consequences of doing so
As you can see in the settings on the right of the screen, there is no RR knob in ASV. To decrease the RR we must decrease the minute volume. However, since ASV uses a set of equations (Mead and Otis equations) to arrive at a tidal volume/rate combination for each minute volume, the target tidal volume will also decrease. Because this mode delivers pressure-limited breaths where inspiratory pressures are titrated to the target tidal volume, Pinsp and, consequently, the amount of support will decrease.
This is a good example of the loss of flexibility that is a consequence of the type of automation used in ASV. In order to drop the RR you must decrease the amount of support you will give the patient, which was not something we wanted to do.
This image shows how we treated the dyssynchrony by reducing the target minute volume from 125 to 80%. Note how Pinsp, marked in red, decreased from 7 in the prior pic to 5 cmH2O here, an unwanted consequence.
