For getting an optimal synchronization between patient’s breathing cycle and the pressure cycle delivered by the ventilator, there are two triggerings,
i) one that induces the pressure rise from the low pressure Pl to the high pressure Ph
and ii) one that provokes the pressure release from Ph to Pl.
When the two cycles are phase synchronized, pressure rise is triggered at the beginning of the inspiratory effort, that is, at the beginning of the decrease of the ventilatory muscular pressure Pmus, and pressure release is triggered at the beginning of the pressure release associated with the beginning of the relaxation of the muscular pressure. Consequently, most of asynchrony events can be described using two parameters as follows (Fig. 1).
Depending on the value of these two parameters we may have :
We here proposed our own terminology for two main reasons. First, a ventilator is not breathing, so it cannot trigger inspiration. Second, the term "cycling" has no intuitive meaning and does not reflect the symmetry existing between pressure rise and pressure release. Moreover, there are two triggers in the functionning of the devices. We therefore believe that our terminology is closer to what actually occurs in patient-ventilator interactions. There are also other types of asynchrony events as
In order to describe the various situations we encounter in actual situations, we introduced a color map (Fig. 2) as follows .
Cycles can then be (more or less objectively) ranked from the best (purple) to the worst (red) quality using the color map as shown in Fig. 2.
 E. Fresnel, J.-F. Muir & C. Letellier, Realistic human muscle pressure for driving a mechanical lung, EPJ Nonlinear Biomedical Physics, 2, 7, 2014. Online