PHILIPS Respironics Trilogy 202 User Manual page 47

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Shape Trigger/Shape Cycle (Expiration to Inspiration) (Inspiration to
Expiration):
The shape trigger/cycle is another method used to trigger inspiration
and/or cycle from inspiration to expiration during spontaneous
breathing in all modes except T and CV. This method continuously
tracks patient inspiratory and expiratory flow and adjusts the
spontaneous trigger and cycle thresholds for optimum sensitivity.
The Shape Signal appears as a shadow image of the patient's actual
flow. The shape signal functions as a sensitivity threshold at either
inspiration or expiration. When the patient's flow rate crosses the
shape signal the unit changes pressure levels. The following figure
illustrates how the shape signal is super-imposed onto the actual
waveform to trigger and cycle off IPAP. The shape signal is created
by offsetting the signal from the actual patient flow by 15 l/min and
delaying it for a 300 msec period. This intentional delay causes the
shape signal to be slightly behind the patient's flow rate.
A sudden change in patient flow will cross the shape signal, causing
the pressure level to change.
IPAP
Pressure
EPAP
Shape
Signal
Estimated
Flow
Patient
Flow
Trilogy 202 user manual
Cycle to
EPAP
Crossover
Point
Trigger to
IPAP
Crossover
Point
Shape Signal