PHILIPS Respironics Trilogy 202, User Manual, Page: 46 / 179

Chapter 3 Modes, Features, and Alarms
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B. Patient Flow
The total circuit flow is comprised of the circuit leak and the patient
flow. The calculated patient flow is the total flow minus the circuit
leak. Patient flow is a primary input into the triggering and cycling
mechanisms.
Auto-Trak Sensitivity
An essential feature of the device while operating in all modes is
its ability to effectively sense spontaneous breathing efforts, which
causes the ventilator to trigger to inspiration and cycle to expiration.
Because no preset sensitivity threshold can assure patient and
machine synchrony with changing breathing efforts and circuit
leaks, the device continuously tracks patient breathing patterns
and automatically adjusts sensitivity thresholds to ensure optimum
sensitivity as breathing patterns change or as circuit leaks change.
The algorithms used to ensure optimum sensitivity are the Volume
Trigger, Shape Signal, Spontaneous Expiratory Threshold (SET), Flow
Reversal, Maximum IPAP Time, and Volume Control Cycle.
Volume Trigger (Expiration to Inspiration):
The volume trigger is one method used to trigger inspiration during
spontaneous breathing in all modes except T and CV. The volume
trigger threshold is 6 ml of accumulated patient inspiratory volume.
When patient effort generates inspiratory flow causing 6 ml of
volume, inspiration is triggered.