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Spontaneous Expiratory Threshold (Inspiration to Expiration):
A second method used to cycle to expiration during spontaneous breathing in all modes except T, CV, AC, and SIMV, is called Spontaneous Expiratory Threshold (SET). The SET rises in proportion to the inspiratory flow rate on each breath. When the SET and actual patient flow value are equal, the unit cycles to expiration.
IPAP
Pressure
EPAP
Spontaneous
Expiratory
Threshold
Flow
Spontaneous Expiratory
Threshold
Flow Reversal (Inspiration to Expiration):
As flow begins to decrease during inspiration, a flow reversal can occur due to a large leak around the mask or because the patient’s mouth is open. When the device senses this flow reversal, it automatically cycles to expiration.
Maximum IPAP Time (Inspiration to Expiration):
The maximum inspiratory time is determined by the adjustment of the Inspiratory time setting. A maximum IPAP time of 3.0 seconds acts as a safety mechanism to limit the time spent in inspiration during spontaneous breathing. For mandatory or assisted breaths, the maximum inspiratory time will equal the Inspiratory time setting up to 5.0 seconds.
Chapter 3 Modes, Features, and Alarms
