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CPAP/PSV mode
M1204616
11 Specifications and theory of operation
Constant positive airway pressure/pressure support ventilation mode
mode is used on spontaneously breathing patients. This mode of
ventilation provides a constant support pressure once the ventilator
senses that the patient has made an inspiratory effort. In this mode,
the clinician sets the Pressure Support (Psupport) and PEEP levels.
The patient establishes the rate, inspiratory flow and inspiratory time.
The tidal volume is determined by the pressure, lung characteristics
and patient effort.
CPAP/PSV uses an inspiration termination level that establishes
when the ventilator will stop the pressure supported breath and cycle
to the expiratory phase. The inspiration termination level is user
adjustable from 5% to 75%. This parameter sets the percent of the
peak inspiratory flow that the ventilator uses to end the inspiratory
phase of the breath and to cycle into the expiratory phase. If the
inspiration termination is set to 30% then the ventilator will stop
inspiration when the flow decelerates to a level equal to 30% of the
measured peak inspiratory flow. The lower the setting the longer the
inspiratory time and conversely, the higher the setting the shorter the
inspiratory phase.
If the spontaneous inspiratory effort does occur within the delay
period, the ventilator delivers pressure controlled breaths with the
preset inspiratory pressure to bring the breath rate up to the minimum
rate. The delay period calculation is 60 s/minimum rate + ([60 s/
minimum rate] - seconds since start of last breath).
The inspiratory support pressure and the inspiratory pressure settings
are linked at the start of each case. When the inspiratory support
pressure setting is changed, the inspiratory pressure setting is
automatically adjusted to match the inspiratory pressure setting. The
link can be broken by changing the Pinsp setting through the Vent
Setup menu during the case.
Spontaneous breaths that occur during this mode are indicated by a
color change in the waveform.
CPAP/PSV settings:
•
Psupport
•
PEEP
•
Flow Trigger
•
End of Breath
•
Pmax
•
Pinsp
•
Minimum RR
•
Tinsp
•
Rise Rate
11-25
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