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Theory of Operations
the option of unrestricted spontaneous breathing even while pressure in the circuit is elevated to
the pressure limit level. This type of ventilation is referred to as Biphasic Pressure Release Ventilation
(BPRV)*. It is considered to be more comfortable for patients with an active respiratory drive who are
ventilated with Pressure Control. Open exhalation valve is turned on via the Advanced data set to
achieve BPRV breaths.
If a patient makes an expiratory effort, such as a cough, against a closed exhalation system (for
example, open exhalation valve off) during the inspiratory phase of a pressure-controlled
mandatory breath, airway pressure will rise above the target pressure. When open exhalation
valve is on, the ventilator actively controls the exhalation valve so that excess pressure is vented
out, the degree of pressure overshoot is minimized, and airway pressure is maintained close to
the target pressure.
Volume Target (Volume Target Pressure Control—VTPC)
A.2.4
Volume Targeted Pressure Control* is a hybrid Pressure Control breath type where the ventilator
attempts to achieve (target) a user-set tidal volume using the lowest Pressure Control level. These
are much like Pressure Control mandatory breaths except that the Pressure Control level is
managed breath-by-breath by the ventilator in steps of up to 3 cmH
in VTPC is limited to a level that is between 5 cmH
in order to try to achieve the targeted (user set) tidal volume within the (user set) inspiratory time.
The set tidal volume is not guaranteed for each breath; it is a target.
The first VTPC mandatory breath delivered after Volume Target is turned on is at a pressure control
level equal to PEEP/CPAP+5 cmH
Spontaneous breaths in VTPC/SIMV mode are Volume Target Pressure Support (VTPS) breaths.
Note:
If the Slope/Rise control is set too low, breathing circuit pressure may not reach the target pressure by the end
of inspiration.
Spontaneous Breath Management in SIMV and SPONT Modes
A.3
There are two forms of spontaneous breath assistance on the ventilator in SIMV and SPONT modes,
Pressure Support and Volume Target Pressure Support.
In Volume Control, Biphasic Pressure Release,* and Pressure Control SIMV, spontaneous breaths
with Pressure Support are available. In Volume Target Pressure Control SIMV, spontaneous breaths
are Volume Target Pressure Support breaths.
In SPONT, when Volume, BPRV, or Pressure Control mandatory breath type is selected, spontaneous
breaths with Pressure Support are available.
A-4
O/mbar above PEEP and the Pressure Limit setting
2
O/mbar.
2
* not available on the S model
O/mbar. The pressure change
2
* not available on the S model
Service Manual
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