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30 Ventilation modes
PSV MODE
Pressure supported ventilation is intended to support spontaneous breath-
ing and to initiate machine ventilation whenever spontaneous respiration
fails. The support pressure (IPAP) and expiration pressure (PEEP) de
fi ne
the pressure range in which the patient is ventilated. The trigger thresh-
olds of the inspiration trigger and the expiration trigger can be adjusted
to the patient’s requirements. The adjustable frequency is a background
frequency. As long as this frequency is reached or exceeded through the
patient’s spontaneous respiration, the device reacts to every spontane-
ous inspiration with supportive pressure and follows the patient’s breath-
ing. If the background frequency is not reached, the device takes over the
mechanical ventilation until spontaneous respiration is registered again. To
allow pauses between the spontaneous respiratory efforts of the patient,
a delay of the time of the start of mechanical respiration is possible, by
setting an apnea time. The increase in pressure between PEEP and IPAP
can be selected by setting a ramp, which prescribes the form of the
fl ow
curve. The tidal volume adjusts itself to the condition of the lungs (com-
pliance and resistance). To safeguard a minimum volume, a value can be
preset, with the option of using additional pressure (IPAP + additional pres-
sure) to reach this minimum volume.
Time
Speci
fi
ed
pr
essur
e
IPAP
PEEP
Supported
Inspiration and
Expiration
Supported
Inspiration and
Expiration
Supported
Inspiration and
Expiration
Supported
Inspiration and
Expiration
Spontaneous
respiration triggger
Spontaneous
respiration triggger
In the PSV mode, the maximum and minimum volumes, as well as a maxi-
mum frequency, can be set as alarm parameters.
Fig. 5: PSV mode diagram