80
When the operator adjusts the parameters of a respiratory mode, he/ she is faced with
limitations in setting the upper and lower limits of these parameters, which are due to the
adjustment of other respiratory parameters.
Note:
During inhalation, if the airway pressure for any reason (such as the patient's cough) exceeds
the value specified for it, the exhalation valve opens and prevents further increase in pressure.
The flow and pressure curve in PSV mode is shown in the below figure. As you can see when
the patient respiratory effort is detected, the ventilator delivers a pressure supported breath to
assist the patient spontaneous breath (in PEEP condition, PEEP+ Psupport).
Figure 8-6- Pressure and flow curve in PSV mode
Adjustable parameters in this mode are:
Definition
Parameter
Percentage of delivered oxygen to the patient
2
O
Positive end expiratory pressure
PEEP
Pressure more than PEEP that applies to spontaneous breaths.
support
P
The method of detecting the patient's respiratory effort (flow or pressure).
Trigger
Threshold of detecting patient respiratory effort based on flow or pressure
F Trig/ P Trig
Percentage of peak inspiratory flow in spontaneous breath necessary to
terminate
inhalation
and initiate exhalation.
% Esens
Time required for inspiratory pressure to rise to set pressure
Rise Time
APRV (Airway Pressure Release Ventilation)
APRV is a pressure-based ventilation mode that allows patients to breathe spontaneously at
two user-selected pressure levels (Phigh, Plow).
