75
Adjustable parameters in PRVC-CMV mode are:
V-SIMV (Volume Controlled Synchronized Intermittent Mandatory Ventilation)
In this mode mandatory breaths are volume controlled and spontaneous breaths are pressure
supported. This mode is a combination of mandatory and spontaneous breaths.
The curve of pressure versus time in V-SIMV mode is shown in the below figure. Inspiration
and the exhalation phases of mandatory breath are shown by red and dark green and
inspiration and the exhalation phases in spontaneous breath are shown by light green and
yellow.
Figure 8-4- Pressure curve in V-SIMV mode
The exhalation consists of two windows:
The patient respiratory effort triggers an assisted breath within Spont window. The patient
also can trigger a mandatory breath within Expectation window.
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.
Excessive increasing in pressure or volume could terminate inhalation. In this situation set
tidal volume may not deliver to the patient and corresponding alarm be activated.
As the
pressure approaches the pressure alarm (active pressure), the exhalation valve opens and
Definition
Parameter
Percentage of delivered oxygen to the patient
2
O
Mandatory breaths per minute
Rate
Inspiratory time
i
T
Positive end expiratory pressure
PEEP
Target tidal volume delivered per breath
t
V
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
Time required for inspiratory pressure to rise to set pressure
Rise Time
