7.3.2 Pressure-controlled ventilation modes
The device can compensate for a leakage of up to 50 l/min when pressure-controlled
ventilation modes are in use.
Pressure-controlled continuous mandatory ventilation (PC-CMV) 7.3.2.1
The ventilation pressure is the key factor for pressure-controlled
ventilation. It compares the preset nominal parameters such as inspiratory
peak pressure »Pinsp« and positive end expiratory pressure »PEEP« with
the pressure values measured during inspiration (Pinsp) and expiration
(PEEP). Any deviations caused, for example, by spontaneous breathing
activity are compensated quickly.
Under PC-CMV, the time required for mandatory insufflation is adjusted
in the »Tinsp« field. The set inspiratory peak pressure »Pinsp« is reached
during this time.
The magnitude of the tidal volume depends on the compliance of the
patient's lungs and results from the »PEEP« and »Pinsp« settings.
Spontaneous breathing attempts by the patient during inspiration are not
restricted by PC-CMV. The patient can breathe in and out freely at every
pressure level. The pressure is controlled, that is, it remains constant.
At the start of every inspiration phase, the flow increases rapidly to a
maximum value. At the end of inspiration, this flow decreases and
approaches zero. At this point in time, there is a balance of pressure
between the ventilator and the lungs. There is no further flow between the
Y piece and the lungs due to the pressure gradient.
The lungs have now been filled within the time indicated on the time
axis. The inspiratory pressure increase which can be set in the »Ramp
time« field determines how the ventilation pressure reaches its maximum
value within the inspiration time »Tinsp.«.
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