Increased air tube pressure during expiration (PEEP = positive end
expiratory pressure) improves alveolar ventilation/the pulmonary
exchange of gases.
For the patient to breathe in spontaneously, he first has to overcome the
resistance of the ETT before respiratory gas can flow into his lungs. The
respiratory gas flowing into the lungs causes the pressure at the ETT inlet
to decrease slightly. The faster the ventilator compensates for this drop in
pressure, the less effort the patient must make to breathe.
The ability of the ventilator to react to these fluctuations in pressure
resulting from the patient's spontaneous breathing depends on the inner
resistance. This ability is significant for the quality of the ventilator.
Depending on the selected ventilation mode (pressure or volume-
controlled ventilation), the inner resistance can also be used to
specifically react to a given ventilation scenario. The EVE
TR
makes a
basic distinction between pressure-controlled and volume-controlled
ventilation.
7.3.1 Volume-controlled ventilation
Never use volume-controlled ventilation modes with unattended patients.
Volume-controlled ventilation modes are only available for tidal volumes of 100 ml or
more.
Volume-controlled continuous mandatory ventilation (VC-CMV) 7.3.1.1
Volume-controlled continuous mandatory ventilation (VC-CMV)
"forces" the delivery of a preset inspiratory tidal volume. The ventilation
pressure delivered changes with the mechanical parameters of the lungs.
If compliance improves, the ventilation pressure needed to reach the
selected tidal volume adjust to the lowest possible value.
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