Pressure Support is a spontaneous mode of ventilation. The patient initiates the breath and the
ventilator delivers support with the preset pressure level. With support from the ventilator, the
patient also regulates the respiratory rate and the tidal volume. In Pressure Support, the patient
triggers all breaths, the preset inspiratory Pressure Support level is kept constant and there is a
decelerating flow. The peak pressure (Peak) is the sum of the settings for PEEP and Pressure
Support above PEEP.
Any change in the mechanical properties of the lung/thorax and/or patient effort will affect the
delivered tidal volume. If this occurs, the Pressure Support level must be adjusted to ensure the
desired ventilation.
Inspiration starts when the patient triggers a
breath and gas flows into the patient’s lungs at
a constant pressure. Since the pressure provided by the ventilator is constant, the flow will
decrease until the inspiratory cycle off is reached, when the expiration starts.
If no breath is detected within the interval determined by the apnea time setting, a apnea alarm will
be activated and the ventilator will go to backup ventilation to ensure breath delivery to the patient.
Expiration starts:
1.
when the inspiratory flow decreases to the preset inspiratory cycle off level [
Esens
].
2.
if the pressure increases 3 cmH2O above the Pressure Support level.
3.
if the upper pressure limit is exceeded.
4.
if the inspiration exceeds 2 s for adults and 1.5 s for infants.
The following figures show the Paw waveform and flow waveform in the PSV mode.
FIGURE 6-11
The paw and flow waveforms in PSV mode
6.5.4.2 Start PSV Mode
1. Push the [
Modes
] button to open the [
Modes
] menu.
2. Push [
PSV
] in the [
Modes
] menu, the [
controls
] menu for PSV mode is opened.
3. Adjust appropriately parameter settings for the patient and then confirm the settings to start
PSV mode.
6.5.4.3 Parameter Setup Area in PSV Mode