Ventilation modes
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Supplementary features:
• Apnoea response
• Manual breath
Spontaneous breaths are permitted between mandatory breaths as shown in the figure above. In order
to promote synchrony with the patient's spontaneous efforts, mandatory breaths may be patient
triggered. Such patient triggering will cause some variation in the mandatory ventilation respiratory rate.
V-SIMV - Volume Synchronised Intermittent Mandatory Ventilation
V-SIMV is a mixed ventilation mode delivering volume-controlled mandatory breaths and
pressure-supported spontaneous breaths.
Mandatory breaths are delivered at a set frequency and spontaneous breaths are permitted between
mandatory breaths.
For mandatory breaths
The inspiratory volume is set using Vt and is initiated by either:
- the ventilator at a set respiratory rate
- the patient - if the patient effort is close enough to the next scheduled mandatory breath. This
time is 60% of the breath period or 10 seconds, whichever is less.
End of inspiration (switch from inspiration to expiration) is controlled by the ventilator (time-triggered
breath)
For spontaneous breaths
The inspiratory pressure support is set using PS. Inspiration is:
- initiated by the patient (spontaneous-triggered breath) and
- ended by the patient (spontaneous-cycled breath)
The patient is free to take any number of spontaneous breaths between mandatory breaths.
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