minute ventilation. Breaths are pressure-control, and there is pressure support for
triggered breaths to achieve desired respiratory rate. As respiratory mechanics
change, the frequency–tidal volume pattern is automatically adjusted to maintain
this “optimal” pattern
4. Volume Support (AKA Automatic Pressure Ventilation)
Volume supoort is a pressure support mode that uses tidal volume as a feedback
control for continuously adjusting the pressure support level. Clinicians select a
target tidal volume, and ventilator makes automatic adjustments in inspiratory
pressure within a clinician-prescribed range. There is potential for automatic
support reduction by reducing PS as patient effort and mechanics improve.
- Inverse Ratio Ventilation
Inversing I:E ratio (I>E) is used to potentially improve oxygenation in a patient with
optimal PEEP and FiO2. It can be used with volume-limited or pressure-limited
mechanical ventilation.
- In pressure: increase I:E ratio
- In volume ramp wave: decrease peak inspiratory flow rate until I exceeds E
- In volume square wave: add and increase end-inspiratory pause until I exceeds E
- Neurally Adjusted Ventilatory Assists (NAVA)
NAVA is a new concept of mechanical ventilation. NAVA delivers assist to
spontaneous breathing based on, and proportional to the detection of the electrical
activity of the diaphragm. NAVA requires the insertion of a specialized naso-gastric
tube that detects the diaphragmatic electrical activity, and transmits it to the
ventilator. Theoretically this mode has the advantage of a much better patient-
ventilator synchrony.