Pressure Support Ventilation (PSV)
- Pressure Controlled
- Flow-Triggered – and the pressure support breaths are flow-triggered
Volume-limited… but it doesn't have to be
….Flow-limited (but doesn’t have to be flow-limited)
You have some degree of control over the tidal volume: you can adjust the pressure support value (the higher it is, the higher a tidal volume the patient will inhale). You can also decrease the flow cycling trigger (so the breath lasts longer)
The flow has to be fast to reach the present pressure rapidly (just as in PCV). Thereafter, as the pressure is reached, the flow rate has to drop swiftly, or else the pressure will continue to rise.
As soon as the flow drops to a set cycling target (usually, 25% of the flow limit), the ventilator cycles to expiration.
This mode is typically combined with SIMV, as the non-mandatory component.