Pinsp setting in NIV-ST
My patient is being ventilated in NIV-ST mode and the clinician has ordered PEEP of 5 cmH2O and pressure support of 5 cmH2O. On my Hamilton Medical ventilator the control for adjusting pressure support in NIV-ST is labelled Pinsp (for HAMILTON-G5/S1: Psupport). So what value do I need to set?
In the literature and amongst the different ventilator manufacturers, the labelling for certain parameters or values may vary. On some ventilators, Pinsp refers to the total inspiratory pressure and equals PEEP plus the pressure support (Psupport), which is the additional (set) pressure applied for spontaneous breaths during the inspiratory phase.
However, on Hamilton Medical ventilators, the parameter Pinsp in NIV-ST is the same as Psupport in NIV. Pinsp thus refers to the applied delta pressure and not the total inspiratory pressure including PEEP. For the patient described above you would therefore set Pinsp at 5 cmH2O.
There are three different labels for this delta pressure, which depend on the mode and breath type (and thus the different function). For mandatory breaths, it is called Pcontrol and for spontaneous breaths, it is called Psupport. In modes where the breath type may alternate (e.g., PSIMV+), the same parameter is referred to as Pinsp. However in all instances, we are talking about the amount of pressure set by the user to be applied above PEEP. This ensures that Hamilton Medical ventilators deliver reliable driving pressures across all modes. Evidence has shown that driving pressure is the one parameter most relevant for lung-protective ventilation and strongly associated with hospital survival.
On Hamilton Medical ventilators it is only possible to set a “total” pressure in DuoPAP and APRV. This is because these modes operate based on two different CPAP levels and it is therefore necessary to set a maximum CPAP pressure including PEEP/Plow. In DuoPAP, you have the additional option of setting a level of Psupport to be applied above PEEP.
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