10.1 PSV for Weaning Patients From Mechanical Ventilation

The transition to a spontaneous mode is the most important step that most patients need to complete prior to being weaned off the ventilator and extubated. Weaning remains the number one reason for PSV to be used in the clinical setting. As long as a patient is triggering breaths on their own, they could be trialed on spontaneous mode.

In PSV, the pressure support (PS) would be set at a level to achieve adequate tidal volumes for the patient’s ideal body weight and ensure a reasonable respiratory rate. We only set the amount of support that is needed for this. Set the minimum pressure support to maintain the [latex]RR[/latex] and [latex]V_T[/latex] within those parameters.

Once on PSV, the pressure support is decreased as tolerated until “minimal settings” are reached. A clinician will know it is tolerated by watching a patient’s [latex]RR[/latex] and overall [latex]\text{WOB}[/latex] (Remember the DiapHRaGM mnemonic?) and assessing their bloodwork after all decreases in support. Usually, decreases in support are done 1-2 times a day depending on patient status but should never be delayed if a patient can support their breathing with less support. The ultimate goal is decreasing support to “minimal settings” as quickly as possible based on patient status and tolerance of changes.

Minimal settings refer to minimal pressure support as well as minimal PEEP (PEEP of [latex]5\text{ cmH}_2\text{O}[/latex] as discussed in previous chapters). Once minimal settings are reached, this is termed a Spontaneous Breathing Trial (SBT).

SBTs continue to be the gold standard in most Intensive Care Units for assessing a patient’s readiness to be taken off mechanical ventilation. Protocol-driven weaning strategies, such as SBTs, have demonstrated superiority over weaning approaches based solely on clinical judgement. Their success largely stems from eliminating the guesswork in setting ventilator parameters and instead offering clinically tested steps to follow, ensuring a more systematic and reliable process for weaning patients from mechanical ventilation.

When performing an SBT, patients are decreased to the minimal settings (slight variations of pressure support amount can be seen when comparing hospital to hospital, but most are around [latex]5\text{ - }7\text{ cmH}_2\text{O}[/latex]). The patient’s [latex]RR[/latex], work of breathing (WOB), and vitals are monitored for the duration of the test. If these vitals remain within normal limits after approximately 30 minutes, an arterial blood gas (ABG) is usually taken as well to ensure they remain normal. If the ABG results are good, the patient is considered to pass the SBT and can be considered as a candidate for extubation if all other criteria are met and the physician gives the order.

“PSV for Weaning Patients From Mechanical Ventilation” from Basic Principles of Mechanical Ventilation by Melody Bishop, © Sault College is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.