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 RR and V_T 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 RR and overall WOB (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 quick as possible based on patient status and tolerance of changes.

Minimal settings refers to minimal pressure support as well as minimal PEEP (PEEP of 5 cmH₂0 as discussed in previous chapters). Once minimal settings are reached, this is termed a Spontaneous Breathing Trial (SBT). SBTs remain the standard in most ICUs as one of the definitive tests to assess if the patient is ready for discontinuation of 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 5-7 cmH₂0). The patient’s RR, 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.