A spontaneous breathing trial (SBT) is a test for patients on mechanical ventilation, before they can be extubated and liberated from mechanical ventilation, i.e. return to normal breathing. SBTs are daily tests performed on intubated patients to determine if they meet criteria for extubation. [1]
The SBT involves placing the patient on minimal ventilatory support for a set period, typically 30–120 minutes, and under close monitoring. There are two common methods: In a T-Piece Trial, the ventilator is completely removed, and the patient breathes through a T-piece connected to the endotracheal tube and supplied with humidified oxygen. Because no ventilatory support is provided, this provides a pure test of the patient’s ability to breathe independently, and is more challenging. More commonly, low-level pressure support ventilation can be used, providing some inspiratory pressure (typically 5-8 cmH₂O) with or without Positive End-Expiratory Pressure (PEEP) (usually ≤5 cmH₂O). Automatic tube compensation (ATC) or minimal PSV helps patients overcome the added resistance of the endotracheal tube. This method is easier than a T-piece trial and is commonly used in ICU settings. Patients are more likely to be successfully extubated after a PSV trial compared to a T-piece trial. [2]
Spontaneous breathing trials (SBT) are often combined with spontaneous awakening trials (SAT). [3] [4]
A spontaneous breathing trial includes assessment of several criteria, including respiratory parameters, oxygenation, hemodynamics, mental status, and presence of airway/cough reflexes:
Respiratory Parameters
Oxygenation Criteria
Hemodynamic Stability
Neurological and Secretions Criteria
The SBT is stopped early if the patient shows signs of intolerance, including: [5]
If a patient fails the SBT, they are placed back on ventilatory support, and the cause of failure is assessed (e.g., muscle weakness, excess secretions, cardiac dysfunction, etc.). SBTs are typically repeated daily. More performing SBTs more frequently than daily is not associated with increased likelihood of successful extubation. [6]
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