How to Conduct a Daily Spontaneous Breathing Trial
Perform a 30-minute spontaneous breathing trial using pressure support ventilation (5-8 cmH₂O) with PEEP ≤5 cmH₂O rather than T-piece alone, as this approach significantly increases successful extubation rates (82.3% vs 74.0%) and reduces mortality. 1, 2, 3
Patient Selection Criteria
Before initiating an SBT, verify that the patient meets ALL of the following readiness criteria:
- Arousable and adequate mental status 4, 2
- Hemodynamically stable without vasopressor agents 4, 2
- FiO₂ <0.50 (50%) 2
- PEEP ≤5 cmH₂O 4, 2
- No new potentially serious conditions 4, 2
- Resolution or improvement of the primary indication for mechanical ventilation 2
- Intact airway reflexes and ability to protect airway 2
SBT Protocol and Settings
Use pressure support ventilation of 5-8 cmH₂O with PEEP of 5 cmH₂O for the initial trial. 4, 2, 3 This approach is superior to T-piece alone, which may be overly stringent and unnecessarily delay extubation in patients who could successfully extubate. 3
The evidence strongly supports this method:
- SBT success rate: 84.6% with pressure support vs 76.7% with T-piece 2
- Extubation success rate: 75.4% with pressure support vs 68.9% with T-piece 2
- Significantly higher successful extubation at 72 hours (82.3% vs 74.0%, P=0.001) 1
Duration of the Trial
Conduct a 30-minute SBT for standard-risk patients. 2, 1 This shorter duration is sufficient for most patients and has been validated in large randomized trials. 1
For high-risk patients, extend the SBT to 60-120 minutes for more accurate prediction of extubation success. 2 High-risk features include:
- Prolonged mechanical ventilation (>14 days) 2
- Chronic lung disease 2
- Myocardial dysfunction 2
- Previously failed extubation 2
- Ineffective cough or impaired bulbar function 2
Monitoring and Termination Criteria
Terminate the SBT immediately if any of the following occur:
- Respiratory distress or increased work of breathing 2
- Hemodynamic instability 2
- Oxygen desaturation 2
- Altered mental status 2
- Diaphoresis 2
Timing and Frequency
Conduct SBTs daily, ideally completing assessment before noon each day. 5 Daily spontaneous breathing trials in appropriately selected patients reduce the duration of mechanical ventilation. 4
Coordinate the SBT with a spontaneous awakening trial to optimize outcomes. 4
Post-Extubation Management
For high-risk patients who pass the SBT, use prophylactic noninvasive ventilation (NIV) immediately after extubation rather than standard oxygen therapy. 2, 3 This is a strong recommendation with moderate-quality evidence. 3
For hypercapnic respiratory failure, particularly in COPD patients, NIV facilitates weaning with:
Common Pitfalls to Avoid
Do not routinely calculate the rapid shallow breathing index to determine SBT readiness, as it is not necessary. 5
Do not increase FiO₂ during the SBT, as this defeats the purpose of assessing the patient's ability to breathe with minimal support. 5
Do not use T-piece alone as the initial SBT method unless there are specific contraindications to pressure support, as it may unnecessarily delay extubation. 3, 1
Do not skip the daily screening process even if the patient failed an SBT the previous day, as clinical status can change rapidly. 4