What are SATs and SBTs?
SATs (Spontaneous Awakening Trials) and SBTs (Spontaneous Breathing Trials) are paired protocols used in mechanically ventilated ICU patients to assess readiness for liberation from sedation and mechanical ventilation, respectively. 1
Spontaneous Awakening Trials (SATs)
SATs involve temporarily stopping or reducing sedation to assess a patient's neurologic status and readiness to breathe without heavy sedation. 1
SAT Protocol Components:
- Daily safety screening must be performed on all patient-days where sedation/analgesia is being administered 1
- Sedation should be minimized but does not need to be completely stopped during the trial 2
- Protocols that pair daily sedation interruption with SBTs show superior outcomes compared to standard sedation management 2
- SAT safety screens are passed in approximately 49-82% of instances when performed 1
- When SAT safety screens are passed, the actual SAT should be performed in ≥95% of cases 1
Clinical Pitfall:
- The American College of Chest Physicians/American Thoracic Society guidelines suggest using protocols that minimize sedation for patients ventilated more than 24 hours, as excessive sedation delays weaning 2
Spontaneous Breathing Trials (SBTs)
SBTs are systematic assessments where ventilator support is reduced to minimal levels (pressure support <8 cm H₂O or T-piece) for 30 minutes to evaluate whether a patient can maintain adequate gas exchange without excessive respiratory effort before extubation. 3, 4
SBT Protocol Components:
Pre-SBT Assessment (Daily Readiness Screening):
- Clinical stability with resolution or improvement of the primary cause of respiratory failure 4
- Adequate oxygenation maintaining acceptable oxygen saturation on current support 4
- Hemodynamic stability with no active myocardial ischemia and no significant vasopressor requirements 4
- Assessment should be undertaken daily 3
SBT Method Selection:
- For standard-risk patients: Conduct initial SBT with modest inspiratory pressure augmentation (5-8 cm H₂O) rather than T-piece alone 4
- For high-risk patients (prolonged ventilation >14 days, chronic lung disease, myocardial dysfunction, neurologic impairment): Use CPAP without pressure support or T-piece for more accurate assessment 4
SBT Duration:
- Standard-risk patients: 30 minutes is sufficient, as most SBT failures occur within this timeframe 3, 4
- High-risk patients: 60-120 minutes is more appropriate 4
During SBT - Failure Criteria (Signs of Poor Tolerance):
- Respiratory distress: increased respiratory rate, accessory muscle use, paradoxical breathing 3
- Hemodynamic instability: tachycardia, hypertension, or hypotension 3
- Oxygen desaturation or deterioration in gas exchange 3
- Altered mental status or agitation 3
- Diaphoresis or subjective discomfort 3
Post-SBT Assessment Before Extubation:
- Upper airway patency using cuff leak test 3
- Bulbar function evaluation 3
- Sputum load assessment 3
- Cough effectiveness - patients with weak coughs are four times as likely to have unsuccessful extubations 5
- Absence of respiratory distress 3
The ABC Bundle: Pairing SATs and SBTs
Implementation of paired SATs and SBTs (the "B" element of the ABCDEF bundle) improves outcomes for mechanically ventilated patients compared to standard sedation management. 1
Performance Metrics:
- SBT safety screens should be performed in ≥96% of eligible patient-days 1
- When SBT safety screens are passed (56-66% of instances), the actual SBT should be performed in ≥93% of cases 1
- SBT success rates range from 53-75% depending on patient risk factors and trial method 1
Critical Clinical Pitfalls to Avoid
- A successful SBT does not guarantee successful extubation - approximately 10% of patients who pass an SBT will still fail extubation within 48 hours 3, 6
- Do not rely solely on respiratory parameters during the SBT; you must also assess upper airway patency, bulbar function, sputum load, and cough effectiveness before extubation 3
- Pressure-supported SBTs may underestimate post-extubation work of breathing, potentially leading to premature extubation 4
- Do not repeat a failed SBT on the same day - failed SBTs indicate respiratory muscle fatigue that needs time to resolve 4
- Patients with moderate-to-abundant secretions are more than eight times as likely to have unsuccessful extubations as those with no or mild secretions 5
- Poor cough strength and excessive secretions are synergistic in predicting extubation failure (risk ratio 31.9) 5
Extubation Success Definition
Extubation is considered successful if the patient does not require reintubation or noninvasive ventilation within 48 hours. 4, 6