How should a 30-minute Spontaneous Breathing Trial (SBT) using Continuous Positive Airway Pressure (CPAP) +5 or Pressure Support Ventilation (PSV) 0/5 be approached?

Approach to 30-Minute SBT Using CPAP +5 or PSV 0/5

A 30-minute SBT using either CPAP +5 or PSV 0/5 is an acceptable and evidence-based approach for assessing extubation readiness, with the understanding that CPAP +5 (or PSV 5-8 cm H₂O) is preferred over zero pressure support for standard-risk patients, while PSV 0/5 (equivalent to T-piece) may be reserved for high-risk patients requiring more stringent assessment. 1, 2

Duration and Timing

• 30 minutes is the standard and sufficient duration for most patients, as the majority of SBT failures occur within the first 30 minutes 1, 2
• For high-risk patients (prolonged ventilation >14 days, chronic lung disease, myocardial dysfunction, neuromuscular disease, or previous failed extubation), consider extending the trial to 60-120 minutes for more accurate assessment 2
• Daily assessment of readiness for weaning should be performed before initiating any SBT 1, 2

Choice Between CPAP +5 and PSV 0/5

CPAP +5 (or PSV 5-8 cm H₂O) - Preferred for Standard-Risk Patients

• The American College of Chest Physicians/American Thoracic Society guidelines recommend conducting initial SBTs with modest inspiratory pressure augmentation (5-8 cm H₂O) rather than T-piece or zero pressure support 2
• Pressure-supported SBTs result in higher success rates (84.6% vs 76.7% for T-piece) and higher extubation success (75.4% vs 68.9%) 2, 3
• A 30-minute PSV trial with 8 cm H₂O pressure support led to significantly higher rates of successful extubation (82.3% vs 74.0%) compared to 2-hour T-piece trials 3
• This approach may hasten extubation without increasing reintubation risk 4, 3

PSV 0/5 (Equivalent to T-Piece) - Consider for High-Risk Patients

• For patients at high risk of extubation failure, CPAP without pressure support augmentation (PSV 0/5) provides a more stringent assessment and may be more specific in identifying patients truly ready for extubation 2
• T-piece trials are more demanding and may better predict post-extubation work of breathing, though they may unnecessarily delay extubation in some patients 4
• Among high-risk patients (>65 years or chronic cardiac/respiratory disease), PSV trials did not result in significantly more ventilator-free days compared to T-piece trials 5

Monitoring During the SBT

Signs of Poor Tolerance (Failure Criteria)

• Respiratory distress: increased respiratory rate, accessory muscle use, paradoxical breathing 1, 2
• Hemodynamic instability: tachycardia, hypertension, or hypotension 2
• Gas exchange deterioration: oxygen desaturation or worsening arterial blood gases 1, 2
• Neurologic changes: altered mental status, agitation, or subjective discomfort 2
• Diaphoresis or other signs of excessive work of breathing 2

Critical Pre-Extubation Assessment

Passing an SBT does not guarantee successful extubation—approximately 10% of patients who pass will still fail extubation within 48 hours. 1, 2, 6 Therefore, assess these additional factors before extubation:

• Upper airway patency: risk of post-extubation stridor or edema 1, 2
• Bulbar function: ability to protect airway and swallow 1, 2
• Sputum load and cough effectiveness: ability to clear secretions 1, 2, 6
• Neurologic status: adequate consciousness and airway reflexes 2

Post-Extubation Management

• For high-risk patients who pass an SBT, strongly consider prophylactic noninvasive ventilation (NIV) immediately after extubation rather than standard oxygen therapy 2, 6
• Successful extubation is defined as absence of need for ventilatory support for 48 hours 1, 2
• Close monitoring for 6-24 hours post-extubation with continuous pulse oximetry and cardiac monitoring 6

Common Pitfalls to Avoid

• Do not rely solely on SBT success: The SBT assesses respiratory load-to-capacity balance but does not evaluate upper airway patency, bulbar function, or cough effectiveness 1, 6
• Avoid same-day repeat SBTs after failure: Failed SBTs indicate respiratory muscle fatigue requiring time to resolve; address underlying causes before reattempting 2
• Beware of pressure-supported SBT limitations: PSV may underestimate post-extubation work of breathing, potentially leading to premature extubation in borderline cases 2, 4
• Recognize that more frequent screening with PSV may paradoxically delay extubation: One trial found that protocolized frequent screening combined with pressure-supported SBTs increased time to successful extubation 7

Practical Algorithm

1. Assess daily readiness: Clinical stability, resolution of primary respiratory failure cause, adequate oxygenation (FiO₂ ≤70%, PEEP ≤12 cm H₂O) 1, 2
2. Choose SBT method: CPAP +5 or PSV 5-8 cm H₂O for standard-risk patients; PSV 0/5 for high-risk patients requiring stringent assessment 2
3. Conduct 30-minute trial: Monitor for signs of failure; extend to 60-120 minutes if high-risk 1, 2
4. If SBT passes, assess additional factors: Upper airway, bulbar function, cough, secretions 1, 2
5. Extubate with appropriate post-extubation support: Prophylactic NIV for high-risk patients 2, 6
6. If SBT fails, identify and address causes: Do not repeat same day; optimize patient condition before next attempt 2