In an adult mechanically ventilated patient with stable hemodynamics, adequate oxygenation (arterial oxygen tension ≥150 mm Hg on fraction of inspired oxygen ≤0.5, positive end‑expiratory pressure ≤5 cm H₂O), resolved cause of respiratory failure, alertness, and low sedation, how should a spontaneous breathing trial be performed and which clinical and ventilatory parameters should be monitored to determine success?

How to Perform a Spontaneous Breathing Trial

Conduct the initial spontaneous breathing trial using pressure support ventilation of 5–8 cm H₂O with PEEP 5 cm H₂O for 30 minutes in standard-risk patients, monitoring for signs of respiratory distress, hemodynamic instability, or oxygen desaturation. 1, 2

Pre-SBT Readiness Screening

Before initiating any SBT, confirm the patient meets all of the following criteria daily:

• Patient is arousable and able to follow simple commands (open eyes, maintain eye contact, squeeze hand) 2
• Hemodynamic stability without significant vasopressor requirements and no active myocardial ischemia 1, 2
• Adequate oxygenation: PaO₂ ≥150 mm Hg on FiO₂ ≤0.5 and PEEP ≤5 cm H₂O 3, 1
• Resolution or improvement of the primary cause of respiratory failure 1, 2
• Minimal sedation targeting a level where the patient can interact 2

SBT Technique and Duration

Standard-Risk Patients

• Use pressure support 5–8 cm H₂O with PEEP 5 cm H₂O rather than T-piece or CPAP alone 1, 2
• Duration: 30 minutes, as most SBT failures occur within this timeframe 1, 2
• This approach achieves 84.6% SBT success versus 76.7% with T-piece 1, 2

High-Risk Patients

• Extend SBT duration to 60–120 minutes for more accurate assessment 1, 2
• Consider using T-piece or CPAP without pressure support to better assess true extubation readiness 1, 2
• High-risk factors include: COPD or heart failure, prolonged ventilation >14 days, previous failed extubation, ineffective cough, impaired bulbar function, or age >65 with multiple comorbidities 1, 2, 4

Parameters to Monitor During SBT

Immediate Failure Criteria (Terminate SBT and Resume Ventilation)

Respiratory parameters:

• Oxygen saturation <90% 2
• Respiratory rate increase with accessory muscle use or paradoxical breathing 1
• Subjective dyspnea or increased work of breathing 1

Hemodynamic parameters:

• Heart rate >140 beats/min or sustained increase >20% from baseline 2
• Systolic blood pressure >180 mm Hg or <90 mm Hg 2

Neurologic parameters:

• Increased anxiety, agitation, or altered mental status 1, 2
• Diaphoresis 1, 2

Post-SBT Assessment Before Extubation

Passing the SBT alone is insufficient—approximately 10% of patients who pass still fail extubation within 48 hours. 1, 4 Therefore, assess the following additional factors:

Airway Competence

• Cough strength: Patients with weak cough (grade 0–2 on 0–5 scale) are 4 times more likely to fail extubation 5
• Secretion burden: Moderate-to-abundant secretions increase extubation failure risk 8.7-fold 5
• White card test: Ask patient to cough onto a card held 1–2 cm from the endotracheal tube; if secretions are propelled onto the card, this predicts successful extubation 5
• The combination of weak cough AND abundant secretions increases failure risk 32-fold 5

Upper Airway Patency

• Perform cuff leak test in patients at high risk for post-extubation stridor (intubated >7 days, traumatic intubation, prolonged high cuff pressures) 2
• If cuff leak test fails, administer systemic corticosteroids at least 4 hours before extubation 2

Bulbar Function

• Assess swallowing ability and gag reflex to ensure airway protection 1, 4

Post-Extubation Management

High-Risk Patients Who Pass SBT

Extubate directly to preventive noninvasive ventilation (NIV) applied immediately after tube removal rather than standard oxygen therapy 2, 4

This strategy reduces:

• Reintubation by 39% (RR 0.61,95% CI 0.48–0.79) 2
• Mortality by 46% (RR 0.54,95% CI 0.41–0.70) 2
• ICU length of stay 2

Standard-Risk Patients

Extubate to high-flow nasal oxygen (40–60 L/min) rather than conventional oxygen 2

Critical Pitfalls to Avoid

• Do not increase FiO₂ during the SBT, as this masks the patient's true oxygenation capability 6
• Do not rely solely on rapid shallow breathing index (RSBI) to determine SBT readiness; it is not necessary and adds no predictive value 6
• Do not use T-piece trials in patients with cardiovascular instability, as they impose excessive respiratory load and hemodynamic stress 1
• Do not delay extubation in high-risk patients who pass an SBT; apply preventive NIV immediately 2
• Do not repeat SBT on the same day after failure; identify and address reversible causes first, as repeated attempts lead to respiratory muscle fatigue 1
• Do not use gradual weaning modes (SIMV or progressive pressure support reduction) as the primary liberation strategy; daily SBTs are superior 2

Implementation Protocol

The Surviving Sepsis Campaign strongly recommends using a protocolized weaning approach that includes daily screening and standardized SBT protocols, which reduces mechanical ventilation duration by approximately 25 hours and ICU stay by 1 day 3, 2