What are the readiness criteria and step‑by‑step protocol for weaning an adult patient from mechanical ventilation, including spontaneous breathing trial parameters, extubation criteria, and post‑extubation support?

Weaning from Mechanical Ventilation: Evidence-Based Protocol

Daily Readiness Screening Criteria

All mechanically ventilated patients should undergo daily assessment using the following mandatory criteria before attempting any spontaneous breathing trial: 1, 2, 3

• Resolution or significant improvement of the primary condition requiring mechanical ventilation 1, 2, 3
• Arousable and able to follow simple commands (e.g., open eyes, squeeze hand) 1, 2
• Hemodynamic stability without vasopressor support 1, 2
• Adequate oxygenation: PaO₂/FiO₂ ratio ≥ 200, FiO₂ ≤ 40-50%, PEEP ≤ 5 cm H₂O 1, 2, 3
• Rapid Shallow Breathing Index (RSBI) ≤ 105 breaths/min/L measured after 30-60 minutes of spontaneous breathing 1, 2
• Intact cough on suctioning with minimal secretions 1, 2
• No new potentially serious conditions or planned procedures in the next 12-24 hours 1, 2

Critical RSBI Thresholds

• RSBI < 80 breaths/min/L: 7.5-fold increased likelihood of successful weaning 1
• RSBI > 100 breaths/min/L: probability of success drops to 0.04 1
• Do not attempt weaning if PaO₂ < 55 mm Hg on FiO₂ ≥ 0.40 1

Spontaneous Breathing Trial Protocol

Standard-Risk Patients

Conduct the initial SBT using pressure support ventilation at 5-8 cm H₂O with PEEP 5 cm H₂O rather than T-piece alone, as this method increases SBT success from 76.7% to 84.6% and extubation success from 68.9% to 75.4% 1, 2, 3. This approach also shows a trend toward lower ICU mortality (8.6% vs 11.6%) 1.

SBT parameters for standard-risk patients: 1, 2, 3

• Pressure support: 5-8 cm H₂O
• PEEP: 5 cm H₂O
• FiO₂: ≤ 40%
• Duration: 30 minutes (most failures occur within this timeframe)

High-Risk Patients

Identify high-risk patients using these criteria: 1, 2, 3

• Age > 65 years with multiple comorbidities
• Cardiac failure as primary cause of respiratory failure
• APACHE II score > 12 on day of extubation
• Failure of more than one prior SBT
• Prolonged mechanical ventilation (> 14 days)
• Chronic lung disease (especially COPD)
• Weak cough or excessive secretions
• Impaired bulbar function or swallowing disorders

For high-risk patients, modify the SBT approach: 1, 2

• Use CPAP without pressure support (or T-piece) to more accurately assess true extubation readiness
• Extend SBT duration to 60-120 minutes for better predictive accuracy

SBT Failure Criteria—Terminate Immediately If:

1, 2, 3

• Respiratory rate > 35 breaths/min or increasing trend
• SpO₂ < 90%
• Heart rate > 140 bpm or sustained increase > 20%
• Systolic blood pressure > 180 mmHg or < 90 mmHg
• Increased anxiety or diaphoresis
• Use of accessory muscles or abdominal paradox
• Altered mental status or agitation

If SBT fails, do NOT repeat the trial on the same day—this leads to respiratory muscle fatigue and worsening respiratory mechanics 1. Resume pressure support ventilation, identify and address reversible causes, and attempt again the next day 1.

Pre-Extubation Assessment

Before extubation, assess the following beyond SBT success (remember: ~10% of patients who pass an SBT will still fail extubation): 1, 2

• Upper airway patency: Perform cuff-leak test in patients with risk factors (female gender, nasal intubation, difficult/traumatic intubation, large endotracheal tube, high cuff pressures) 1, 2
• Bulbar function: Ability to protect airway 1, 2
• Sputum load and cough effectiveness: Adequate secretion clearance 1, 2
• Absence of respiratory distress during the entire SBT 1

Extubation Strategy

Standard-Risk Patients

Extubate directly to supplemental oxygen via face mask or nasal cannula, targeting SpO₂ 88-92% 1, 2. High-flow nasal cannula (HFNC) is superior to conventional oxygen, reducing reintubation rates from 21% to 4% 2.

High-Risk Patients

Extubate directly to prophylactic noninvasive ventilation (NIV) within 1 hour after tube removal, which provides: 1, 2, 3

• Reduced reintubation risk (RR 0.61; 95% CI 0.48-0.79)
• Lower mortality (RR 0.54; 95% CI 0.41-0.70)
• Shorter ICU stay by approximately 2.5 days

Initial NIV settings for high-risk patients: 1

• IPAP: 10-12 cm H₂O
• EPAP: 5-10 cm H₂O
• FiO₂: titrate to SpO₂ 88-92%

For hypercapnic patients (PaCO₂ > 45 mm Hg during SBT), prophylactic NIV further reduces 90-day mortality (RR 0.58) 2.

Post-Extubation Monitoring

Monitor continuously for the first 24 hours: 1, 2

• SpO₂ (target 88-92%)
• Respiratory rate and work of breathing
• Signs of respiratory distress
• Hemodynamic stability

Extubation is considered successful if the patient does not require reintubation or NIV within 48 hours 1, 2. An acceptable extubation failure rate is 5-10%; higher rates suggest inadequate assessment 1, 2.

Protocol-Driven Implementation

Use a standardized weaning protocol led by respiratory therapists or nurses, with physician approval only for final extubation decision, which: 1, 2

• Reduces total mechanical ventilation duration by ~25 hours
• Shortens ICU length of stay by ~1 day
• Increases overall weaning success rates

Maintain light-target sedation that keeps patients awake, cooperative, and able to follow commands throughout the weaning process 2.

Critical Pitfalls to Avoid

• Never use SIMV for weaning—it is inferior to pressure support and T-piece methods 1, 2, 4
• Do not delay extubation in patients < 65 years who pass their first SBT, have normal PaCO₂, and lack significant comorbidities 2
• Pressure-supported SBTs may underestimate post-extubation work of breathing, potentially leading to premature extubation in borderline cases 1
• Do not rely solely on SBT success—screen for upper airway obstruction, ineffective cough, excessive secretions, swallowing disorders, and altered consciousness 1, 2
• Failed extubation requiring reintubation increases mortality by 10-20% and raises ventilator-associated pneumonia risk 1