When can a mechanically ventilated patient be weaned if they are hemodynamically stable (no or low‑dose vasopressor support, heart rate 60‑120 bpm, systolic blood pressure >90 mm Hg), have adequate oxygenation (fraction of inspired oxygen ≤0.40, positive end‑expiratory pressure ≤5 cm H₂O, PaO₂/FiO₂ ratio >150‑200 mm Hg), acceptable ventilation (PaCO₂ ≤50 mm Hg, pH ≥7.25), and are neurologically alert (awake, following commands, intact gag reflex) with an improving underlying cause?

When to Wean a Patient from Mechanical Ventilation

Patients meeting the described criteria—hemodynamically stable with minimal vasopressor support, adequate oxygenation (FiO₂ ≤0.40, PEEP ≤5 cm H₂O, PaO₂/FiO₂ >150–200), acceptable ventilation, neurologically alert, and improving underlying disease—should proceed immediately to a spontaneous breathing trial using pressure support ventilation (5–8 cm H₂O) rather than delaying weaning. 1, 2, 3

Daily Readiness Assessment

Before initiating any weaning attempt, verify that all of the following criteria are met:

• Resolution or significant improvement of the primary condition requiring mechanical ventilation 1, 2, 3
• Hemodynamic stability defined as no vasopressor support or only low-dose vasopressors, heart rate 60–120 bpm, systolic blood pressure >90 mm Hg 1, 2, 3
• Adequate oxygenation: FiO₂ <0.50, PEEP ≤5 cm H₂O, PaO₂/FiO₂ ratio ≥150–200 mm Hg 1, 2, 3
• Acceptable ventilation: PaCO₂ ≤50 mm Hg, pH ≥7.25 2, 3
• Neurologic readiness: Patient is arousable, follows simple commands (e.g., open eyes, squeeze hand), has adequate mental status, and intact airway reflexes including gag reflex 1, 2, 3
• No new potentially serious conditions and no planned procedures within the next 12–24 hours 2

Critical pitfall: Do not commence weaning when PaO₂ <55 mm Hg on FiO₂ ≥0.40, as the probability of weaning failure is markedly increased 2

Spontaneous Breathing Trial Technique

The American Thoracic Society and American College of Chest Physicians recommend conducting the initial SBT with modest inspiratory pressure support (5–8 cm H₂O) with PEEP 5 cm H₂O rather than T-piece alone. 1, 2, 3

Evidence Supporting Pressure Support Over T-Piece:

• SBT success rate: 84.6% with pressure support vs. 76.7% with T-piece (RR 1.11,95% CI 1.02–1.18) 1, 2
• Extubation success rate: 75.4% with pressure support vs. 68.9% with T-piece (RR 1.09,95% CI 1.02–1.18) 1, 2
• Trend toward lower ICU mortality: 8.6% vs. 11.6% with pressure support technique 2

SBT Duration:

• Standard-risk patients: 30 minutes, as most failures occur within this timeframe 1, 2, 3
• High-risk patients: 60–120 minutes for better predictive accuracy 2, 3

SBT Parameters:

• Maintain FiO₂ at 40% or lower during the trial 1, 2
• Set PEEP at ≤5 cm H₂O 1, 2

SBT Failure Criteria—Terminate Immediately If Any Develop:

• Respiratory distress: Respiratory rate >35 breaths/min or increasing trend, use of accessory muscles, abdominal paradox 1, 2
• Oxygen desaturation: SpO₂ <90% 1, 2
• Hemodynamic instability: Heart rate >140 bpm or sustained increase >20%, systolic blood pressure >180 mm Hg or <90 mm Hg 1, 2
• Altered mental status, agitation, increased anxiety, or diaphoresis 1, 2
• Deteriorating gas exchange 1

Critical pitfall: Do not repeat SBTs on the same day after failure—this leads to respiratory muscle fatigue and worsening outcomes 1

Rapid Shallow Breathing Index (RSBI)

The RSBI is the most validated predictor of weaning success with an area under the ROC curve of 0.89 2:

• RSBI ≤105 breaths/min/L: Acceptable to proceed with SBT 2
• RSBI <80 breaths/min/L: Increases likelihood of successful weaning by ~7.5-fold 2
• RSBI >100 breaths/min/L: Strong negative predictor (probability of success only 0.04) 2

Measurement technique: Measure after 30–60 minutes of spontaneous breathing using a handheld spirometer attached to the endotracheal tube while the patient breathes spontaneously for 1 minute 2

Pre-Extubation Assessment

Before extubation, assess the following:

• Upper airway patency: Perform a cuff-leak test, especially in patients with risk factors for laryngeal edema (female gender, nasal intubation, difficult/traumatic intubation, large endotracheal tube, high cuff pressures) 2
• Bulbar function and intact swallowing 1
• Cough effectiveness: Intact cough on suctioning with minimal secretions or effective clearance mechanism 1, 2
• Sputum load 1

A positive cuff-leak test markedly reduces the risk of post-extubation stridor, which accounts for approximately 15% of early reintubations 2

Identification of High-Risk Patients for Extubation Failure

Patients are considered high-risk when any of the following are present:

• Age >65 years with multiple comorbidities 1, 2
• Cardiac failure as the primary cause of respiratory failure 1, 2
• APACHE II score >12 on the day of extubation 2
• Failure of more than one prior SBT 1, 2
• PaCO₂ >45 mm Hg after extubation 2
• Presence of ≥1 comorbid condition (e.g., COPD, congestive heart failure) 1, 2
• Weak cough or excessive secretions 1, 2
• Prolonged mechanical ventilation (>14 days) 3

Post-Extubation Strategy

For High-Risk Patients:

The American Thoracic Society and Surviving Sepsis Campaign strongly recommend prophylactic noninvasive ventilation (NIV) applied within 1 hour after extubation for high-risk patients. 1, 2, 3

Benefits of prophylactic NIV in high-risk patients:

• Reduces reintubation risk (RR 0.61,95% CI 0.48–0.79) 1, 2
• Lowers mortality (RR 0.54,95% CI 0.41–0.70) 1, 2
• Shortens ICU length of stay by approximately 2.5 days 2
• In hypercapnic patients (PaCO₂ >45 mm Hg), further reduces 90-day mortality 2

NIV settings: Start with IPAP 10–12 cm H₂O and EPAP 5–10 cm H₂O, titrating FiO₂ to maintain SpO₂ 88–92% 2

Alternative for high-risk patients: High-flow nasal cannula (HFNC) lowers reintubation rates to 4% versus 21% with conventional oxygen (P = 0.01) 2

For Standard-Risk Patients:

• Extubate directly to supplemental oxygen via face mask or nasal cannula, targeting SpO₂ 88–92% 1, 2
• Monitor SpO₂, respiratory rate, and work of breathing continuously for the first 24 hours 2
• Do not delay extubation in patients <65 years who pass their first SBT, have normal PaCO₂, and lack significant respiratory or cardiac comorbidities 2

Protocol-Driven Weaning Implementation

The Society of Critical Care Medicine and Surviving Sepsis Campaign strongly recommend implementing a standardized weaning protocol with daily SBTs. 1, 2

Benefits of protocol-driven weaning:

• Reduces total mechanical ventilation duration by approximately 25 hours (or ~50% in some studies) 1, 2
• Shortens ICU length of stay by approximately 1 day 2
• Increases overall weaning success rates 2

Protocol execution: Should be carried out by respiratory therapists or nurses, with physician approval required only for the final extubation decision 2

Special Considerations for Sepsis Patients

The Surviving Sepsis Campaign issues a strong recommendation (high-quality evidence) to employ daily SBTs and structured weaning protocols for mechanically ventilated patients with sepsis who meet readiness criteria. 1, 2

• Maintain head of bed elevation between 30–45 degrees throughout the weaning process to limit aspiration risk and prevent ventilator-associated pneumonia 2

Sedation Management During Weaning

Light-target sedation that keeps patients awake, cooperative, and able to follow simple commands is associated with shorter duration of mechanical ventilation and reduced ICU length of stay 2

• Either daily sedation interruption or maintaining a light-target sedation level reduces ventilator time compared with deeper, continuous sedation strategies 2

Acceptable Extubation Failure Rate

An extubation failure rate of 5–10% is considered acceptable in contemporary practice 2. Approximately 10% of patients who successfully complete an SBT will still fail extubation; this rate is regarded as normal and does not imply inadequate assessment 2.

Definition of extubation success: Patient does not require reintubation or NIV within the first 48 hours post-extubation 2