When is it appropriate to start weaning an adult mechanically ventilated patient without neurological impairment?

When to Start Weaning from Mechanical Ventilation

Begin daily assessment for weaning readiness as soon as the patient shows clinical improvement—specifically when oxygenation improves, hemodynamic stability is achieved without vasopressors, and the underlying cause of respiratory failure has resolved. 1

Daily Readiness Screening Criteria

Perform daily screening using all of the following criteria before attempting any weaning trial:

• Resolution or significant improvement of the primary condition requiring mechanical ventilation 1, 2
• Adequate oxygenation: PaO₂/FiO₂ ratio ≥200 with PEEP ≤5 cm H₂O and FiO₂ ≤0.40 1, 2
• Hemodynamic stability: No vasopressor infusions or minimal/stable doses 1, 2
• Patient arousability: Absence of heavy sedation, patient can follow commands 1, 2
• Respiratory mechanics: Rapid shallow breathing index (RSBI) ≤105 breaths/min/L 1, 2
• Airway protection: Intact cough on suctioning with minimal secretions or effective clearance mechanism 1, 2

Critical Threshold to Avoid

Do not commence weaning when PaO₂ <55 mmHg on FiO₂ ≥0.40, as the probability of weaning failure is markedly increased 2

The Spontaneous Breathing Trial (SBT)

Once all readiness criteria are met, proceed immediately to an SBT—do not delay:

SBT Configuration (Evidence-Based Approach)

Conduct the initial SBT using modest inspiratory pressure augmentation of 5-8 cm H₂O rather than T-piece alone, as this approach has significantly higher success rates (84.6% vs 76.7%) and higher extubation success (75.4% vs 68.9%) 3, 1, 2

SBT parameters:

• Pressure support: 5-8 cm H₂O 3, 1, 2
• PEEP: ≤5 cm H₂O 2
• FiO₂: ≤0.40 2

SBT Duration

• Standard-risk patients: 30 minutes 1, 2
• High-risk patients: 60-120 minutes (most failures occur within the first 30 minutes, but high-risk patients require longer observation) 1, 2

Immediate SBT Termination Criteria

Stop the SBT immediately if any of the following develop:

• Respiratory rate >35 breaths/min or increasing trend 1, 2
• SpO₂ <90% 1, 2
• Heart rate >140 bpm or sustained increase >20% 1, 2
• Systolic blood pressure >180 mmHg or <90 mmHg 1, 2
• Respiratory distress with accessory muscle use or abdominal paradox 1, 2
• Altered mental status, agitation, or increased anxiety 1, 2
• Diaphoresis or subjective discomfort 1, 2

Post-SBT Decision Making

If SBT is Successful

For standard-risk patients: Extubate directly to supplemental oxygen via face mask or nasal cannula, targeting SpO₂ 88-92% 2

For high-risk patients: Initiate prophylactic noninvasive ventilation (NIV) immediately after extubation, as this has shown decreased mortality (RR 0.54) and reduced weaning failure (RR 0.61) 1, 2

High-Risk Patient Identification

Consider a patient high-risk for extubation failure if any of the following are present:

• Age >65 years 2
• Cardiac failure as primary cause of respiratory failure 2
• APACHE II score >12 on day of extubation 2
• Failure of more than one prior SBT 2
• PaCO₂ >45 mmHg after extubation 2
• Presence of ≥1 comorbid condition (COPD, CHF) 2
• Weak cough or excessive secretions 2

If SBT Fails

Resume full ventilatory support and reassess readiness criteria daily 1. Avoid repeated same-day SBTs after failure, as this may lead to respiratory muscle fatigue 4

Protocol-Driven Approach: The Evidence

Use a standardized weaning protocol driven by respiratory therapists and ICU nurses rather than physician judgment alone, as this reduces total mechanical ventilation time by approximately 25 hours and shortens ICU length of stay by about 1 day 1, 2

The protocol should include:

• Daily readiness screening 1, 2
• Standardized SBT procedures 1
• Clear failure criteria 1
• Post-extubation monitoring plans 1

Common Pitfalls to Avoid

• Premature weaning: Do not attempt weaning in patients still requiring vasopressors or with unresolved primary pathology 2
• Delayed weaning: Clinicians tend to underestimate patients' capacity to breathe successfully when disconnected from the ventilator 3
• Over-reliance on predictive indices: Traditional weaning predictors (maximal inspiratory pressure, static compliance, RSBI alone) lack sufficient predictive value to be routinely useful without an actual SBT 3
• Ignoring cardiac dysfunction: Cardiac dysfunction is an increasingly recognized cause of weaning failure 5
• Successful SBT ≠ guaranteed extubation success: Approximately 10% of patients who pass an SBT will still fail extubation 2, 4

Post-Extubation Monitoring

Monitor continuously for the first 24 hours:

• SpO₂ targeting 88-92% 2
• Respiratory rate and work of breathing 2
• Signs of respiratory distress 2

Extubation success is defined as not requiring reintubation or NIV within 48 hours 3, 4