What are the criteria and protocol for weaning a patient on mechanical ventilation (MV)?

Weaning Screen and Protocol for Mechanical Ventilation

Perform daily readiness screening using standardized criteria, and if met, conduct a spontaneous breathing trial (SBT) with 5-8 cm H₂O pressure support rather than T-piece, as this approach achieves significantly higher success rates (84.6% vs 76.7%). 1, 2

Daily Readiness Screening Criteria

Before attempting any SBT, verify ALL of the following criteria are met:

• Resolution of primary respiratory condition that necessitated intubation 2, 3
• PaO₂/FiO₂ ratio ≥200 with FiO₂ ≤40% 2, 4
• PEEP ≤5 cm H₂O 2, 3
• Hemodynamic stability without vasopressor infusions 2, 4
• Minimal secretions or effective clearance mechanism with intact cough on suctioning 2, 4
• Rapid shallow breathing index (RSBI) ≤105 breaths/min/L 2, 3
• Absence of heavy sedation or continuous sedative infusions 2
• Glasgow Coma Scale adequate for airway protection 5

Conducting the Spontaneous Breathing Trial

Use pressure support ventilation (PSV) of 5-8 cm H₂O for the initial SBT rather than T-piece, as this method produces higher extubation success rates (75.4% vs 68.9%) and is recommended by the American College of Chest Physicians/American Thoracic Society. 1, 2, 3

SBT Parameters:

• PEEP: ≤5 cm H₂O 2
• FiO₂: ≤40% 2
• Duration: 30 minutes for standard-risk patients; 60-120 minutes for high-risk patients (those with chronic respiratory disease, heart failure, or previous extubation failure) 2, 3

Immediate SBT Termination Criteria:

Stop the trial immediately if ANY of the following develop:

• Respiratory rate >35 breaths/min or increasing trend 2
• SpO₂ <90% 2
• Heart rate >140 bpm or sustained increase >20% from baseline 2
• Systolic blood pressure >180 mmHg or <90 mmHg 2
• Use of accessory muscles or abdominal paradox 2
• Increased anxiety or diaphoresis 2
• Altered mental status or agitation 3

Post-SBT Decision Making

If SBT Successful (No Termination Criteria):

Assess additional extubation readiness factors before removing the endotracheal tube:

• Cough effectiveness - critical for airway protection 4
• Bulbar function and ability to protect airway 4
• Sputum load and secretion clearance ability 4
• Upper airway patency (consider cuff-leak test if concern for edema) 4

Extubation Strategy Based on Risk:

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

High-risk patients (chronic respiratory disease, heart failure, hypercapnia, obesity, age >65, multiple comorbidities): Extubate directly to prophylactic noninvasive ventilation (NIV) starting with IPAP 10-12 cm H₂O and EPAP 5-10 cm H₂O, as this reduces mortality (RR 0.54) and weaning failure (RR 0.61) 2, 4, 3

Alternative for high-risk patients: High-flow nasal cannula oxygen therapy has shown reduced reintubation rates 1, 4

Post-Extubation Monitoring

Monitor continuously for the first 24 hours and assess for 48 hours total, as extubation is only considered successful if no reintubation or NIV is required within 48 hours. 2, 4

Monitor for:

• SpO₂ targeting 88-92% (avoid excessive oxygen in chronic hypercapnia) 2
• Respiratory rate and work of breathing 2
• Signs of respiratory distress 4
• Hemodynamic stability 3

If SBT Fails

Resume full ventilatory support immediately and investigate correctable causes:

• Respiratory muscle fatigue 3
• Excessive secretions requiring physiotherapy 1, 4
• Cardiac dysfunction or fluid overload 3
• Patient-ventilator dyssynchrony 3
• Inadequate resolution of primary disease 4

Do not attempt repeated same-day SBTs as this causes respiratory muscle fatigue. 4

Consider tracheostomy if patient fails multiple extubation attempts or requires >7 days of weaning after first SBT (prolonged weaning category). 4, 3

Critical Pitfalls to Avoid

• Do not rely solely on RSBI or single predictors - use the complete readiness criteria panel 1, 6
• Do not use T-piece alone for initial SBT - pressure augmentation has superior outcomes 1, 2
• Remember that 10% of patients who pass SBT still fail extubation - assess cough, secretions, and airway protection 2, 4
• Do not correct hypoxemia with excessive oxygen without treating underlying hypoventilation or atelectasis, especially in chronic hypercapnia 2
• Most SBT failures occur within the first 30 minutes - monitor closely during this period 2

Protocol-Driven Approach

Implement standardized weaning protocols driven by respiratory therapists and ICU nurses, as this approach improves outcomes and reduces mechanical ventilation duration compared to physician-directed weaning alone. 3, 6