Key Takeaways
- Weaning readiness criteria: underlying cause resolved, FiO2 ≤0.40, PEEP ≤5-8 cmH2O, hemodynamically stable, able to initiate breaths
- Rapid Shallow Breathing Index (RSBI) = f/VT; RSBI <105 breaths/min/L predicts successful extubation
- Negative Inspiratory Force (NIF or MIP): more negative than -20 to -30 cmH2O indicates adequate respiratory muscle strength
- Spontaneous Breathing Trial (SBT) is the gold standard for predicting extubation success; typically 30-120 minutes
- SBT methods: T-piece trial, low-level PSV (5-8 cmH2O), or CPAP with minimal support
- SBT failure criteria: RR >35, SpO2 <90%, HR change >20%, BP change >20%, agitation, diaphoresis
- The cuff leak test helps predict post-extubation stridor; absence of leak suggests laryngeal edema
- Post-extubation care includes monitoring for stridor, racemic epinephrine for laryngeal edema, and keeping reintubation equipment at bedside
Weaning & Liberation from Mechanical Ventilation
Weaning and liberation from mechanical ventilation is a critical process that affects patient outcomes, ICU length of stay, and hospital costs. The TMC exam tests your understanding of weaning readiness criteria, weaning parameters, spontaneous breathing trials, and extubation protocols.
Weaning Readiness Assessment
Before initiating a weaning trial, the following criteria should be met:
| Criterion | Requirement |
|---|---|
| Underlying cause | Resolving or resolved |
| Oxygenation | FiO2 ≤0.40, PEEP ≤5-8 cmH2O, PaO2 ≥60 mmHg |
| Hemodynamics | Stable BP, no vasopressors or low-dose only |
| Neurological | Alert, able to follow commands, adequate cough/gag |
| Respiratory drive | Patient initiating breaths spontaneously |
| Acid-base | pH 7.25-7.50 |
| Temperature | No significant fever (T <38.5 C) |
| Sedation | Sedation minimized or off; SAT (spontaneous awakening trial) passed |
Key Weaning Parameters
| Parameter | Criteria for Weaning | What It Measures |
|---|---|---|
| RSBI (Rapid Shallow Breathing Index) | <105 breaths/min/L | f/VT ratio; balance of respiratory demand vs. capacity |
| NIF/MIP (Negative Inspiratory Force) | More negative than -20 cmH2O | Inspiratory muscle strength |
| Vital Capacity (VC) | >10-15 mL/kg IBW | Ability to take a deep breath; cough effectiveness |
| Spontaneous VT | >5 mL/kg IBW | Adequate tidal volume without support |
| Spontaneous RR | <35 breaths/min | Breathing not too rapid (respiratory distress) |
| Minute Ventilation (VE) | <10 L/min | Total ventilatory demand is manageable |
| PaO2/FiO2 (P/F) ratio | >150-200 | Adequate oxygenation on minimal support |
| Maximum Voluntary Ventilation (MVV) | 2x resting VE | Ventilatory reserve |
The RSBI — Most Important Weaning Predictor
The Rapid Shallow Breathing Index (RSBI) is the most commonly used and tested weaning predictor:
RSBI = Respiratory Rate (f) / Tidal Volume in liters (VT)
- RSBI <105: Predicts successful extubation (~80% positive predictive value)
- RSBI >105: Predicts weaning failure (rapid, shallow breathing = high rate, low VT)
- Measured during 1 minute of unassisted spontaneous breathing (CPAP 0 or T-piece)
Example: A patient breathes at 24 breaths/min with a VT of 0.35 L:
- RSBI = 24 / 0.35 = 69 → Favorable for weaning
Spontaneous Breathing Trial (SBT)
The SBT is the gold standard for predicting extubation success:
| SBT Parameter | Details |
|---|---|
| Duration | 30-120 minutes |
| Methods | T-piece trial, PSV 5-8 cmH2O + PEEP 5, CPAP 5 |
| Monitoring | Continuous SpO2, HR, BP, RR, subjective comfort |
SBT Failure Criteria (return to full support if any occur):
- Respiratory rate >35 breaths/min
- SpO2 <90% (or drop >4% from baseline)
- Heart rate change >20% from baseline (tachycardia or bradycardia)
- Systolic BP >180 mmHg or <90 mmHg
- Agitation, anxiety, or diaphoresis
- Paradoxical breathing or accessory muscle use
- VT <4 mL/kg IBW
Extubation Protocol
Pre-extubation checklist:
- Passed SBT for 30-120 minutes
- Adequate cough strength (able to generate secretion clearance)
- Manageable secretion volume (not requiring frequent suctioning)
- Positive cuff leak test (air escapes around deflated cuff = no significant laryngeal edema)
- NPO or low aspiration risk
- Reintubation equipment at bedside
Post-extubation monitoring:
- Monitor for stridor (laryngeal edema) — typically occurs within 24-48 hours
- Administer racemic epinephrine nebulization for stridor if it develops
- Consider IV corticosteroids pre-extubation in high-risk patients (>4 days intubated, traumatic intubation)
- Have BiPAP or HFNC available as rescue therapy
- Keep reintubation equipment readily available for 24-48 hours
A patient on mechanical ventilation has the following weaning parameters: RR 22, spontaneous VT 0.28 L, NIF -32 cmH2O. What is the RSBI and does it predict successful weaning?
During a spontaneous breathing trial (SBT), the patient develops a respiratory rate of 38, SpO2 of 87%, and visible accessory muscle use. The respiratory therapist should:
The cuff leak test is performed prior to extubation to assess for:
A patient who was recently extubated develops inspiratory stridor within 2 hours. The MOST appropriate initial intervention is:
Place the steps of the weaning and extubation process in the correct order.
Arrange the items in the correct order
A patient has the following weaning parameters: RR 34, spontaneous VT 0.18 L, NIF -15 cmH2O. What is the RSBI and does this patient meet weaning criteria?
Which SBT method involves disconnecting the patient from the ventilator and having them breathe through the endotracheal tube connected to a humidified oxygen source?