Ventilator Liberation

Ventilator Liberation

David Ray Velez, MD

Table of Contents

Definitions
Readiness Testing
Weaning
Extubation

Definitions

Ventilator Liberation: The Entire Three-Step Process of (1) Evaluating a Patient’s Readiness, (2) Weaning the Ventilator, and (3) Eventual Extubation

Readiness Testing: Objective Criteria to Determine if a Patient is Ready to Begin Weaning

Weaning: Decreasing the Degree of Ventilatory Support to Evaluate the Likelihood of Successful Extubation

Extubation: Physical Removal of the Endotracheal Tube

Readiness Testing

Readiness Testing: Objective Criteria to Determine if a Patient is Ready to Begin Weaning

Readiness Requirements

  • Improvement in Underlying Cause of Respiratory Failure
  • Adequate Oxygenation (SpO2 > 88-90% with FiO2 < 40-50% and PEEP ≤ 5-8 cm H2O)
  • Arterial pH > 7.25
  • Hemodynamic Stability (Stable Low Dose Vasopressors are Not an Absolute Contraindication)
  • Ability to Take Spontaneous Respirations

Other Considerations

  • Easily Arousable Mental Status, Able to Protect the Airway
  • Hemoglobin ≥ 7.0 mg/dL (Anemia Inhibits Oxygen Delivery)
  • Afebrile (Fever Increases Minute Ventilation and Work of Breathing)
  • Diaphragmatic Ultrasound (Diaphragm Excursion or Diaphragmatic Thickening Fraction) May Predict Weaning Success

If Not Ready to Wean: Continue to Manage Any Underlying Disorders Until Readiness Criteria are Met – May Require Consideration for Long-Term Mechanical Ventilation and Tracheostomy if Persistently Fails to Improve

Weaning

Weaning: Decreasing the Degree of Ventilatory Support to Evaluate the Likelihood of Successful Extubation

Spontaneous Breathing Trial (SBT)

  • Definition: Trial of Spontaneous Patient Breathing Off of Controlled Ventilation to Determine Likelihood of Successful Extubation
    • Trials Performed for 30 Minutes-2 Hours with Minimal Ventilatory Support
  • Minimal Ventilatory Support
    • Techniques:
      • Pressure Support Ventilation (PSV) – Pressure Support 5-8 cm H2O with PEEP 5 cm H2O
      • Automatic Tube Compensation
      • Volume Support Ventilation (VSV)
      • Continuous Positive Airway Pressure (CPAP) – PEEP 5 cm H2O
    • Given to Overcome the Resistance of the Endotracheal Tube
  • SBT is the Most Commonly Used Weaning Method
  • 50-75% Pass the Initial SBT
  • SBT’s Should be Performed Daily Once Deemed Ready for Weaning

Less Common Weaning Approaches

  • Gradual PSV Weaning – During Pressure-Support Ventilation (PSV) the Level of Pressure Support Starts High and is Gradually Decreased
  • SIMV Weaning – Synchronized Intermittent Mandatory Ventilation (SIMV) with a Gradual Decrease in the Frequency and Level of Support of Ventilator-Assisted Breaths
  • Automated PSV Weaning – Computer Systems Automatically Adjust the Level of Pressure Support to Maintain Normal Parameters (Tidal Volume, Rate, and ETCO2) While Gradually Reducing the Pressure Support Provided
  • Extubation with Immediate Application of Non-Invasive Positive Pressure Ventilation (NIPPV) – May Consider if Failing SBT with High Risk for Further Difficulty Weaning and Extubating Such as Patients with COPD
  • *See Ventilator Modes

Weaning Predictors of Success/Failure

  • Best Predictor of Success: Spontaneous Breathing Trial (SBT)
  • Rapid Shallow Breathing Index (RSBI)
    • RSBI = Respiratory Rate / Tidal Volume
    • Excellent Predictor of Failing but Poor Predictor of Success
    • RSBI ≥ 105 Breaths/min/L Predicts Weaning Failure
    • *Generally Considered the Best Parameter Outside of the SBT
  • Other Poor Predictors:
    • Negative Inspiratory Force (NIF)/Maximal Inspiratory Pressure (MIP/PImax)
      • NIF < -30 (More Negative) Indicates Weaning Success
      • Indicates Good Inspiratory Strength
      • Predicts Failing Better than Success
    • PaO2/FiO2 (P:F Ratio)
    • PaO2/PAO2
    • Alveolar-Arterial (A-a) Oxygen Gradient
    • Compliance
  • Integrative Indices:
    • Accuracy of Indices are Variable and Some Variables May Be Difficult to Obtain
    • CROP Index
      • CROP (Compliance, Rate, Oxygenation, Pressure)
      • CROP = [Cdyn x MIP x (PaO2/PAO2)] / RR
        • Cdyn = Dynamic Compliance
        • MIP = Maximal Inspiratory Pressure
        • PaO2 = Arterial Partial Pressure of Oxygen
        • PAO2 = Alveolar Partial Pressure of Oxygen
        • RR = Respiratory Rate
      • CROP > 13 Indicates Weaning Success
    • CORE Index
      • CORE (Compliance, Oxygenation, Respiration, Effort)
      • Modification of the CROP Index
      • CORE = [Cdyn x (MIP/P0.1) x (PaO2/PAO2)] / RR
        • Cdyn = Dynamic Compliance
        • MIP = Maximal Inspiratory Pressure
        • 1 = Airway Pressure 0.1 Seconds After the Start of Inspiratory Flow
        • PaO2 = Arterial Partial Pressure of Oxygen
        • PAO2 = Alveolar Partial Pressure of Oxygen
        • RR = Respiratory Rate
      • CORE > 8 Indicates Weaning Success
    • Integrative Weaning Index (IWI)
      • IWI = (Cst,rs) x SaO2 / (f/Vt)
        • Cst,rs = Static Compliance of the Respiratory System
        • SaO2 = Arterial Oxygen Saturation
        • f/Vt = RSBI = Respiratory Rate / Tidal Volume
      • IWI > 25 Indicates Weaning Success

Cuff Leak

  • Definition: The Loss of Air Around the Endotracheal Tube Upon Expiration When the Cuff is Deflated
  • Positive Leak Definitions:
    • Audible Sound of Air Movement Around the Tube
    • Leak ≥ 110 cc or ≥ 25% Inspired Tidal Volume as Measured on the Ventilator
  • Positive Cuff Leak is Not a Predictor of Successful Extubation
  • Negative Leak Indicates Swelling Around the Tube and Risk for Post-Extubation Stridor
  • Management of a Negative Leaks:
    • Give Steroids Prior to Extubation to Decrease the Risk of Post-Extubation Stridor and Reintubation
    • Consider 20 mg IV Methylprednisolone Every 4 Hours for 12 Hours Prior to Extubation
    • Wait At Least 4-6 Hours Before Extubation

Extubation

Extubation: Physical Removal of the Endotracheal Tube

Technique

  • Place into an Upright Position
  • Suction the Oral Cavity and Lower Airway
  • Release All Ties and Securement Devices
  • Deflate the Endotracheal Cuff
  • Remove the Tube While Patient Exhales or Coughs
  • Transition to Alternative Source of Supplemental Oxygen (Nasal Cannula or Face Mask)
    • If at a High-Risk for Reintubation, Consider High-Flow Nasal Cannula (HFNC) or Bilevel Positive Airway Pressure (BPAP) to Reduce the Risk for Reintubation

Unplanned Extubation

  • Frequency: 3-12% of All Intubated Patients
  • Risk Factors:
    • Poor Endotracheal Tube Securement
    • Low Level of Sedation
    • Agitation
    • Physically Restrained
  • Most Occur Within One Day of a Planned Extubation
  • Most are Deliberately Removed by the Patient (Not Accidental)
  • Unplanned Extubations Require a Low Threshold for Immediate Reintubation if Indicated
  • About 50% Require Reintubation, Often Within the First 12 Hours

Failed Extubation (Requires Reintubation)

  • Reported Rates: 6-20%
  • “Optimal” Rate: 5-10%
    • Higher Rates May Indicate that the Physician is Extubating Too Soon
    • Lower Rates May Indicate that the Physician is Waiting Too Long to Attempt Extubation (Increased Risk of Ventilator-Associated Complications)