Ventilator Settings

Ventilator Settings

David Ray Velez, MD

Table of Contents

Typical Initial Settings
Basic Settings
Advanced Settings

Typical Initial Settings

Basic Settings

  • Rate: 8-12 Breaths per Minute
    • May Start Higher for a Patient Being Intubated with Acidosis and Tachypnea
  • Tidal Volume: 8 ml/kg x Ideal Body Weight
    • Lung Protective Strategy: 4-6 ml/kg x Ideal Body Weight
  • Pressure Support: 5-10 cm H2O
    • Generally Avoid Pressures > 20 cm H2O or PIP > 30-35
  • PEEP: 5-8 cm H2O
  • FiO2: 100% and Titrate Down Off ABG and Pulse Oximetry as Able

Advanced Settings

  • Trigger Sensitivity: -2 cm H2O
  • I/E Ratio: 1:2 or 1:3
  • Inspiratory Flow Rate: 60 L/min

Basic Settings

Rate (f/RR)

  • Definition: Number of Breaths Delivered per Minute
  • Excessively High Rates are Uncomfortable and Cause Decreased Exhalation Time Which Can Cause Increased Mean Airway Pressure and Air Trapping
  • “Over-Breathing the Vent”: Refers to When a Patient is Taking More Spontaneous Patient-Triggered Breaths at a Rate Beyond the Set Rate on the Ventilator

Tidal Volume (Vt)

  • Used in Volume Controlled Modes
  • Definition: Volume of Air Delivered with Each Breath
  • Excessively High Volumes Increase Pressure Which Causes Barotrauma

Pressure Support (PS)

  • Also Known as “Inspiratory Pressure (PI)” or “Change in Pressure (∆P)”
  • Used in Pressure Controlled Modes
  • Definition: Additional Pressure Added to PEEP to Cause Inspiration
  • Excessively High Pressure Causes Barotrauma
  • *Different Ventilator Manufacturers May Use Peak Inspiratory Pressure (PIP) Instead
    • Peek Inspiratory Pressure (PIP): Highest Pressure Seen During Inspiration
    • PIP = PI + PEEP

Positive End Expiratory Pressure (PEEP)

  • Definition: Positive Pressure Remaining in the Airways at the End of Expiration
  • Effects:
    • Increased Alveolar Recruitment (Prevents Collapse to Maximize Oxygen Transfer)
    • Increased Functional Residual Capacity (FRC)
    • Increased Compliance
  • Complications:
    • Increased Mean Airway Pressure
    • Increased Pulmonary Vascular Resistance Causes Increased Right Atrial Pressure
    • Increased Right Atrial Pressure Decreases Venous Return (Preload) and Cardiac Output
  • Auto/Intrinsic PEEP (Air Trapping)

Fraction of Inspired Oxygen (FiO2)

  • Definition: Percentage of Oxygen in Air Delivered to the Patient
  • FiO2 of Room Air: 21% (Regardless of Altitude)
  • Oxygen Toxicity:
    • High Oxygen Levels Produce Reactive Oxygen Species (ROS)
    • Lorraine Smith Effect – Lung Damage Occurs with High FiO2 (> 60%) for a Prolonged Period of Time (> 24 Hours)
    • Paul Bert Effect – CNS Toxicity from High FiO2 Over a Short Period of Time When Barometric Pressure is High (1.6-4.0 ATA)

Advanced Settings

Trigger Sensitivity

  • Definition: The Negative Pressure Required to Initiate a Patient-Triggered Breath
  • Normal Setting: -2 cm H2O
  • If Too High: Weak Patients are Unable to Trigger Breaths
    • Patients with High Auto-PEEP May Have Difficulty Inhaling Enough to Activate the Trigger
  • If Too Low: Machine will Auto-Cycle Causing Overinflation
    • Issues May Arise in the Diagnosis of Brain Death if Noting Spontaneous Breaths that are Caused by a Low Trigger Setting and are Not Due to a True Inspiratory Effort
  • Causes of Auto-Triggering:
    • Coughing
    • Hiccups
    • Shivering
    • Seizures
    • Strong Cardiogenic Oscillators
    • Condensation in the Ventilator Circuit (“Rain Out”)

Inspiratory/Expiratory (I/E) Ratio

  • Definition: Ratio of Inspiratory Time to Expiratory Time
  • Normal Settings: 1:2 or 1:3
  • Patients with Airflow Limitation (Asthma/COPD Exacerbation) Should Have Ratios ≥ 1:4 to Limit Auto-PEEP (Need Longer Expiration Time)
  • Either I/E Ratio or Inspiratory Flow Rate Can be Adjusted – But Not Both

Inspiratory Flow Rate

  • Definition: Rate of Air Flow Delivered During Inspiration
  • Normal Settings: 60 L/min
  • Patients with Airflow Limitation (Asthma/COPD Exacerbation) Can Have the Rate Increased Up to 120 L/min to Limit Auto-PEEP
  • Either I/E Ratio or Inspiratory Flow Rate Can be Adjusted – But Not Both (Serve Same Function)

Inspiratory Flow Waveforms

  • Definition: Negative Pressure Required to Initiate a Patient-Triggered Breath
  • Square/Constant Waveform: Flow Rate Remains Constant During Inspiration
    • Lower Mean Airway Pressure
    • May Be Preferred in Isolated TBI (Lower Pressure Allows Improved Cerebral Venous Drainage)
  • Decelerating Waveform: Flow Rate is Highest at Initiation but Decreases Throughout Inspiration
    • Lower Peak Airway Pressure
    • Higher Mean Airway Pressure
      • Improved Oxygenation
      • Can Decrease Venous Return and Cardiac Output
    • Longer Inspiratory Time
    • Shorter Expiratory Time
      • Higher Risk for CO2 Retention and Air Trapping (Especially in COPD)

Inspiratory Flow Waveform