Ventilator Management

Ventilator Management

David Ray Velez, MD

Table of Contents

General Management
Oxygenation
Ventilation

See Also:

General Management

General Indications for Mechanical Ventilation

  • Unable to Protect Airway (Trauma, Oropharyngeal Infection, etc.)
  • Hypoxemic Respiratory Failure with Inadequate Oxygenation
  • Hypercapnic Respiratory Failure with Inadequate Ventilation
  • Expectant Course – Anticipated Patient Decline

Primary Goals of Mechanical Ventilation

  • Oxygenation: Provide Oxygen to Lungs and Circulation
  • Ventilation: Exchange of Air Between the Lungs and Environment/Ventilator
    • Most Important Effect: Removal of CO2 from the Body
    • Does Not Increase Blood Oxygen Content

Settings and Modes

Oxygenation

The Goal of Oxygenation is to Avoid Hypoxemia While Using the Lowest Possible Support (PEEP 5 with FiO2 30% is Generally Considered Minimal Support While Ventilated)

General Target Values

  • SaO2/SpO2: > 92% (88% in COPD or ARDS)
  • PaO2: > 60 mmHg (55 mmHg in COPD or ARDS)
  • ScvO2: > 70%

For Severe Acute Hypoxic Events: Disconnect the Ventilator and Use a Bag-Valve-Mask (BVM) to Administer 100% FiO2 Until the Patient Recovers from the Acute Event and Assess for Acute Causes (ETT Dysfunction, PTX, Atelectasis/Mucous Plugging, Bronchospasm, PE)

Adjustments to Increase Oxygenation

  • Most Common Modes (CMV, AC, SIMV):
    • Increase FiO2 (Rapidly Affect Change Within Minutes)
    • Increase PEEP (Can Take Hours to Affect Change – Much Slower)
  • APRV:
    • Increase FiO2
    • Increase P High
    • Increase T High
  • HFOV:
    • Increase FiO2
    • Increase Mean Airway Pressure (MAP)

Adjuncts

Ventilation

The Goal of Ventilation is to Exchange Air Between the Lungs and Environment/Ventilator (Primarily for the Removal of CO2 to Maintain Normal Levels)

  • Ventilation Does Not Increase Blood Oxygen Content

General Target Values

  • PaCO2: 35-45 mmHg
  • Traumatic Brain Injury (TBI): May Consider Hyperventilation (Goal PaCO2: 30-35 mmHg) to Induce Cerebral Vasocontraction
  • Permissive Hypercapnia: Respiratory Acidosis Allowed to Maintain Low Tidal Volumes for the Prevention of Alveolar Overdistention and Barotrauma
    • Anticipated and Generally Well Tolerated
    • pH Goal: 7.30-7.45
      • If pH < 7.30: Increase Rate (Maximum 35 bpm)
      • If pH Remains < 7.15: Can Increase Tidal Volume in 1 ml/kg Increments Until pH > 7.15
    • PaCO2 Goal Not Well Defined

Adjustments to Increase Ventilation (Decrease CO2)

  • Most Common Modes (CMV, AC, SIMV):
    • Increase Rate
      • *COPD Exacerbation Can Cause Auto PEEP/Air Trapping and Increasing the Rate May Actually Worsen Hypercarbia – Decreasing Inspiratory/Expiratory Time Can Improve Ventilation to Remove CO2
    • Increase Tidal Volume (In Volume-Control Modes)
    • Increase Pressure Support (In Pressure-Control Modes)
  • APRV:
    • Increase the Gradient Between P High and P Low
    • Decrease T High
    • Increase T Low
    • *In General, APRV is Avoided if Needing High Ventilatory Requirements
  • HFOV:
    • Decrease Frequency
    • Increase Power/Amplitude (Delta P)
    • Increase Inspiratory Time (I:E Ratio)

Adjustments to Decrease Ventilation (Increase CO2)

  • Most Common Modes (CMV, AC, SIMV):
    • Decrease Tidal Volume (In Volume-Control Modes)
    • Decrease Pressure Support (In Pressure-Control Modes)
    • Decrease Rate
  • APRV:
    • Decrease the Gradient Between P High and P Low
    • Increase T High
    • Decrease T Low
  • HFOV:
    • Increase Frequency
    • Decrease Power/Amplitude (Delta P)
    • Decrease Inspiratory Time (I:E Ratio)