Supplemental Oxygenation

Supplemental Oxygenation

David Ray Velez, MD

Table of Contents

Definitions
Systems
Clinical Use

Definitions

Low-Flow Systems

  • Definition: Provides Oxygen at Flow Rates Below the Patients Inspiratory Demand
  • Room Air is Therefore Entertained (Mixed) and Dilutes the FiO2
  • Exact FiO2 is Extremely Variable
  • Systems:
    • Nasal Canula (NC)
    • Simple Face Mask (Oxygen Mask)
    • Venturi Mask
    • Nonrebreather Mask

High-Flow Systems

  • Definition: Provides Oxygen at Flow Rates that Meet the Patients Inspiratory Demand
  • Entertainment of Room Air is Minimal with Less Dilution of FiO2
  • Exact FiO2 is Generally More Reliable
  • Systems:
    • High-Flow Nasal Cannula (HFNC)
    • Mechanical Ventilator
    • Rebreather – Used in Scuba Diving but Not Medical Practice

Systems

Room Air

  • FiO2: 21% (Regardless of Altitude)
  • Other Contents:
    • 78% Nitrogen
    • 1% Other Trace Gasses (CO2, Hydrogen, Neon)
    • Aerosols – Tiny Nongaseous Particles (Dust, Pollen, etc.)

Nasal Canula (NC)

  • The Most Common Device Used
  • Simply Provides Increased Flow of Oxygen Through Tubes into the Nostrils
  • Flow Rates: 1-6 L/min
    • Rates Over 6 L/min Dry Mucous Membranes and Are Uncomfortable
  • Supplemental FiO2:
    • 1 L/min: 24%
    • 2 L/min: 28%
    • 3 L/min: 32%
    • 4 L/min: 36%
    • 5 L/min: 40%
    • 6 L/min: 44%
  • *Adds Approximately 4% FiO2 Per Additional L/min of Flow

Simple Face Mask (Oxygen Mask)

  • Flow Rates: 5-10 L/min
  • Supplemental FiO2:
    • 6 L/min: 35%
    • 7 L/min: 41%
    • 8 L/min: 47%
    • 9 L/min: 53%
    • 10 L/min: 60%

Venturi Mask

  • Flow Rates: 2-15 L/min
  • Different Sized (Colored) Ports Change the Flow Rate and FiO2 Provided
    • Allows Precise Measurement of Delivered FiO2
  • Often Used in Obstructive Lung Disease When Exact Oxygen Delivery is Important to Not Over-Oxygenate
  • Supplemental FiO2:
    • Blue Valve (2 L/min): 24%
    • White Valve (4 L/min): 28%
    • Orange Valve (6 L/min): 31%
    • Yellow Valve (8 L/min): 35%
    • Red Valve (10 L/min): 40%
    • Green Valve (15 L/min): 60%

Nonrebreather Mask

  • A Low-Flow Device with High FiO2
  • Flow Rates: 10-15 L/min
  • Reservoir Bag is Used to Deliver Higher FiO2
  • One-Way Valve Prevents Inhalation of Previously Expired Air
  • Supplemental FiO2:
    • 10 L/min: 60-80%
    • 15 L/min: 95-100%
  • Rebreather – Used in Scuba Diving but Not Medical Practice
    • Mask with a Reservoir but No One-Way Valve
      • Expired Air Dilutes the Inspired Oxygen
    • Although Considered “High-Flow” the FiO2 is Much Lower than Nonrebreather Masks

High-Flow Nasal Cannula (HFNC)

  • Adds Humidity and Heat to Allow High Flow Rates (Up to 60 L/min)
  • Additional Advantages:
    • Reduced Anatomical Dead Space
    • Provide Small Amount of CPAP/PEEP (4-5 cm H2O)
    • Minimizes Mixing of Room Air – Increased FiO2 is More Reliable
  • Some Evidence Suggests HFNC May Be More Effective than Standard Oxygen Supply Devices (Nonrebreather)
  • Supplemental FiO2:
    • 6 L/min: 47%
    • 10 L/min: 59%
    • 15 L/min: 70%
    • 25 L/min: 83%
    • 60 L/min: 100%

Supplemental Oxygenation

Clinical Use

General Target Values

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

Step-Up Approach

  • Generally Begin with Low-Flow Systems and Advance as Necessary
  • Start with Nasal Cannula (The Most Widely Used and Rapidly Available)
  • If Nasal Cannula is Insufficient: Step Up to a Nonrebreather Mask
    • Face Mask Only Provides Minimal Improvement in FiO2
    • Venturi Mask Also Only Provides Minimal Improvement in FiO2 and is Generally Used in More Specific Scenarios
  • If Low-Flow Systems are Insufficient: Step Up to a High Flow System
    • High-Flow Nasal Cannula Can Potentially Avoid Intubation
    • Consider Intubation and Mechanical Ventilation if Indicated

Supplemental Humidity

  • Problems with Dry Air:
    • Can Cause Inflammation and Damage, Increasing Airway Resistance
    • Less Comfortable
    • Increased Water Loss
    • Decreased Mucociliary Clearance
  • Adjuncts:
    • Supplemental Humidity – Can Be Connected to Any Flow Meter to Provide Moisture
    • Opening Mouth – Can Also Add Humidity