Surgical Critical Care: Supplemental Oxygenation

Supplemental Oxygenation

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.)

Low-Flow Systems

  • Provides Oxygen at Flow Rates Below the Patients Inspiratory Demand
    • Room Air is Therefore Entertained/Mixed & Dilutes the FiO2
    • Exact FiO2 is Extremely Variable
  • Nasal Canula (NC)
    • 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 & Are Uncomfortable
    • Adds Approximately 4% FiO2 Per Additional L/min of Flow
  • Simple Face Mask (Oxygen Mask)
    • Flow Rates: 5-10 L/min
  • Nonrebreather Mask
    • Flow Rates: 10-15 L/min
      • Low-Flow Device with High FiO2
    • Reservoir Bag is Used to Deliver Higher FiO2
    • One-Way Valve Prevents Inhalation of Previously Expired Air

High-Flow Systems

  • Provides Oxygen at Flow Rates that Meet the Patients Inspiratory Demand
    • Entertainment of Room Air is Therefore Minimal with Less Dilution of FiO2
    • Exact FiO2 is Generally More Reliable
  • Venturi Mask
    • Flow Rates: 2-15 L/min
    • Different Sized (Colored) Ports Change the Flow Rate & FiO2 Provided
      • Allows Precise Measurement of Delivered FiO2
    • Often Used in Obstructive Lung Disease When Exact Oxygen Delivery is Important to Not Over-Oxygenate
  • High-Flow Nasal Cannula (HFNC)
    • Adds Humidity & 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)
  • 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

Adjuncts

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

FiO2 of Supplemental Oxygen Devices

  • Room Air: 21% (Regardless of Altitude)
  • Nasal Cannula
    • 1 L/min: 24%
    • 2 L/min: 28%
    • 3 L/min: 32%
    • 4 L/min: 36%
    • 5 L/min: 40%
    • 6 L/min: 44%
  • Simple Face Mask
    • 6 L/min: 35%
    • 7 L/min: 41%
    • 8 L/min: 47%
    • 9 L/min: 53%
    • 10 L/min: 60%
  • Venturi Mask
    • 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%
  • High-Flow Nasal Canula
    • 6 L/min: 47%
    • 10 L/min: 59%
    • 15 L/min: 70%
    • 25 L/min: 83%
    • 60 L/min: 100%
  • Nonrebreather
    • 10 L/min: 60-80%
    • 15 L/min: 95-100%

Supplemental Oxygenation