Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

Types of Extracorporeal Life Support (ECLS)


  • Cardiopulmonary Bypass (CPB) (see Cardiopulmonary Bypass)
  • Extracorporeal CO2 Removal (ECCO2R): originally developed by Gattinoni (JAMA, 1986) [MEDLINE]
  • Extracorporeal Membrane Oxygenation (ECMO)

Differences Between Cardiopulmonary Bypass and Extracorporeal Membrane Oxygenation (ECMO) (see Cardiopulmonary Bypass)

  • Cardiopulmonary Bypass is Equipped with Reservoir Into Which Blood from the Heart is Drained: allows a bloodless surgical field for valve and aortic operations
    • In Contrast, the ECMO Circuit Does Not Contain a Reservoir, So Blood Flow Needs to Be Continuous
  • Cardiopulmonary Bypass Can Be Utilized in Conjunction with Air Vent Tubing, Cardioplegia Line for Myocardial Preservation, or Cell Salvage Tubing
  • Requirement for Systemic Heparin Anticoagulation is Less Intense for ECMO Because Blood Flow is Continuous and There is No Blood-Air Interface in the Reservoir
    • Higher Flow Rates of >4 L/min are Used During ECMO (in Contrast to the Lower Flow Rates of 2 L/min Used During CPB)
    • However, Continuous Anticoagulation is Necessary to Prevent Thrombus Formation on the Synthetic Thrombogenic Surfaces of Both CPB and ECMO
  • ECMO Circuits are Designed for Longer-Term Use (May Be Used for Weeks, Depending on the Life of the Membrane Oxygenator), While CPB Use is Designed for Use for a Period of Hours


General Comments

Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)

Clinical Efficacy

Criteria to Start Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)



Relative (NEJM, 2011) [MEDLINE]


Blood Flow Rate During VV-ECMO

Oxygenation During VV-ECMO

Mixture Between Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO) Oxygenated Blood Flow and the Patient’s Native Venous Blood Flow

  • Background
    • In Severe ARDS with VV-ECMO, the Lungs Contribute Little or Nothing to Gas Exchange and the Oxygen Saturation and Carbon Dioxide Levels of the Blood in the Right Ventricle is the Summation of Mixing of Oxygenated ECMO Blood with Deoxygenated Native Venous Blood
      • Due to the Lack of Meaningful Lung Function, The Blood in the Right Ventricle Will Have the Same Oxygen Saturation and Carbon Dioxide Levels of the Blood on the Arterial Side of the Circulation
    • Mixing Point
      • Single (Avalon Catheter, Crescent Catheter) Catheter Setup (Inserted Via the Right Internal Jugular Vein): mixing point occurs in the right atrium
      • Double Catheter Setup

Calculation of the Oxygen Delivery/Oxygen Consumption Ratio

  • General Comments
    • Calculation of the Oxygen Delivery/Oxygen Consumption Ratio is a Standard Means to Determine if Oxygen Delivery is Adequate in Patient on VV-ECMO
      • This Calculation is Critical Since the Arterial pO2 May Be Significantly Lower than the pO2 of a Patient in ARDS Who is Not on VV-ECMO
      • These Low pO2 Values May Alarm Staff Who are Used to Meeting Specific pO2 Goals in Patients in ARDS
      • In a Patient on VV-ECMO, the Oxygen Delivery/Oxygen Consumption Ratio Goal is More Clinically Relevant (than the Arterial pO2) in Maintaining Tissue Oxygenation
  • Step 1: Calculation of Oxygen Content of Arterial Blood, Pre-Oxygenator (Venous) Blood, and Post-Oxygenator Blood
    • Arterial Oxygen Content = 13.4 x Hemoglobin x Arterial SaO2 + (Arterial pO2 x 0.031)
    • Pre-Oxygenator Oxygen Content = 13.4 x Hemoglobin x Pre-Oxygenator SaO2 + (Pre-Oxygenator pO2 x 0.031)
    • Post-Oxygenator Oxygen Content = 13.4 x Hemoglobin x Post-Oxygenator SaO2 + (Post-Oxygenator pO2 x 0.031)
    • Terms
      • Constant 13.4 mL O2/g Hb: accounts for the fact that 1.34 ml of O2 is carried per g of Hb (13.4 is used in the equation to correct the units from dL to L)
        • The Normal Oxygen Carrying Capacity is 1.39 ml O2 per g of Hb
        • However, Due to the Presence of Abnormal Hemoglobins (Such as Carboxyhemoglobin and Methemoglobin), this Value is Decreased to 1.34 ml O2 per g of Hb
      • Hemoglobin: in g/dL
      • SaO2: as decimal
      • pO2: in mm Hg
      • Constant 0.0031 mL O2/L/mm Hg: solubility coefficient of oxygen at body temperature
  • Step 2: Calculation of Flows
    • General Comments
      • When Two Blood Flows Containing Different Oxygen Contents Mix, the Resultant Oxygen Content is the Average of the Amount of Oxygen Content in Each of the Two Flows (Not the Average of the Partial Pressures of Oxygen, i.e. the pO2’s) (Extracorporeal Life Support: The ELSO Red Book (5th Edition, 2017) [LINK]
    • Total Oxygen Content = [(Post-Oxygenator Oxygen Content x VV-ECMO Flow)/Total Flow] + [(Pre-Oxygenator Oxygen Content x Native Venous Flow)/Total Flow]
      • Assumes No Native Lung Function
    • Solving for Total Flow (i.e. Total Cardiac Output)
      • Total Flow = VV-ECMO Flow [(Post-Oxygenator Oxygen Content – Pre-Oxygenator Oxygen Content)/(Arterial Blood Oxygen Content – Pre-Oxygenator Oxygen Content)]
    • Solving for Native Venous Flow
      • Native Venous Flow = Total Flow = VV-ECMO Flow
  • Step 3: Calculation of Oxygen Delivery (DO2)/Oxygen Consumption (VO2) Ratio (see Hypoxemia)
    • Oxygen Delivery = [Arterial Oxygen Content] x CO = [Hb x 13.4 x SaO2 + (pO2 x 0.0031)] x CO
      • Hemoglobin (Hb): in g/dL
      • Constant 13.4: accounts for the fact that 1.34 ml of O2 is carried per g of Hb (13.4 is used in the equation to correct the units from dL to L)
      • Arterial Oxygen Saturation (SaO2): as a decimal
      • Thermodilution-Measured Cardiac Output (CO) (from Swan-Ganz Catheter, etc) or Flow: in L/min
      • Normal Arterial Oxygen Content: approximately 200 mL O2/L (or 20 mL O2/dL)
        • Note: the Equation Used Here Yields the Arterial Oxygen Content in mL O2/L, Which Allows the Arterial Oxygen Content Value to Be Plugged into the Oxygen Delivery Equation without Unit Conversion
      • Normal Oxygen Delivery (Using Cardiac Output = CO): approximately 1000 mL O2/min
    • Calculation of Approximate Oxygen Consumption
      • Oxygen Consumption = Weight (in kg) x 3 mL O2/kg/min
    • Calculation of the Oxygen Delivery (DO2)/Oxygen Consumption (VO2) Ratio
  • Recommendations (Extracorporeal Life Support: The ELSO Red Book (5th Edition, 2017) [LINK]
    • Maintain Oxygen Delivery/Oxygen Consumption Ratio >3
      • In Sepsis Where Cardiac Output is Typically Elevated, This 3:1 Ratio Can Only Be Maintained if Flow is Augmented

Factors Contributing to Hypoxemia During VV-ECMO (Excluding Equipment Failure)

Strategies to Improve Systemic Oxygenation During VV-ECMO



Vascular Access

Avalon Catheter Placement into the Right Internal Jugular (IJ) Vein (Avalon Laboratory, Los Angeles, CA, USA)


Extracorporeal Life Support Organization (ELSO) Guidelines for Adult Respiratory Failure v1.3 (2013) [LINK]

Management (Extracorporeal Life Support Organization (ELSO) Guidelines for Adult Respiratory Failure v1.3, 2013) [LINK]

Adjustments To Increase the Arterial pO2

Adjustments To Change the Arterial pCO2

Maintenance of a Near-Normal Hematocrit

Ventilator Management During Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

Addition of Prone Positioning to VV-ECMO Therapy

Use of Combination Continuous Venovenous Hemodialysis (CVVHD) with Venovenous Extracorporeal Membrane Oxygenation (ECMO)

Monitoring of Arterial Oxygen Saturation and pO2 During VV-ECMo

Adverse Effects/Complications (NEJM, 2011) [MEDLINE]