Version May 2024
INTRODUCTION — Extracorporeal carbon dioxide removal (ECCO2R) is an advanced form of life support that is mostly used in patients with severe hypercapnic respiratory failure without hypoxemia.
This topic will provide an overview of implementation and management of patients receiving ECCO2R. Other extracorporeal life support-relevant topics are found elsewhere:
●(See "Extracorporeal life support in adults in the intensive care unit: Overview".)
●(See "COVID-19: Extracorporeal membrane oxygenation (ECMO)".)
TERMINOLOGY AND PHYSIOLOGY — ECCO2R is a form of extracorporeal life support (ECLS) that is mostly used clinically for temporary support of patients with acute or acute on chronic hypercapnic respiratory failure. Additional terms are described in the table (table 1). Details of ECCO2R and other forms of ECLS are provided separately. (See "Extracorporeal life support in adults in the intensive care unit: Overview", section on 'Terminology'.)
The configuration of the circuit in ECCO2R is comprised of a drainage cannula that removes blood, typically from a large central or peripheral vein. Blood is pumped into a membrane lung where CO2 is removed via the extracorporeal circuit, after which, the blood is reinfused back into the systemic circulation (typically the same or a different vein). Common configurations are discussed below. (See 'Configurations' below.)
ECCO2R is defined physiologically by the intention to primarily remove CO2 in a given patient. As such, if the intention is to remove CO2 without the substantial provision of extracorporeal oxygenation, then the application of ECLS is termed ECCO2R. If oxygenation (in addition to CO2 removal) is the goal of therapy, then the application is extracorporeal membrane oxygenation (ECMO). ECCO2R may be applied at lower blood flow rates on average (typically <2 L/minute) than ECMO and contributes minimally to oxygenation; whereas ECMO, which is delivered at higher blood flow rates (eg, 3 to 7 L/minute), accomplishes both oxygenation and CO2 removal. Further details regarding the determinants of gas exchange are provided separately. (See "Extracorporeal life support in adults in the intensive care unit: Overview", section on 'Determinants of gas exchange'.)
CLINICAL APPLICATIONS — Our approach to selecting patients for venovenous (V-V) extracorporeal membrane oxygenation (ECMO) is discussed in this section. Guidelines that describe the indications and practice of ECLS/ECMO are published by the Extracorporeal Life Support Organization (ELSO) [1,2].
Status asthmaticus — This is the most common application of ECCO2R. ECCO2R is appropriate in patients with status asthmaticus and acceptable oxygenation who have severe, uncompensated respiratory acidosis (eg, pH <7.2) or evidence of excess dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEPi; this includes the presence of barotrauma, such as pneumothorax and pneumomediastinum) despite optimization of medical therapy, invasive mechanical ventilation, and use of sedation with neuromuscular blockade [3]. Conventional management of asthma exacerbations is discussed separately. (See "Acute exacerbations of asthma in adults: Emergency department and inpatient management" and "Invasive mechanical ventilation in adults with acute exacerbations of asthma".)
Oxygenation is classically preserved in this population such that ECMO is uncommonly needed. However, for those in whom oxygenation is inadequate, V-V ECMO is more appropriate than ECCO2R. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)".)
Data to support ECCO2R use in this population are limited to case series that suggest it may be successful as a temporizing measure until the asthma exacerbation resolves [4-9]. As an example, in a series of 26 adults with status asthmaticus, ECCO2R resulted in improved gas exchange, peak airway pressures, and PEEPi, with a high rate of extubation during ECCO2R support (77 percent). All patients survived to discharge. Complications included cannula-associated deep venous thrombosis (23 percent) and bleeding requiring transfusions (15 percent).
End-stage lung disease with ECCO2R as a bridge to lung transplantation — While many patients with severe end-stage lung disease need V-V ECMO to provide both oxygenation and CO2 removal as a bridge to lung transplantation (BTT), a small proportion need only CO2 removal for acute on chronic hypercapnic respiratory failure and are therefore candidates for ECCO2R. ECCO2R under these circumstances can provide temporary support and facilitate patient participation in physical therapy in preparation for transplant. Additional details including timing of ECCO2R and data to support ECLS as a BTT are described separately. (See "Extracorporeal life support in adults in the intensive care unit: Overview", section on 'ECLS as a bridge to an endpoint' and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Severe lung disease with ECMO as a bridge to lung transplantation'.)
General criteria for lung transplant are discussed separately. (See "Lung transplantation: An overview", section on 'Referral for transplant evaluation' and "Lung transplantation: Disease-based choice of procedure", section on 'Disease-based considerations'.)
Investigational considerations — ECCO2R has also been the target of several proposed investigational uses:
●Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) as a means to facilitate early extubation or avoid mechanical ventilation – In patients with AECOPD, ECCO2R, as a means to facilitate early removal of invasive mechanical ventilation or avoid intubation altogether, has been demonstrated to be safe and feasible in nonrandomized studies and is the subject of both ongoing and planned randomized controlled trials [10-14].
●Moderate to severe acute respiratory distress syndrome (ARDS) – ECCO2R is also being investigated as a means of maintaining adequate pH and partial pressure of arterial CO2 (PaCO2) in ventilated patients with ARDS when the goal is to apply an ultra-lung-protective ventilation strategy but when ECMO support is not yet indicated [15]. While pilot data have shown feasibility with such a strategy [16-18], a large randomized trial failed to detect a mortality benefit when ECCO2R-facilitated ultra-lung-protective ventilation was compared with conventional management in patients with moderate to severe acute hypoxemic respiratory failure [19]. This study is discussed in detail separately. (See "Acute respiratory distress syndrome: Ventilator management strategies for adults", section on 'Ventilator strategies of questionable benefit or harm'.)
General evaluation — When evaluating patients who have a potential indication for ECCO2R, we assess candidacy clinically. This clinical evaluation is similar to that described for patients being assessed for V-V or venoarterial (V-A) ECMO. Details of this assessment are provided separately:
Notably, in this population, we also assess the risk of concomitant severe hypoxemia. If patients are believed to be at considerable risk for progression to severe hypoxemia, we place cannulae that are large enough to accommodate both ECCO2R and ECMO, should ECMO be needed to provide substantial oxygenation support at some point. Once the decision is made to proceed, a plan is made for catheter insertion. (See 'Configurations, catheterization, initiation' below.)
Contraindications — Contraindications to ECCO2R are similar to those for ECMO and are listed on the table (table 2). Further details are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Assess contraindications and technical challenges' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'Contraindications (absolute and relative)'.)
CONFIGURATIONS, CATHETERIZATION, INITIATION
Configurations — The most common configuration used in ECCO2R is venovenous (V-V) ECCO2R. We use venous sites similar to those used in V-V extracorporeal membrane oxygenation (ECMO; eg, two-site approach with femoral venous drainage and internal jugular venous reinfusion (figure 1) or a single-site, dual-lumen approach via an internal jugular venous access point (figure 2)). Rarely, we use a low-flow arteriovenous (A-V) approach to ECCO2R (eg, femoral artery as the drainage site and femoral vein as the reinfusion site). This approach relies on native cardiac output rather than an external pump to generate extracorporeal blood flow [20]. Further details regarding V-V ECMO configurations are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Venovenous ECMO configurations and sites'.)
Catheter insertion — Whereas oxygenation in ECMO is largely dependent on the circuit blood flow rate, CO2 removal is primarily determined by the sweep gas flow rate, due to the efficiency with which CO2 transfer occurs across the membrane. Therefore, ECCO2R can be achieved with lower blood flow rates and correspondingly smaller cannulae than what is usually required for oxygenation during ECMO (eg, 20 French drainage and 18 French reinfusion, or smaller). However, if there is an anticipated need for extracorporeal oxygenation, we place larger cannulae to support ECMO, should it be needed at some point during the course of the patient's illness. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Catheter insertion'.)
Initial settings and titration — Following cannulation, the patient is immediately connected to the ECCO2R circuit (typically the pump, membrane lung, and monitor) and sweep gas (a blend of oxygen and air, the fractions of which are determined by the provider and set through a blender) is connected to the membrane lung.
There are no universally agreed upon initial settings. Typical settings are dictated by the degree of support that may be needed and the type of device used. Some devices are designed specifically for "low-flow" ECCO2R (eg, blood flow rates <1 L/minute), whereas other circuits (especially with centrifugal pumps) are optimally designed for >3 L/minute and may exhibit higher rates of hemolysis and other hematologic derangements at lower blood flow rates [21-24]. As an estimate, we typically use the following, achieved incrementally over the first few minutes after initiation:
●Pump speed to achieve an extracorporeal blood flow appropriate to the particular pump (eg, as low as 0.4 L/minute and as high as 3 L/minute or greater).
●Sweep gas flow that typically ranges from 1 to 10 L/minute.
●Fraction of delivered oxygen (FDO2) is typically set to 1.0. However, when there is no intention to provide extracorporeal oxygenation, lower FDO2, or even air (ie, FDO2 0.21), may be used with equally effective CO2 removal.
Immediately following initiation, sweep gas flow is titrated in a similar fashion to that described in V-V ECMO. For those with marked, uncompensated respiratory acidosis (eg, partial pressure of arterial CO2 [PaCO2] >60 mmHg with corresponding acidemia), the sweep gas flow rate should be gradually increased over several hours to avoid complications potentially associated with rapid changes in PaCO2 (eg, intracerebral hemorrhage) [25]. Further details regarding titration are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Initial settings and titration'.)
Factors that determine CO2 removal are shown in the table (table 3).
SUPPORTIVE CARE
Invasive mechanical ventilation — For those receiving ECCO2R for severe asthma exacerbations or as bridge to transplantation, we try to wean patients off of invasive mechanical ventilation and endotracheally extubate them. We maintain pH and partial pressure of arterial CO2 (PaCO2) with the extracorporeal circuit and oxygenation with supplemental oxygen as needed. (See "Initial weaning strategy in mechanically ventilated adults" and "Extubation management in the adult intensive care unit".)
For those patients with evidence of airway obstruction (eg, severe asthma exacerbations or acute exacerbations of chronic obstructive pulmonary disease) who are unable to be endotracheally extubated, we favor a mechanical ventilation strategy that minimizes minute ventilation, with very low respiratory rates (eg, <10) and tidal volumes, with prolongation of the expiratory time, so as to minimize gas trapping and intrinsic positive end-expiratory pressure. We favor prompt discontinuation of neuromuscular blocking agents once ECCO2R has been initiated (if in use prior to ECCO2R) and subsequent minimization of sedation, both of which will help facilitate early endotracheal extubation.
Others — All other supportive care issues that pertain to patients in the intensive care unit receiving ECCO2R, including routine measures and circuit care, are similar to those in patients with venovenous (V-V) extracorporeal membrane oxygenation (ECMO), the details of which are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Supportive therapies' and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Daily assessment and circuit monitoring'.)
There is no consensus on anticoagulation targets for ECCO2R specifically. A reasonable initial target is similar to that for patients on V-V ECMO, but higher targets may be needed. Most experts agree that the lower the blood flow rate applied, the higher the anticoagulation goal should be to minimize the risk of thrombosis. The specific goals will also reflect the particular device used and any known proclivity of the patient for bleeding or clotting. Specific goals for anticoagulation in patients receiving V-V ECMO are discussed separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Anticoagulation'.)
COMPLICATIONS — The complications of ECCO2R are listed in the table (table 4) and are similar to that described for venovenous (V-V) extracorporeal membrane oxygenation (ECMO). Further details regarding the complications of V-V ECMO are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Complications'.)
DEVELOPMENT OF HYPOXEMIC RESPIRATORY FAILURE OR CARDIAC FAILURE — Patients receiving ECCO2R who develop hypoxemic respiratory failure or cardiac failure should be managed medically. Should such therapies fail, our threshold to convert to venovenous or venoarterial extracorporeal membrane oxygenation is low, assuming escalation is both clinically appropriate and concordant with the patient's goals of care. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)" and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)".)
WEANING — Once the underlying disease process has sufficiently improved, we wean ECCO2R. This process is similar to that in venovenous extracorporeal membrane oxygenation with the focus being on maintaining ventilation rather than oxygenation. These details are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Weaning'.)
SUMMARY AND RECOMMENDATIONS
●Terminology – Extracorporeal carbon dioxide removal (ECCO2R) is a form of extracorporeal life support. ECCO2R is mostly used for temporary support of patients with acute or acute on chronic hypercapnic respiratory failure (table 1). The configuration of the circuit in ECCO2R is comprised of a drainage cannula that removes blood, typically from a large central or peripheral vein. CO2 is removed extracorporeally and the blood is reinfused back into the systemic circulation (typically the same or a different vein). (See 'Terminology and physiology' above.)
●Patient selection – Suitable candidates for ECCO2R are the following:
•Patients with status asthmaticus and acceptable oxygenation who have severe, uncompensated respiratory acidosis (eg, pH <7.2) or evidence of excess dynamic hyperinflation and intrinsic positive end-expiratory pressure (this includes the presence of barotrauma, such as pneumothorax and pneumomediastinum) despite optimization of medical therapy, invasive mechanical ventilation, and use of sedation with neuromuscular blockade. (See 'Status asthmaticus' above.)
•Patients with acute on chronic hypercapnic respiratory failure due to end-stage lung disease who are candidates for lung transplantation. (See 'End-stage lung disease with ECCO2R as a bridge to lung transplantation' above and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Severe lung disease with ECMO as a bridge to lung transplantation'.)
•Contraindications to ECCO2R are similar to those for venovenous (V-V) extracorporeal membrane oxygenation (ECMO) and are listed on the table (table 2). These contraindications are discussed separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Assess contraindications and technical challenges'.)
●Procedural issues and initiation – The most common configuration used is V-V ECCO2R. Catheter insertion is similar to that in V-V ECMO, but smaller cannulae may be used (eg, 20 French drainage and 18 French reinfusion, or smaller) when there is no anticipated expectation of needing ECMO for oxygenation support at some point during the patient's illness. (See 'Configurations, catheterization, initiation' above and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Catheter insertion'.)
Following cannulation, the patient is immediately connected to the ECCO2R circuit. Although variable, typical initial settings are the following (see 'Initial settings and titration' above):
•Pump speed to achieve an extracorporeal blood flow appropriate to the particular pump (eg, 0.4 L/minute to 3 L/minute or greater).
•Sweep gas flow that typically ranges from 1 to 10 L/minute.
•Fraction of delivered oxygen (FDO2) is typically set to 1.0, although lower FDO2, or even air (ie, FDO2 0.21) may be used with equally effective CO2 removal when clinically appropriate.
Immediately following initiation, sweep gas flow is titrated slowly in order to lower the partial pressure of arterial CO2 (PaCO2) and increase the pH in a similar fashion to that described in V-V ECMO. (See 'Initial settings and titration' above and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Initial settings and titration'.)
●Supportive care and daily assessment – Supportive care and daily assessment are similar to that in V-V ECMO with the following exceptions (see "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Supportive therapies' and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Daily assessment and circuit monitoring'):
•Mechanical ventilation – Mechanical ventilation is typically weaned with the goal of endotracheal extubation (eg, 24 to 48 hours) while managing PaCO2 and pH with the extracorporeal circuit and oxygenation with the provision of supplemental oxygen as needed. (See "Initial weaning strategy in mechanically ventilated adults" and "Extubation management in the adult intensive care unit".)
•Anticoagulation – All patients require anticoagulation due to the high risk of thrombosis. A reasonable initial target is similar to that for patients on V-V ECMO. However, in some cases, higher targets are needed. While there is no consensus on anticoagulation targets for ECCO2R specifically, most experts agree that the lower the blood flow rate applied, the higher the anticoagulation goal should be to minimize the risk of thrombosis. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Anticoagulation'.)
●Complications – The complications of ECCO2R are listed in the table (table 4) and similar to that described for V-V ECMO, the details of which are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Complications'.)
●Weaning – Once the underlying disease process has sufficiently improved, we wean ECCO2R. This process is similar to that in V-V ECMO with the focus on ventilation rather than both ventilation and oxygenation. These details are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Weaning'.)
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