Extracorporeal life support (ECLS) is a highly specialized form of life-sustaining therapy used in critical care settings to support patients experiencing severe cardiac or respiratory failure. By temporarily taking over the function of the heart and/or lungs, ECLS allows time for the underlying condition to be treated or for the organs to recover.
The process involves diverting blood outside the body to be oxygenated and cleared of carbon dioxide, then returning it to the patient’s circulatory system. Because of its complexity and risk, ECLS is typically reserved for patients in life-threatening situations where conventional therapies have been exhausted.
Respiratory therapists often play a crucial role in managing and monitoring ECLS, making it essential to have a solid understanding of its principles and applications. In this guide, you’ll find helpful explanations and targeted practice questions to deepen your knowledge and build confidence in handling this advanced therapy.
What is Extracorporeal Life Support?
Extracorporeal life support (ECLS) is an advanced life-saving technique used in critical care to support patients whose heart or lungs are unable to function adequately on their own. When traditional methods such as mechanical ventilation, medications, or oxygen therapy are no longer sufficient, ECLS can temporarily take over the work of these failing organs, giving the body time to recover.
The process involves removing the patient’s blood from the body and circulating it through an external machine where it is oxygenated, cleared of carbon dioxide, and then returned to the patient’s circulatory system. This external system essentially functions as an artificial heart and/or lung, depending on the type of ECLS being used.
Because it is such a resource-intensive and high-risk intervention, ECLS is typically reserved for patients in life-threatening situations—often as a last resort when conventional therapies have failed.
Types of Extracorporeal Life Support
- Extracorporeal Membrane Oxygenation (ECMO)
- Venoarterial (VA) ECMO
- Venovenous (VV) ECMO
- Extracorporeal CO2 Removal (ECCO2R)
Extracorporeal Membrane Oxygenation (ECMO)
ECMO is the most commonly known form of ECLS. It provides both oxygenation and carbon dioxide removal for patients suffering from severe respiratory or cardiac failure. The blood passes through a specialized membrane oxygenator, which serves as a substitute for the lungs and, in some cases, the heart.
This therapy is often initiated when conventional ventilation strategies, such as high PEEP or prone positioning, are insufficient. While it can be life-saving, ECMO carries significant risks, including bleeding, infection, and complications related to anticoagulation.
Respiratory therapists are often integral to the ECMO team, particularly in managing ventilator settings and monitoring gas exchange, although the scope of their involvement may vary by state or institution.
Venoarterial (VA) ECMO
VA ECMO supports both cardiac and respiratory function. In this mode, blood is withdrawn from the venous system, passed through an oxygenator, and then returned to the arterial system. This bypasses the heart and lungs entirely, making it ideal for patients with severe cardiac failure or cardiogenic shock.
Common indications for VA ECMO include:
- Cardiac arrest
- Cardiomyopathy
- Myocardial infarction with cardiogenic shock
- Failure to wean from cardiopulmonary bypass post-surgery
Note: Because it also supports hemodynamics, VA ECMO is more complex and requires close monitoring of cardiac output, perfusion pressures, and vascular resistance.
Venovenous (VV) ECMO
VV ECMO, in contrast, is used solely for respiratory support. Blood is extracted and returned through the venous system after being oxygenated and cleared of carbon dioxide externally.
It’s most commonly used for:
- Severe ARDS
- Viral or bacterial pneumonia
- Inhalation injuries
- COVID-19 related respiratory failure
Note: Unlike VA ECMO, VV ECMO does not provide circulatory support and is not appropriate for patients with cardiac failure. However, it’s less invasive than VA ECMO and often carries a lower risk profile when used appropriately.
Extracorporeal CO₂ Removal (ECCO₂R)
ECCO₂R is a more targeted and less invasive form of extracorporeal support designed specifically to remove carbon dioxide from the bloodstream. It is particularly useful in patients with hypercapnic respiratory failure, such as those with COPD or acute exacerbations, who are at risk of ventilator-induced lung injury from high pressures or volumes.
Unlike ECMO, ECCO₂R does not provide significant oxygenation support, but it enables clinicians to use lung-protective ventilator settings, reducing the risk of barotrauma and volutrauma. Its growing use in intensive care units represents a shift toward more nuanced, less invasive approaches to managing respiratory failure.
Extracorporeal Life Support Practice Questions
1. When is ECMO indicated?
It can be used for the management of severe, life-threatening respiratory failure or cardiogenic shock in patients who have not responded well to conventional types of treatment.
2. What are the three types of ECMO?
Venovenous, venoarterial, and arteriovenous
3. In hypoxic respiratory failure due to any cause, ECLS should be considered when?
It should be considered when the risk of mortality is greater than 50% and is indicated when the risk of mortality is greater than 80%.
4. A 50% mortality rate is associated with a P/F of what?
With a P/F of greater than 150 on an FiO2 of greater than 90%
5. An 80% mortality risk is associated with a P/F of what?
Less than 100 on an FiO2 of greater than 90%
6. ECMO is recommended for MLIS greater than what?
3
7. Gas flow in an ECMO circuit is referred to as what?
Sweep flow
8. The higher the sweep flow, the more?
The more CO2 is eliminated
9. Which form of ECMO involves a complete lung bypass?
Venoarterial ECMO
10. In order for venovenous ECMO to support oxygenation and CO2 removal, the patient must have what?
Adequate cardiac function
11. Patients with an acute lung injury and preserved cardiac function would be considered for which type of ECMO?
Venovenous ECMO
12. Which form of ECMO should be considered for patients with cardiogenic shock, with or without an acute lung injury?
Venoarterial ECMO
13. What form of ECMO is best indicated for patients with COPD and pre-lung transplant patients?
Arteriovenous EMCO
14. Which group has the best survival rate treated with ECMO?
Neonates with respiratory support
15. What is the key reason for making ECMO so successful in newborns?
Most clinical conditions treated with ECMO in newborns are reversible.
16. What are the different uses of ECMO?
It is mostly used for neonatal hypoxemic respiratory failure. Some examples of clinical conditions include PPHN, MAS, RDS, sepsis, and air leak syndrome.
17. Which of the following strategies is greatly responsible for decreasing the need for ECMO in neonates?
HFOV
18. Which condition is considered the 1st contraindication for neonatal ECMO?
Less than 2 kg of body weight
19. What are the suggested indications for pediatric ECMO?
PaO2/FiO2 greater than 75, oxygen index greater than 35, and a pre-ECMO pH less than 7.20
20. What are the cardiac applications of ECMO?
ECPR, CDH, fulminant myocarditis, and cardiomyopathy
21. What statement describes venoarterial ECMO?
A cannula is inserted into the right common carotid artery for arterial return
22. During the administration of venovenous ECMO, the therapist notices that the SvO2 is greater than the SaO2. What is the best explanation of this phenomenon?
The native cardiac output has increased
23. During venovenous ECMO, what effect does the cardiac output have on oxygenation?
Changes in cardiac output, either way, will have little influence on the patient’s oxygenation.
24. What are the major advantages of venovenous ECMO?
Cardiovascular support is not involved
25. What mechanisms affect the output of venovenous ECMO?
The size of the tubing, the rotations per minute, and the tension of the rollers
26. The therapist should evaluate raceway occlusion because too much roller tension could be associated with which of the following events?
Hemolysis
27. What is the advantage of having the centrifugal pump automatically respond to resistances against which it is pumping?
It maintains regulated flow through the system.
28. In the gas membrane exchanger, what is one of the limiting factors to the transfer the rate of oxygen across the membrane?
The thickness of the blood film between the membrane layers
29. Because the minimum flow rate required to remove condensation in the gas compartment usually results in excessive elimination of carbon dioxide, what should the respiratory therapist do?
Blend sweep gas with a carbogen mixture
30. What are the most common causes of a decrease in venous return in ECMO?
Hypovolemic state, malpositioning of the venous cannula, kinking of the cannula, and shifting of the mediastinum
31. It is not uncommon for patients undergoing ECMO to experience renal failure. What can be done to enhance renal function?
Perform hemofiltration
32. The ECMO specialist has noticed excessive clotting in the circuit despite increased doses of heparin. What is the most feasible explanation for this event?
Deficiency of ATIII
33. The respiratory therapist in charge of a patient on ECMO is monitoring the ACT every 30 minutes. The last ACT was 100 seconds. What should the therapist suggest at this time?
Increase the heparin dose
34. The respiratory therapist in charge of a patient on ECMO has noticed an increase in pre-membrane pressures. What is the most probable explanation?
Clotting in the circuit
35. How can membrane malfunction be suspected?
Narrowing of the pre-membrane and post-membrane PaCO2
36. What ventilator settings are typically used in ECMO for respiratory support?
A tidal volume of 5-7 ml/kg, PIP 25-25 cmH2O, and a frequency 10-12.
37. What ECMO flow is considered as minimal support?
30 mL/Kg
38. What is considered the most concerning complication of ECMO in a newborn?
Intracranial hemorrhage
39. What are the main uses of ECMO?
Neonatal Hypoxemic Respiratory Failure, i.e. Persistent pulmonary HTN of the newborn (PPHN), Meconium aspiration syndrome (MAS), Respiratory distress syndrome (RDS), sepsis, and air leak syndromes
40. What are the uses of ECMO for cardiac applications?
Congenital heart disease, fulminant myocarditis or cardiomyopathy, and extracorporeal cardiopulmonary resuscitation (ECPR)
41. What needs to be monitored in the circuit function?
Water temperature, venous saturation, circuit integrity, pre- and post-membrane blood gases, air bubbles, hemodynamics, organ perfusion, lab tests, and a neurologic assessment
42. When can ECMO be used in neonates?
ECMO can be used at greater than 32 weeks gestation with no intraventricular hemorrhage.
43. What are the cardiac applications for ECMO?
Congenital heart disease, myocarditis or cardiomyopathy, and extracorporeal cardiopulmonary resuscitation (ECPR)
44. How much of the cardiac output is supported by ECMO?
80%
45. What is used for anticoagulation?
Heparin
46. What is the main goal of ECMO?
The main goal is to discharge the patient without any disability.
47. What is the survival rate for ECMO?
Greater than 65% in infants
48. What is the most common mechanical complication that can occur during ECMO?
Clot formation
49. How can you wean a patient from ECMO?
Weaning occurs by gradually turning down the pump flow in VA or by turning down the sweep flow in VV.
50. During venoarterial ECMO, how is blood returned to the patient’s body?
It is returned to the body via arterial circulation.
51. What is the primary purpose of the sweep gas in an ECMO circuit?
To facilitate the removal of carbon dioxide from the blood.
52. Which type of ECMO provides both respiratory and hemodynamic support?
Venoarterial ECMO.
53. What lab test is commonly monitored to assess anticoagulation during ECMO?
Activated clotting time (ACT).
54. What is a common cannulation site for venovenous ECMO?
Right internal jugular vein.
55. Why is temperature regulation important during ECMO?
Hypothermia can impair coagulation and metabolic processes.
56. What is the primary indication for ECMO in pediatric patients?
Severe respiratory failure unresponsive to conventional therapies.
57. What is the main function of the membrane oxygenator in ECMO?
Gas exchange—adding oxygen and removing carbon dioxide.
58. What is the role of the blender in the sweep gas system?
It adjusts the oxygen concentration delivered to the oxygenator.
59. What are the signs of hemolysis in a patient on ECMO?
Dark urine, elevated plasma-free hemoglobin, and jaundice.
60. What should be done if a clot is suspected in the ECMO circuit?
Inspect the circuit, notify the ECMO team, and possibly replace the component.
61. What does increasing the sweep gas flow rate do?
It enhances carbon dioxide removal.
62. Which patients are poor candidates for ECMO due to irreversible conditions?
Those with terminal illness or irreversible brain damage.
63. Why must ECMO patients be monitored closely for bleeding?
Because systemic anticoagulation increases hemorrhage risk.
64. What imaging study may be needed to confirm cannula placement?
Chest X-ray or ultrasound.
65. What is the significance of monitoring pre- and post-oxygenator pressures?
To detect clots or malfunction in the oxygenator.
66. How does ECMO help reduce ventilator-induced lung injury?
By allowing lung rest with lower ventilator settings.
67. What neurologic complication is most feared during ECMO?
Intracranial hemorrhage.
68. What does a decreasing post-oxygenator PaO₂ indicate?
Oxygenator failure or malfunction.
69. Which setting is adjusted first when titrating oxygenation in ECMO?
Blood flow rate.
70. What clinical parameter indicates effective ECMO support?
Improved oxygenation and perfusion markers like lactate and urine output.
71. What must be ensured before starting ECMO in an emergency?
Cannulation supplies, experienced personnel, and a functioning circuit.
72. Why is air embolism a risk in ECMO?
The system operates under negative pressure on the venous side.
73. What can a sudden drop in ECMO blood flow indicate?
Cannula dislodgment or kinking.
74. What electrolyte disturbances are common in ECMO patients?
Hypokalemia and hypocalcemia.
75. What role does the heater-cooler unit play in ECMO?
It regulates blood temperature before returning it to the patient.
76. What is the most common vascular access site for arterial cannulation in VA ECMO?
The right common carotid artery.
77. Why is anticoagulation necessary during ECMO?
To prevent clot formation within the extracorporeal circuit.
78. What does the term “lung rest” mean in ECMO?
Using minimal ventilator settings to prevent further lung injury while ECMO supports oxygenation.
79. What blood test is used to monitor oxygenation during ECMO?
Post-oxygenator PaO2 measurement.
80. How does the ECMO circuit simulate cardiopulmonary function?
It bypasses the heart and/or lungs to oxygenate blood and remove carbon dioxide.
81. What is the typical ACT target range for anticoagulation during ECMO?
180 to 220 seconds.
82. What does a rising pre-oxygenator pressure suggest?
Clot formation or resistance before the oxygenator.
83. What is a potential sign of poor venous drainage in ECMO?
Decreased circuit flow and increased negative pressure alarms.
84. What’s the significance of venous saturation in ECMO monitoring?
It reflects the balance between oxygen delivery and consumption.
85. What is the risk of cannulating the femoral artery in adults?
Limb ischemia.
86. Which anticoagulant is most commonly used in ECMO circuits?
Unfractionated heparin.
87. What is an ECMO bridge to transplant?
Using ECMO support while awaiting lung or heart transplantation.
88. What parameter would best indicate systemic perfusion in ECMO?
Serum lactate level.
89. What is the function of the bubble detector in an ECMO circuit?
To detect and prevent air embolism.
90. Why is dual-lumen cannulation preferred in some VV ECMO setups?
It allows both drainage and return through one vessel, often the internal jugular vein.
91. What is a major concern when decannulating a patient from ECMO?
Bleeding at the cannulation site.
92. What is a typical complication of prolonged ECMO support?
Infection and thrombocytopenia.
93. Why are platelet counts monitored closely in ECMO?
Low platelets increase bleeding risk, while high levels may signal clotting risk.
94. What could a sudden drop in oxygen saturation during ECMO indicate?
Cannula dislodgement, oxygenator failure, or increased patient demand.
95. What is the impact of excessive hemolysis in ECMO patients?
It can lead to renal damage and jaundice.
96. How is renal support often integrated with ECMO?
By connecting continuous renal replacement therapy (CRRT) to the ECMO circuit.
97. What role does echocardiography play in ECMO?
It helps assess heart function and cannula placement.
98. What is recirculation in ECMO?
Oxygenated blood returns directly to the drainage cannula instead of the patient.
99. What condition may require conversion from VV to VA ECMO?
New onset or worsening cardiac failure.
100. What type of oxygenator is commonly used in modern ECMO systems?
Microporous hollow fiber membrane oxygenators.
Final Thoughts
Extracorporeal life support represents one of the most advanced and critical interventions available in modern medicine, offering a lifeline to patients whose hearts or lungs can no longer function on their own.
Whether it’s ECMO or ECCO₂R, each form of ECLS requires a deep understanding of physiology, technology, and patient care. As a respiratory therapist, your role in this process is both vital and impactful.
By mastering the concepts covered in this guide and testing your knowledge with practice questions, you’re taking an important step toward providing exceptional care in the most challenging clinical scenarios.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Rrt, Des Terry Jardins MEd, and Burton George Md Facp Fccp Faarc. Clinical Manifestations and Assessment of Respiratory Disease. 8th ed., Mosby, 2019.
- Swol, Justyna. “Indications and Outcomes of Extracorporeal Life Support in Trauma Patients.” PubMed, June 2018.
- “Extracorporeal Life Support in Critically Ill Adults.” National Center for Biotechnology Information, U.S. National Library of Medicine, 1 Sept. 2014.
- “Extracorporeal Life Support for Severe Acute Respiratory Distress Syndrome in Adults.” National Center for Biotechnology Information, U.S. National Library of Medicine, Oct. 2004.