Extracorporeal life support (ECLS) serves as an advanced medical therapy designed to offer cardiac and respiratory support for patients struggling with organ failure.
In this treatment, blood is externally circulated through a machine for oxygenation before reintroducing it into the patient’s body.
Given its critical nature, ECLS is generally reserved for life-threatening conditions when conventional treatments have failed.
As respiratory therapists often play a key role in administering ECLS, this guide aims to facilitate a deeper understanding of the subject.
Here, we offer practice questions and valuable insights to make your learning journey smoother.
What is Extracorporeal Life Support?
Extracorporeal life support is a specialized treatment that assists patients who are unable to maintain adequate gas exchange or perfusion through their own organs.
The therapy involves diverting the patient’s blood to an external machine, where it is oxygenated and then returned to the body’s circulatory system.
ECLS is a high-level intervention utilized only in dire, life-threatening situations where traditional methods have proven ineffective.
Types of Extracorporeal Life Support
- Extracorporeal Membrane Oxygenation (ECMO)
- Venoarterial (VA) ECMO
- Venovenous (VV) ECMO
- Extracorporeal CO2 Removal (ECCO2R)
Extracorporeal Membrane Oxygenation (ECMO)
ECMO serves as a subset of ECLS, specifically designed for gas exchange—oxygenation and carbon dioxide removal.
This technique is used for managing severe respiratory or cardiac conditions that have not responded to conventional treatments.
Respiratory therapists are frequently involved in ECMO therapy, although regulations on their involvement may vary by state.
Venoarterial Extracorporeal Membrane Oxygenation (VA ECMO)
VA ECMO is a form of ECLS where blood is drained from the patient’s venous system and circulated through a machine for oxygenation.
The oxygen-rich blood is then returned to the body via the arterial system.
This approach is generally used to treat patients experiencing cardiovascular failure, offering hemodynamic support. It is most commonly indicated in cases of cardiogenic shock.
Venovenous Extracorporeal Membrane Oxygenation (VV ECMO)
VV ECMO is another form of ECLS that focuses on treating acute respiratory failure caused by conditions like viral or bacterial pneumonia.
Similar to VA ECMO, blood is drained from the venous system, oxygenated externally, and returned via the venous system.
However, unlike VA ECMO, VV ECMO does not provide hemodynamic support.
Extracorporeal CO2 Removal (ECCO2R)
ECCO2R is a specialized form of ECLS focused on removing carbon dioxide from the blood. It is generally less invasive than ECMO and is primarily used in cases of hypercapnic respiratory failure, where the body can’t expel CO2 effectively.
Unlike full-fledged ECMO, ECCO2R typically doesn’t provide comprehensive oxygenation, but it allows for safer, lower ventilator settings.
Its role in critical care is growing, offering an alternative or adjunct to more aggressive forms of extracorporeal life support.
Note: By familiarizing yourself with these different types of Extracorporeal Life Support, you’ll be better equipped to manage life-threatening situations. Now that you’re ready, let’s delve into the practice questions to further enhance your understanding.
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.
Final Thoughts
Extracorporeal life support serves as a critical medical intervention designed for life-threatening scenarios where conventional therapies have fallen short.
As a respiratory therapist, understanding the intricacies of various ECLS modalities is essential for optimal patient care.
This guide has aimed to deepen your understanding of these complex yet invaluable treatment options.
By familiarizing yourself with the underlying principles and specific types of ECLS, you are better prepared to contribute effectively to a multidisciplinary team focused on saving lives in critical care settings.
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
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- 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.