ECMO system configuration

ECMO Fig_cropped.jpg

Extracorporeal life support (ECLS) is an artificial means of maintaining adequate oxygenation and carbon dioxide elimination to enable injured lungs to recover from underlying disease. Technological advances have made ECLS devices smaller, less invasive, and easier to use. ECLS, particularly venovenous extracorporeal mem- brane oxygenation (ECMO), has been used as rescue therapy in patients with severe acute respiratory distress syndrome and refractory hypoxaemia.

The ultimate goal of ECLS is to maintain adequate oxygen delivery and CO2 elimination to partly or completely unload the cardiopulmonary system and enable recovery from underlying disease. During ECLS, a pump drives blood flow through the extracorporeal circuit, which includes an oxygenator (eg, hollow-fibre polymethylpentene). The blood interacts with a constant flow of oxygen (sweep-gas flow) across the hollow fibres, which enables gas exchange to take place. Extracorporeal oxygenation and CO2 removal are controlled by three features: extracorporeal blood-flow rate, which depends on many different factors, but is controlled mainly by modification of the centrifugal-pump speed; sweep-gas flow rate, which is controlled by a flow meter; and fraction of delivered oxygen in the sweep gas, which is controlled by a gas blender. Alteration of these features achieves different outcomes.

In our lab a series of studies using ECMO in veno-venous configuration are being done specially for severe acute respiratory distress syndrome (ARDS) in association with different strategies of mechanical ventilation to optimize and develop new approach to this critical ill patient.

  • Extracorporeal life support (ECLS) is not a treatment, but an artificial means of providing oxygenation and elimination of carbon dioxide (CO2) to enable recovery from and treatment of underlying lung disease

  • Technological advances have led to reduced-size ECLS devices that are less invasive and easier to use than previous devices, and which might represent an important step towards improved management and outcome of patients with acute respiratory distress syndrome (ARDS)

  • ECLS can be used in patients with ARDS in two distinct settings: for rescue from the harmful effect of refractory hypoxaemia, hypercapnia, or both; and for rescue from or prevention of injurious levels of mechanical ventilation

  • Extracorporeal CO2 removal, a less invasive and simpler ECLS configuration, might minimise ventilator-induced lung injury in patients with ARDS, but confirmatory clinical trials are needed

  • Rigorous evidence regarding the optimum timing, selection of patients, and indications for ECLS in severe ARDS, and its ability to improve patients’ short-term and long-term outcomes are needed before widespread adoption of this therapy