What is ECMO?
Extracorporeal membrane oxygenation (ECMO) is a procedure of prolonged artificial blood circulation and oxygen saturation (oxygenation) in the blood, performed outside the body (extracorporeally), which is used in patients with acutely developed and potentially reversible respiratory and/or cardiac failure, whose treatment does not respond to the maximum standard therapy. For blood pumping (artificial blood circulation) the equipment similar to the heart-lung machine, which is applied in cardiac surgery, is used. The connection of the tube system of the equipment to the body is initiated by placing the tubes in large arteries and veins, or directly in cardiac chambers.
For patients with heavy respiratory failure the diagram of connection to the ECMO cir-cuit is illustrated in the Figure below. These patients solely require considerable oxygen saturation in the blood, and do not need to maintain cardiac pump function. Therefore, for this category of patients the so-called veno-venous ECMO is sufficient, where oxygen saturation in the blood takes place in the venous part of the blood circulatory system of the body. Oxygen-rich blood is then carried through the body by the heart. The main advantage of veno-venous ECMO lies in its ability to provide the «guarding» mode for lungs in the course of normalization/restoration of their function. Traditionally, patients with lung injuries require an artificial lung ventilation (ALV). The ALV device pumps up the oxygen as part of an airway into the patient's lungs. If lungs are badly injured, in order to maintain the normal level of oxygen in the blood, the high pressure of the given gas mixture and the concentration of oxygen in it are required. This, in turn, leads to the traumatizing of lungs tissues to a greater extent and indicates the need to increase the pressure and the concentration of oxygen in the air mix, which is provided by the ALV device. Thus, the vicious circle of the injury of «sore» lungs is closed. ECMO «breaks» this vicious circle allowing lungs to be restored in an «attenuated" mode of ventilation, and an organism to cope with the main disease. This process can be compared to that of a plaster bandage providing «rest» to a hand with a broken bone. Therefore it is necessary to remember that ECMO is not a treatment method, but a way to provide a «bridge» to recovery.
Figure – The diagram of veno-venous ECMO
In case of need to maintain the work of the heart, ECMO is connected according to the di-agram of veno-arterial blood circulation. With that oxygen-poor blood is pumped up by the pomp (pump) through an artificial lung (oxygenator) into the arterial canal.
Figure – The diagram of veno- arterial ECMO