Techniques for Partial Extracorporeal Support
Depending on the range of operative blood flows and cannula configurations, techniques may be classified as follows:
1. VV-ECCO2R. This is the classical ECCO2R techniques as proposed by Gattinoni [39]. A standard adult ECMO system runs with ECBF ranging from 1.5 to 2.5 L/ min. With modern technology, it is possible to use low-medium surface oxygenators with small-size tubes and cannulas that provide ECBF ranges from 500 mL/ min up to 2-2.5 L/min.
- 2. Low flow ECCO2R (LF-ECCO2R). Various devices have been recently implemented to specifically provide CO2 removal operating with very low extracorporeal blood flow, ranging from 250 to 500 mL/min [121, 129-132]. Depending on the level of CO2 content in the venous blood, these systems allow removal of up to about 80-120 mL of CO2/min. Most of these systems can be employed with double-lumen catheters similar to those used for continuous renal replacement techniques (size 14-17 Fr).
- 3. Arteriovenous CO2 removal (AVCO2R). Femoral vein and artery are both can- nulated with percutaneous approach. The oxygenators (Novalung®) offer extremely low resistance to blood flow (surface area 1.3 m2), which is driven by patient’s arteriovenous pressure gradient. Effective blood flow is conditioned by the size of arterial cannula (13-15-17Fr) and by mean systemic pressure, ranging from 0.6 to 1.8 L/min [133]. No heat exchanger is provided. This technique can be associated with bleeding and limb ischaemia due to cannulation of the femoral artery [134, 135].
