Figure 2.

Principles of bubble and surface oxygenation during hypothermic kidney machine perfusion. (A) During the entire wash phase, the perfusion fluid is uploaded with oxygen by bubble oxygenation realized by insufflating the carbogen directly to the perfusion solution in the reservoir via a submerged perforated O₂ tubing segment (1). The perfusion fluid enters the reservoir by a separate wash line (2) and by creating waves the efficiency of this O₂ uploading process increases (3). (B) Surface oxygenation was given at 200 mL/min during kidney perfusion via arterial cannulation with a mean perfusion pressure of 30 mm Hg (4) (and closure of the wash line (5) and removal of the submerged tubing segment of the Luer lock (6)). (C) The efficiency of surface oxygenation is enhanced during regularly scheduled wash cycles (7), resulting in breaking the perfusate’s surface layer (8) and increasing the oxygen diffusion in the perfusion fluid. Figure and figure legend slightly adapted but based on Figure 1 of T. Darius et al. [16].