Experimental design for testing oxygen delivery to perfused kidneys. (A) Higher arterial blood flow increases oxygen delivery to the kidney (O2 supply). This also increases glomerular filtration and hence tubular reabsorption (O2 demand). In a perfusion-limited scenario, O2 supply and demand should be matched and a linear relationship is expected between arterial oxygen flow and renal respiration. Otherwise, if oxygen exchange from blood to the kidney was diffusion-limited, then the relationship between arterial oxygen flow and renal respiration is expected to tail off. Thus, it is possible to test for diffusion-limited oxygen exchange by relating measurements of renal respiration with arterial oxygen flow. (B) Image of machine for normothermic kidney perfusion and schematic diagram of the circuit in the kidney perfusion machine: 1, kidney; 2, organ containing with perforated kidney sling; 3, arterial cannula at kidney inlet; 4, venous cannula at kidney outlet; 5, ureter outlet duct; 6, urine flow meter; 7, duct for recirculation of fluids leaked by the kidney; 8, soft-shell reservoir; 9, centrifugal perfusion pump; 10, oxygenator and heat exchanger; 11, heat exchanger water inlet; 12, heat exchanger water outlet; 13, oxygenator has inlet; 14, in-line blood gas analysis sensor; 15, arterial flow meter; 16, arterial pressure sensor; and 17, infusion or syringe pump.
