Platelet and leukocyte activation and design consequences for thoracic artificial lungs

Blood contact with the prosthetic surfaces of artificial lungs causes extensive activation of molecular and cellular mediators of coagulation and inflammation that can lead to patient morbidity and mortality. To determine the effects of artificial lung fiber bundle shear stress and surface area on blood activation, porcine blood was recirculated for 4 hours through circuits containing mock artificial lungs with bundle shear stresses of 11.6, 7.3, and 3.9 dynes/cm² and surface areas of 5.2, 3.5, and 1.7 cm²/ml of circuit volume. Blood from these circuits was assayed for platelet and leukocyte counts, soluble P-selectin concentrations, and lactoferrin concentrations to determine the level of platelet and leukocyte adherence to the circuit, platelet activation, and leukocyte activation, respectively. Neither platelet nor leukocyte counts were significantly affected by shear stress or surface area. P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle shear stress of 11.6 dynes/ cm². P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle surface area of 5.2 cm²/ml of circuit volume. Artificial lungs, therefore, should be designed with average bundle shear stresses < 11.6 dynes/cm² and with surface areas < 5.2 cm²/ml of circuit volume. Current thoracic artificial lungs meet both these requirements.