Pressure Drop, Shear Stress, and Activation of Leukocytes During Cardiopulmonary Bypass: A Comparison Between Hollow Fiber and Flat Sheet Membrane Oxygenators

Abstract

The membrane oxygenator is known to be superior to the bubble oxygenator, but little information is available about the difference between the hollow fiber and flat sheet membrane oxygenators with regard to pressure drop, shear stress, and leukocyte activation. In this study, we compared these 2 types of membrane oxygenators in patients undergoing cardiopulmonary bypass (CPB) surgery with special focus on leukocyte activation and pressure drop across the oxygenators. Plasma concentration of elastase, a marker indicating leukocyte activation, increased to 593+/-68% in the flat sheet oxygenator group versus 197+/-42% in the hollow fiber oxygenator group (p<0.01) at the end of CPB compared to their respective baseline concentrations before CPB. Pressure drop across the oxygenator was significantly higher in the flat sheet group than in the hollow fiber group throughout the entire period of CPB (p<0.01). High pressure drop across the oxygenator as well as the calculated shear stress was positively correlated with the release of elastase at the end of CPB (r = 0.760, p<0.01, r = 0.692, p<0.01). However, this positive correlation existed in the flat sheet oxygenator but not in the hollow fiber oxygenator. Clinically, both membrane oxygenators have satisfactory performance in O2 and CO2 transfer. These results suggest that a higher pressure drop across the flat sheet oxygenator is associated with more pronounced activation of leukocytes in patients undergoing cardiopulmonary bypass.

Real-Time Intravascular Shear Stress in the Rabbit Abdominal Aorta

“…Identification of arterial regions of low wall shear stress (WSS) would predict progression of atherosclerosis [10], localization of high-risk coronary atherosclerotic plaques, vessel wall remodeling [11], and abdominal aortic aneurysm (AAA) [12], [13]. Furthermore, identification of specific regions in the prosthetic valve leaflets [14], the cardiopulmonary bypass machine [15], and left ventricular assist device (LVAD) would predict thrombus formation [16]. In this context, the ability to measure real-time shear stress would advance the field of cardiovascular research.…”

Comparison of hollow-fiber membrane oxygenators with different perfusion modes during normothermic and hypothermic CPB in a simulated neonatal model

“…11 The oxygenator with a lower pressure drop resulted in less leukocyte activation. 11 The pressure drops of the membrane oxygenators during CPB in pediatric patients are important because of the very high flow rates used, particularly in neonates and infants. The pump flow rates are usually maintained at 150 Á 200 mL/ kg/minute in neonates and infants compared to only 50 mL/kg/minute in adult CPB cases.…”

Computational Model of Device-Induced Thrombosis and Thromboembolism

“…For example, in the native circulatory system, shear stresses range from 20 to 60 dynes cm −2 (calculated from data from Fung 16 ). In hollow-fiber hemodialyzers, shear stresses have been estimated 9,37 in the range of 15-25 dynes cm −2 , while oxygenator values are estimated 8,24 in the range 20-130 dynes cm −2 . The wall shear stresses in our flow cells were 20 and 174 dynes cm −2 in the large and small tubing, respectively (Table 4).…”