Effect of different position and CO(2) pneumoperitoneum on deep vein hemodynamics of lower limb / 中华胃肠外科杂志

<p><b>OBJECTIVE</b>To study the effect of laparoscopic surgery position and CO(2) pneumoperitoneum on deep vein hemodynamics of lower limb.</p><p><b>METHODS</b>Color Doppler ultrasound was adopted to evaluate the diameter, blood velocity and the amount of the blood flow in the lower extremity of 37 gastric cancer patients undergone laparoscopic surgery from November 2007 to August 2008 in our hospital. Three kinds of position(prostration, head-down tilt position and feet-down tilt position) before the establishment of pneumoperitoneum and three different pressure of CO(2) pneumoperitoneum( 8 mm Hg, 12 mm Hg, 16 mm Hg ) after the establishment of pneumoperitoneum were applied during laparoscopic surgery.</p><p><b>RESULTS</b>Compared with the stage of prostration before the pneumoperitoneum, the femoral vein diameter decreased (P<0.05), the velocity and the amount of blood flow increased (P<0.01, P<0.05) in head-down tilt position; the femoral vein diameter increased(P<0.01), the velocity and the amount of blood flow decreased(P<0.01, P<0.05) in feet-down tilt position or the establishment of pneumoperitoneum. Furthermore, with the increase of pneumoperitoneum pressure, the femoral vein diameter increased, the velocity and the amount of blood flow decreased(P<0.05).</p><p><b>CONCLUSIONS</b>The head-down tilt position is conducive for the blood to recirculate, which will degrade the risk of deep vein thrombosis after the laparoscopy. The feet-down tilt position and CO(2) pneumoperitoneum can interfere the recirculation of blood, and increase the risk of deep vein thrombosis after the laparoscopy.</p>

Three-dimensional simulation of pulsatile blood flow in human thoracic aorta / 第二军医大学学报

Objective: To study the distributions of velocity, wall pressure and wall shear stress of blood flow in the human thoracic aorta under normal physiological pulsatile flow conditions, so as to provide a theoretical foundation for elucidating the pathogenesis of aortic dissection. Methods: By virtue of the Computational Fluid Dynamics and the fundamentals of hemodynamics, the authors obtained the numerical simulations and flow visualizations of pulsating blood flow in the human thoraric aorta. Results: The distributions of velocity, wall pressure, wall shear stress and path line of the blood flow in the thoracic aorta were calculated with a function of time in the cardiac circle. The systoltic wall pressure and its dp/dt were higher than diastolic wall pressure and its dp/dt. The pressure of lateral wall was higher than the pressure of medial wall during systole. A distinct depressed pressure was found located at the intersection between aortic arch and descending aorta. Shear stress of wall of lateral aortic arch was less than that of medial wall of aortic arch and the shear stress change in medial wall of aortic arch was greater than that in the lateral aortic wall. The shear stress was in a cyclic and alternative manner. Conclusion: The findings suggest that the wall pressure may be related to the development of aortic dissection.