<正>Objective: To study the effect of CO2 pneumoperitoneum and the special 30 degree head-down tilt position on the venous hemodynamics in the lower extremity. Methods: Color doplex ultrasound was adopted to evaluate the diameter and blood flow velocity of the right femoral vein of 18 patients undergoing gynecologic laparoscopy under the same pressure of pneumoperitoneum of 12 mmHg. The diameter of femoral vein and the flow velocity were measured; the blood flow volume was calculated based on the equation of Q = vπr2 . Result: After establishment of pneumoperitoneum

the dilation of the femoral vein and the decrease in the velocity and volume can be observed （P < 0.05）. And the 30 degree head-down position could increase the flow velocity and volume of the femoral vein and decrease the diameter of the vessel （ P < 0.05）. At 30 minutes of the 30 degree head-down tilt position

the blood flow ameliorated compared with that in prone position after the establishment of pneumoperitoneum. After deflation of pneum