Duplex ultrasound assessment of venous diameters, peak velocities, and flow patterns.

Duplex ultrasound was used to study the diameters, flow patterns, and peak blood flow velocities of the common femoral vein (CFV) in 12 normal subjects (mean age 35 years). Each subject was supine and non-weight-bearing on a tilt table and rotated in 10-degree increments from -10 degrees (head down) to +30 degrees (head up). Cross-sectional B-mode image was used to monitor continuously CFV diameter for 5 minutes in each position. Doppler flow patterns were recorded in longitudinal axis; heart rate and respiratory movements were also noted. CFV flow was affected by respiratory and cardiac events. At -10 degrees flow was primarily related to cardiac events, with flow increasing during diastole. At +30 degrees flow varied minimally with the cardiac cycle and was primarily respiration dependent, stopping at peak inspiration. Proceeding from -10 to +30 degrees the mean maximal CFV diameter corrected for body surface area increased 92% (0.47 +/- 0.11 cm/m2 to 0.90 +/- 0.16 cm/m2, p less than 0.001), whereas peak flow velocity decreased from 41 +/- 10 cm/sec to 13 +/- 5 cm/sec, p less than 0.001. There was a linear, inverse relationship between mean peak velocity and mean corrected diameter, r = -0.99. The study confirms the multiple influences on venous flow patterns and establishes a quantitative relationship between venous diameters and flow velocities.