Arch Surg Chicago
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Venous valves will close when the reversal of the normal pressure gradient generates a sufficient reverse flow velocity. By testing 20 healthy subjects with ultrasonic duplex scanning and controlled limb compression. It was found that the velocity of reflux is related to the external compression pressure. ⋯ The reflux velocities in response to a Valsalva maneuver are progressively lower in more distal veins--the profunda femoris, the superficial femoral vein, and the popliteal vein. With reverse velocities lower than 30 cm/s, the valves will not close and reflux can persist. Valsalva's maneuver only allows a diagnosis of valvular competence at the most proximal level in the venous tree.