The impact of orthostatic challenge on arteriovenous hemodynamics and volume changes of the lower extremity.

Objective: To assess the impact of an orthostatic challenge on arterial and venous hemodynamics and its relation to lower leg volume.

Methods: Hemodynamic parameters of 18 healthy subjects (six men; mean age, 38 ± 11 years) were assessed in the left proximal superficial femoral artery and femoral vein in supine position and during a 10-minute orthostatic challenge using duplex sonography. Lower leg volume was measured using an optoelectronic device.

Results: During orthostatic challenge, vein diameter increased significantly while artery diameter decreased compared with the supine position (P < .01 for both). Arterial and venous blood flow in the supine (baseline) position was similar (P = .54). During the first 2 minutes of orthostatic challenge, both arterial and venous blood flow significantly decreased, with a more important decrease in venous blood flow (P < .01 compared with artery). Following this nadir, venous blood flow increased above baseline levels, followed by a plateau flow similar to baseline. Arterial flow returned to flow level inferior to baseline values (P < .05). Lower leg volume increased from 2348 ± 399 mL to 2423 ± 433 (P < .001) within the first 5 minutes with no further increase thereafter.

Conclusions: A 10-minute orthostatic challenge has a marked impact on both arterial and venous hemodynamics with a multiphasic change of venous and arterial flow. Lower leg volume increase correlates with venous and arterial flow response. These findings help to better understand the role of gravitational force in various vascular diseases of the lower extremities.