In vivo measurements of collapse behavior of human internal jugular vein during head-up tilt tests.

Objective: Human internal jugular veins (IJVs) can collapse during posture change from supine to erect, which might influence intracranial hemodynamics. This study aims to quantitatively describe the gradual collapse behavior of human IJVs during head-up tilt tests from supine to erect.

Approach: Ten male and ten female subjects were enrolled in head-up tilt tests. Ultrasound screening was performed on the right IJV at five equidistant points between its junction with the subclavian vein and the location of the bifurcation of the arteria carotis communis, with the body at 0°, +10°, +20°, +30°, 40°, +50°, +60°, +70°, +80°, and  +90°. Geometrical models were reconstructed and lumen areas were statistically analyzed based on extracted outlines of venous lumen.

Main Results: The right IJV lumen area reduced significantly when tilt angle was increased from 0° to 20°, as the normalized lumen areas reduced to about 0.5 at the lowest point and about 0.2 at the others. The mean normalized lumen areas of the middle point were much smaller, which dropped below 0.1 when the tilt angle was larger than 40°.

Significance: Collapse behavior of human right IJVs was quantitatively described by obtaining variations of lumen outlines and areas at different locations and tilt angles. Reconstructed geometrical models could be used to gain nonlinear pressure-volume relations and inner blood flow characteristics, which can benefit research on human cerebral venous outflow.