Internal jugular vein blood flow in the upright position during external compression and increased central venous pressure: an ultrasound study in healthy volunteers.

BACKGROUND

External compression of the jugular veins is an effective method to increase intracranial blood volume and brain stiffness in rats and healthy volunteers. It has been reported that, on assuming an upright posture, cerebral venous drainage is distributed away from the internal jugular veins (IJVs) to the cervical venous plexus, causing complete collapse of the IJV. If so, it is not clear why external IJV compression would increase intracranial blood volume, but the latter is frequently observed in neurosurgery in the sitting position. The aim of this study was to observe the effect of external IJV compression and the Valsalva maneuver on the change in IJV cross-sectional area and IJV flow in volunteers in the upright posture.

METHODS

After Research Ethics Board approval, we used ultrasound to evaluate both IJV cross-sectional areas and peak velocities in ten healthy volunteers in the sitting position. With the volunteers breathing normally at rest, we applied the Valsalva maneuver along with circumferential supraclavicular compression of 15 mmHg. Imaging was performed at the level of the cricoid cartilage and at the most superior level under the mandible. The IJV flow was calculated using the product of Doppler velocity and IJV cross-sectional area.

RESULTS

Flow was detected in both IJVs of all subjects. The median [interquartile range] cross-sectional area for the right IJV at the level of the cricoid was 0.04 [0.03-0.08] cm (baseline), with collar 0.4 [0.2-0.6] cm (P = 0.003 compared with baseline). There were no significant changes in the median blood flow.

CONCLUSIONS

Compression of the internal jugular veins or an increase in intrathoracic pressure does not reduce venous drainage but actually may increase intracranial venous volume.