The effect of a simulated manipulation position on internal carotid and vertebral artery blood flow in healthy individuals.

The simulated manipulation position is one of several premanipulative screening tests recommended to assist in identifying patients at risk of complications from high velocity thrust manipulation of the cervical spine. The effects of this position on blood flow in the vertebral artery has been measured, but not in the internal carotid artery. Fourteen healthy subjects participated in a pre-test post-test single group study to determine the effect of a simulated manipulation position on blood flow in both the internal carotid and vertebral arteries. Duplex ultrasound with colour Doppler imaging was used to image the internal carotid and vertebral arteries and to measure blood flow velocity with the neck in neutral and simulated manipulation positions. A measure of distal vascular resistance, the resistance index, was calculated. There was a significant (p<0.05) reduction in the resistance index in the vertebral arteries ipsilateral to the rotation component of the simulated manipulation position. Placing the cervical spine in a simulated manipulation position, did not adversely affect blood flow through the internal carotid and vertebral arteries. Further research is needed to determine how the simulated manipulation position affects internal carotid and vertebral artery blood flow in individuals who have signs or symptoms of neurovascular insufficiency.