A device for applying pressure to one or more neck veins of a subject comprising: a circumferential collar (10) sized to encircle the neck of a subject； and one or more inwardly directed protuberances (20, 40) integral to the collar； wherein the protuberances are located on the collar such that they are disposed above one or more neck veins of the subject when the collar is encircling the neck of the subject and exert a pressure on said one or more neck veins equivalent to a fluid pressure within the range of 5 mmHg to about 50 mmHg and restrict blood flow egressing from the head of the subject.
