If this is, indeed, an issue of blood circulating to the head, you will feel some improvement very quickly, if you are able to relax in this position and keep your mind clear of any thoughts. Just breathe. Direct the blood to the head.
If you want, you can put a roll or pillow under your ankles and if your arms want to change at some point, you can put them straight out in front of you for a bit.
One thing good about this posture is that you can do it for as long as you want.