A Vishnu Mudra is alternate nostril breathing, closing off one nostril as you breath in through the other. Then you close off the other and breath through the nostril.

Here's a couple of links.

http://sacred-earth.typepad.com/yoga...pranayama.html


http://www.expandinglight.org/ananda...shnu-mudra.php

I don't mean to imply you have a blockage, it was just the oxygenated blood from one nostril and the de- oxygenated blood from the other that got me thinking in that direction.
I realy don't know much on this , just what I read but I think this may be done before you start your throat friction meditation. ( 3-5 minutes)
Maybe someone here with better knowledge can add something.