I'm not a Doctor, but I play one on the internet. LoLoLoLo
When your limbs "go to sleep" and tingle, it means that pressure is being applied and putting the squeeze on nerve pathways and blood vessels, so the nerves can't transmit signals properly, and the blood vessels can't bring oxygen and nutrients to the nerves.
So, it could be that your throne is to high or that your are situated too far back on the throne, which would be a way for blood to get restricted to your feet. Of course, your blood pressure may be the culprit, as well.
kdg