Before you do anything I would see a doctor and make sure that your circulation problems aren't related to any underlying conditions such as blocked arteries or veins, or retention of fluid in your lower extremities. Others have offered good advice. I have only recently begun to meditate again on cushions. I, too, have circulation problems. For this reason, after years of sitting in half-lotus, ill health has made that impossible. I am sitting in traditional cross-legged style, no lotuses anymore and I change positions whenever it feels like pressure, pain, or numbness is occurring. I have a stent in my left groin area and a bypass near my left ankle. My right leg also has circulation problems, as well. I don't want to take any chance of making the situation worse. The tilt chair looks interesting and I have used an ergonomic chair in the past, but if you are experiencing any swelling in the legs, having your legs dangle or in one position too long could prove a problem. Hope this is not the case and that you are just causing a nerve to "fall asleep." That can be related to just the way your body is lined up, trying a higher or lower cushion or moving forward or back on the cushion could help with that, too.
Wishing: In gladness and in safety,
May all beings be at ease.
---from the Metta Sutta