Cutting off circulation or asleep?

Basically I got a boot cast thing, which is air pressured. I can make it tighter or looser by adding or subtracting air. Now since its a cast, and I have to keep my heel still inside it (i have a hairline fracture and Achilles Tendant issues) it falls asleep. Now, I keep it pritty tight in the boot and my foot falls asleep every now and then. How do I know I don't have it too tight? How can I tell my foot is asleep or if it has no circulation? I know I can check but seeing how I'll have this in school after the break it will get very tedious to check every time. So how can I tell without having to open it every time? It really worries me lol.