I have one mad idea I did not have time to properly test – to use normal breathing to suck the air out of a latex sleeping bag.
E.g.: a hood with nose holes and a gag with a breathing tube. The breathing tube goes inside the bag. You breath the air in with your mouth (from the bag) and breath it out with your nose. If the sealing is tight enough, it should work.
See also this post.
Works i think.
I made a big bag out of Trask bags and tape once.. sliped inside and closed the top from the inside with an rope i think. I had a short tube to the outside that i could breath throu when i put it in my mouth. I breathed in throu my nose and out throu the mouth.. so it got tighter.
By the way… you can use that big plastic bags where you put trash in too.. if you cut the floor away of two of them, put one into the other and tape/glue the bottom and top together, you have an ring that can inflate where you can be between. You can put that all together in an normal sleeping bag too maybe so it is limited how far it expand to the outside.
I hope its understandable what i mean 🙂
Excellent experimentation. Please read my comments regarding inflated plastic bag at the neck, and two pink fleece bags stretched over the inner inflated one. My sexual fantasy finally realized!!!!!