Patent ID: 8205610

Claim:
A delivery apparatus for pressurized medical liquids, comprising: a reservoir containing a medical liquid within an inner wall of said reservoir, said medical liquid having a continuous liquid surface in said reservoir, and a pressurizer that pressurizes a gas above said liquid surface in said reservoir the medical liquid, said reservoir having an upper portion above said continuous liquid surface and a refill inlet disposed in said upper portion allowing refilling of said reservoir with medical liquid, and said reservoir having an outlet located below said liquid surface and a controllable valve in fluid communication with said outlet that controls discharge of said medical liquid, forced by said pressurizer, via said outlet; and a diffusion barrier that floats unrestrained on the liquid surface on the medical liquid in the reservoir, said diffusion barrier having size that covers said liquid surface of said medical liquid in said reservoir except for a peripheral gap between said inner wall and said diffusion barrier in a range between 0.1 mm and 1 mm, and said diffusion barrier being comprised of a material that, in combination with said size of the diffusion barrier, prevents diffusion of gas in the reservoir into the medical liquid.