A valve assembly for a medical device including a container including a first region and a second region, a first fluid inlet fluidly coupled to the first region, a second fluid inlet fluidly coupled to the second region, and a piston assembly disposed within the container. The container is configured to house an agent within the second region, the first fluid inlet is configured to deliver a first portion of pressurized fluid to the first region at a first pressure level, and the second fluid inlet is configured to deliver a second portion of pressurized fluid to the second region at a second pressure level that is less than the first pressure level. The piston assembly includes a valve configured to move from a first position to a second position in response to the piston assembly moving relative to the container.