A pressure adjustment apparatus including a pump, a selector valve coupled to the pump, and a chamber in selective fluid communication with the pump through the selector valve is disclosed. The pump includes a pump body that defines a variable volume therein, the pump body further defining a first aperture and a second aperture therethrough. The selector valve includes a first check valve disposed in a first fluid channel of a plurality of fluid channels, the first check valve being oriented to permit flow through the first fluid channel only in a first flow direction, the first flow direction being a flow direction out of the variable volume, and a second check valve disposed in a second fluid channel of the plurality of fluid channels, the second check valve being oriented to permit flow through the second fluid channel only in a second flow direction.