A pressure adjustment apparatus, comprising: a pump including a pump body that defines a variable volume therein, the pump body further defining a first aperture and a second aperture therethrough, such that the first aperture and the second aperture of the pump body are in fluid communication with the variable volume; a selector valve coupled to the pump, the selector valve defining a plurality of fluid channels (32,34,36,38,40,42) therethrough, the selector valve including a first check valve disposed in a first fluid channel of the plurality of fluid channels (32,34,36,38,40,42), 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 third check valve disposed in a third fluid channel of the plurality of fluid channels (32,34,36,38,40,42), the third check valve being oriented to permit flow through the third fluid channel only in a second flow direction, the second flow direction being a flow direction into the variable volume; and a chamber in selective fluid communication with the pump through the selector valve, wherein when the selector valve is oriented in a first position relative to the pump, the first aperture of the pump body is in fluid communication with the first fluid channel of the selector valve, thereby permitting a flow from the variable volume of the pump into the chamber through the first fluid channel, and the third fluid channel is not in fluid communication with the pump, and wherein, when the selector valve is oriented in a second position relative to the pump, the first aperture of the pump body is in fluid communication with the third fluid channel of the selector valve, thereby permitting a flow from the chamber into the variable volume of the pump through the third fluid channel, and the first fluid channel is not in fluid communication with the pump. a pump including a pump body that defines a variable volume therein, the pump body further defining a first aperture and a second aperture therethrough, such that the first aperture and the second aperture of the pump body are in fluid communication with the variable volume; a selector valve coupled to the pump, the selector valve defining a plurality of fluid channels (32,34,36,38,40,42) therethrough, the selector valve including a first check valve disposed in a first fluid channel of the plurality of fluid channels (32,34,36,38,40,42), 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 third check valve disposed in a third fluid channel of the plurality of fluid channels (32,34,36,38,40,42), the third check valve being oriented to permit flow through the third fluid channel only in a second flow direction, the second flow direction being a flow direction into the variable volume; and a chamber in selective fluid communication with the pump through the selector valve, wherein when the selector valve is oriented in a first position relative to the pump, the first aperture of the pump body is in fluid communication with the first fluid channel of the selector valve, thereby permitting a flow from the variable volume of the pump into the chamber through the first fluid channel, and the third fluid channel is not in fluid communication with the pump, and wherein, when the selector valve is oriented in a second position relative to the pump, the first aperture of the pump body is in fluid communication with the third fluid channel of the selector valve, thereby permitting a flow from the chamber into the variable volume of the pump through the third fluid channel, and the first fluid channel is not in fluid communication with the pump.