An inflation device includes a syringe body containing a bore. The bore holds a fluid that is used to inflate a separate device such as a dilation balloon. A plunger assembly slides within the syringe bore and contains a sealing member that forms a fluid tight seal with the syringe body. A shut-off valve is disposed within the distal end of the syringe body. The distal end of the syringe body has a fluid bypass channel fluidically coupled to the aperture of a connector. The shut-off valve has a spring-biased moveable piston with a bypass lumen contained therein, wherein the bypass lumen forms a fluid path between the bore and the fluid bypass channel when the pressure of the fluid is below a threshold value. The fluid path between the bore and the fluid bypass channel is interrupted when the pressure of the fluid is above the threshold value.