An inflatable balloon is provided. The balloon includes a central lumen open at both ends of the balloon and connected to a gap formed in one sidewall of the balloon. This arrangement may provide the balloon with a generally C-shaped profile with the open central lumen within the balloon along a center axis thereof, such as to allow for perfusion. The balloon may also include an inflation port offset from a central axis and a shaft including an inflation lumen connected to the inflation port. A sheath may also be provided with a window through which the balloon may project in use.