Pressure is measured on both sides of an occluding member for determining when pressure forces the occluding member may cause migration of the occluding member. An alarm indicates when the pressure force on the balloon exceed a predetermined threshold. In another aspect of the invention, a pressure monitor determines when a rate of pressure increase with respect to the fluid volume in the balloon reaches a predetermined threshold when inflating the occluding member. A predetermined amount of fluid is then added to the occluding member so that the balloon is not under inflated or over inflated.