A tissue modification apparatus includes a first and a second guide, a first and a second set of mounts, and a first and a second actuator. The valve member may include a valve stem, a valve head, a face formed on the valve head, a sealing surface disposed between the face and the perimeter of the valve head, a tapered socket, and a bevel. 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. An electronic controller has a processor that executes a stored algorithm. Benchmark cycles may be run using conventional benchmark software, or, alternatively, synthetic code.