A variable occlusion device includes a device housing having an occlusion track adapted to receive one or more loops of flexible tubing and having an arcuate reactive surface. The device also includes a rotor member mounted for rotation within the housing about a device axis. The rotor includes a number of carriage passageways or tracks, each passageway or track with an occluding member carriage and occluding member assembly movably mounted therein. The carriage and occluding member assemblies are each adapted to move between an extended position in which the occluding member bears against and collapses the tubing received in the occlusion track, and a retracted position in which the occlusion member is drawn away from and out of contact with the tubing in the occlusion track. The peristaltic device also includes a fluid distribution system for providing an operating fluid from a remote fluid supply under a desired pressure to the carriage passageways of the rotor. The operating fluid is used to control both the occluding force exerted by the occluding members upon the tubing and the position of the occluding members. In the preferred form of the invention, operating fluid containment bags are positioned within each carriage passageway or track for containing the operating fluid, which may be suitable gas, so that it may apply the desired occluding force but does not directly contact either the fluid passage walls or the carriage member. Also, the desired fluid pressure is preferably communicated to the carriage passageways or tracks through a rotary union with no rotating seals apart from a sealing bearing structure.