to the tubing the shape of the curve of the applied force resembled the shape of the force curve of the tubing the size of the applied force was only slightly larger than the force exerted by the pressurized tubing so that the applied force caused the tubing to be compressed it was found that reducing the pressure in the tubing did not result in a failure of the magnet to collapse the tubing and thereby fail to u201c pump u201d the fluid out of the tubing however increasing the pressure in the tubing slightly did cause the magnet to fail to collapse the tubing and therefore the fluid failed to u201c pump u201d out of the tubing embodiments of the present invention such as those shown in fig7 b could detect this failure to collapse the tubing and generate a downstream occlusion alarm again referring to fig1 b because the applied magnet collapsing force is greater than the tubing force at maximum pressure no additional forces need be applied to collapse the tubing energy is transferred from the field of the magnet to elastic energy in the tubing walls as the tubing transitions from an open to collapsed state in summary it was found in this experiment that no force was required to open the tubing under 0 pressure when the magnet force was not present an applied force from about u2212 5 ounces to about u2212 4 ounces was required to open the tubing when the magnetic force was present it was also found that the force required to collapse the tubing under maximum pressure without the magnetic force present varied from about 18 5 ounces to about 8 1 ounces the addition of the magnetic force caused the tubing to collapse entirely.