A herniated or slipped disc occurs when the soft material in the center of an intervertebral disc extends beyond the normal limits of the disc. Bulging discs swell when the soft material pushes to one side of the disc. Spinal decompression therapy creates negative pressure in the discs through gentle lengthening of the spine, which takes pressure off pinched nerves and can help reposition bulging discs or pull extruded disc material back into place.