This invention relates generally to a method for performing an endoscopic procedure.According to some aspects of the invention, the method comprises placing an endoscope shaft within a body cavity at a desired examination point, the endoscope shaft having a proximal end, mid shaft and a distal end, the distal end terminating in an endoscope tip, wherein the endoscope tip is proximal to the desired examination point, positioning a segment of a longitudinally opened overtube over the endoscope mid shaft, wherein the overtube including a longitudinal reclosable seam along an entire length of the overtube, an inner surface, an outer surface, a proximal end and a distal end, a positioning ring adjacent the distal end on the outer surface, at least one sealing band on the inner surface, and an independently positionable occlusion catheter terminating in an asymmetrical occlusion balloon at least one handle at the proximal end and on the outer surface for grasping and manipulation of the overtube within the body cavity. The method further comprises closing the seam of the segment of the overtube positioned over the endoscope mid shaft to form a longitudinally closed overtube and move the closed overtube over the endoscope shaft as guide within the body cavity and repeat the closing and moving till the overtube reaches the desired examination point, inflating the positioning ring to create a seal between the outer surface of the overtube and a body cavity proximal to the endoscope tip, wherein when inflated the positioning ring expanded asymmetrically around the overtube, inflating the at least one sealing band to create a seal between the internal surface of the overtube and endoscope shaft, passing the independently positionable occlusion catheter terminating in the asymmetrical occlusion balloon through a passageway along the overtube to enter the body cavity at the end of the overtube, manipulating the independently positionable occlusion catheter to a selected point wi
