Abstract: A guide tube is used with a medical endoscope. The guide tube includes an elongated tubular member and a lubricating fluid. The elongated tubular member has an inner annular membrane, an outer annular membrane, a proximal end portion, and a distal end portion opposite the proximal end portion. The inner and outer annular membranes define a longitudinal axis extending between the proximal end portion and the distal end portion. The lubricating fluid is disposed between the inner annular membrane and the outer annular membrane. The lubricating fluid is disposed between the distal end portion and the proximal end portion. The inner annular membrane moves in a first axial direction along the medical endoscope as the medical endoscope is moved through a patient. The outer annular membrane correspondingly moving axially, but in a second, opposite axial direction, along the medical endoscope as the medical endoscope is moved through the patient.