The present invention is a dual lumen endobronchial tube provided with a flexible wall dividing a cylindrical main tube into two lumens, where the outside wall of the main tube is reinforced, preferably by metal wire but alternately by a sufficiently rigid polymer ribbing which will achieve a desired reduction necessary outside wall thickness. The achievement of a reduction in necessary wall thickness enables sufficient hydraulic cross sectional area so that each lumen is capable independently of providing adequate ventilation to a patient even while a ventilation lumen is partly occluded when the insertion end of a bronchoscope or tube is inserted into the adjacent lumen to examine or treat the other lung.
