Abstract: A tracheal tube assembly includes a dual balloon system upstream from the tracheal cuff and located externally to the patient. A pre-determined amount of air may be injected through a one-way valve into the innermost balloon which is of relatively low compliance. Expansion of the inner balloon passively expands the high compliance outer balloon. When the inner balloon is preloaded the system is ready for use. Opening of a control valve selectively interconnects the inner balloon with the surrounding relatively high compliance outer balloon via a high resistance inlet and with the tracheal cuff via a low resistance inlet so that the tracheal cuff is preferentially inflated. Equalization of pressure in the system rapidly occurs and this pressure is determined and maintained at a constant level by the characteristics of the high compliance outer balloon. The control switch can be positioned to allow the tube to function in a non-pressure regulated mode as in the conventional tube.