Measurement of the flow-resistive properties of double-lumen bronchial tubes in vitro.

This study measures the resistance to gas flow of different double-lumen bronchial tubes used for separate ventilation of each lung in critically ill patients. Different-sized Robertshaw and Carlens' tubes were studied, as well as a new device that consisted of a cuffed bronchial catheter introduced through a standard tracheal tube. The pressure-flow relationship was curvilinear in all cases. Robertshaw and Carlens' tubes were generally found to have bronchial and tracheal channels with almost similar resistance and offered total resistances similar to those of 7.0-8.0 mm internal diameter tracheal tubes. The new device had a higher resistance than others of equal external diameter. This must be taken into account when its use is recommended for prolonged respiratory support.