Abstract: Objective To compare and observe the variation of pressure on two left-sided double-lumen endobronchial tubes caused by shift off from the ideal position.Methods A total of 41 cases of American Society of Anesthesiologists(ASA)Ⅰ - Ⅲ patients(gender not limited) aged between 29 and 81 years old who had been scheduled for elective thoracic surgery were randomly divided into two groups:Tuoren double-lumen endobronchial tube group(group T,n =21) and Smith double-lumen endobronchial tube group (group B,n = 20 ).After anesthesia induction,group T was inserted orally with the common type of left-sided double-lumen endobronchial tube made by Tuoren Medical Instrument Co.,Ltd.,whereas group B was inserted orally with the corresponding type of Portex? Blue Line? left-sided double-lumen endobronchial tube.Under the visual assistance of fiberoptic bronchoscope,the top edge of the bronchial cuff of double-lumen endobronchial tube was just located under the ridge of the carina,where was also the “0.0 cm position”designed in the present study.The indication cuff was connected with a disposable pressure sensor via three-way stopcock.The bronchial cuff was filled with air via a three-way stopcock in order to achieve a pressure up to 30 cmH 2 O.Then,the tube was retracted outward in 0.5 cm,until to the 2.0 cm position.Meanwhile,the pressure of bronchial cuff at each position was respectively recorded.Results The pressure on the 2.0 cm position was lower than that on the initial position(30 cmH2 O)in both groups(P <0.01).In both groups,when the tube was moved from 0.0 cm to 2.0 cm position,a decrease tendency of the pressure in bronchial cuff was exhibited (P < 0.01 ).Moreover,the amount and rate of decrease in overall pressure of bronchial cuff in group B were more than those in group T(P <0.01).Conclusion When the two kinds of double-lumen endobronchial tubes were shifted from the ideal position,the pressure of bronchial cuff was accordingly reduced.But,the amount and rate of reduction in the pressure of bronchial cuff of Smith double-lumen endobronchial tube were more than those of Tuoren double-lumen endobronchial tube.

Key words: bronchoscopy, air sacs, tonometry, catheterization