Use of tracheal ultrasound combined with clinical parameters to select left double-lumen tube size: A prospective observational study

BACKGROUND Left double-lumen tubes (LDLTs) are used in thoracic surgery to allow one-lung ventilation. Their size is usually chosen on the basis of clinical parameters (height, sex). Double-lumen endobronchial tubes are frequently undersized/oversized, risking tube displacement or tracheal trauma. A correlation between ultrasound tracheal diameter and left main bronchus dimension has been demonstrated. OBJECTIVES We hypothesised that the insertion of undersized/oversized double-lumen tubes is frequent when the size is selected using standard criteria, and that the use of ultrasound to estimate tracheal diameter may help to reduce the frequency of insertion of oversized tubes. DESIGN Two-step prospective observational study. SETTING The operating room of a French University hospital from January 2016 to February 2017. PATIENTS We enrolled 102 and 50 consecutive patients undergoing elective thoracic surgery in Steps 1 and 2 (males 63.7 and 60.0%, age 63 (13) and 63 (11) years, height 170 (13) and 169 (9) cm, respectively). INTERVENTION In Step 1, the size of the LDLT inserted was selected on the basis of clinical parameters. Ultrasound data about tracheal diameter were collected to determine cut-off points associating height and tracheal diameter. Cut-off values for ultrasound tracheal diameter were applied retrospectively to test their capability to reduce the insertion rate of oversized tube. In Step 2, the LDLT size was chosen according to the determined combined cut-off values. MAIN OUTCOME MEASURE LDLT size was considered adequate if the bronchial cuff volume required for isolation of the lung (i.e. no difference between inspiratory and expiratory lung volumes) was 0.5 to 2.5 ml of air; undersized and oversized tubes required more than 2.5 ml and less than 0.5 ml, respectively. RESULTS In Step 1, LDLT size was appropriate/undersized/oversized in 40 (39.2%)/23 (22.6%)/39 (38.6%) of patients. Cut-off values derived from ultrasound measurements would have reduced the use of oversized tubes by 20.6% (P 

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