The univent tube is an endotracheal tube with a movable bronchial blocker for one lung ventilation. The purpose of this study was to measure the appropriate cuff volume sealing the mainstem bronchus by three different techniques.

This study was performed in 60 adult patients undergoing thoracotomy. 1) The negative pressure was applied to the end of blocker causing loss of volume in the breathing system. The blocker cuff volume was measured at the point of the bag ceased to deflate. 2) The blocker cuff volume was measured when breathing sound is not heard on blocked lung. 3) Then the capnometer was applied to the blocker and the cuff volume was measured at the point of the CO2 wave ceased abruptly. The bronchial blocker volumes from these three methods were compared with the volume which was measured when the lung was completely collapsed in operation field.

Left bronchial sealing volume was 2.7±?0.8 ml with negative pressure technique, 3.5±0.8 ml with auscultation, 3.2?1.2 ml with CO2 technique and 3.0±0.7 ml with complete lung collapse at operation field. Right bronchial sealing volume ranged 3.5±0.9 ml with negative pressure technique, 4.6±1.0 ml with auscultation, 3.9±0.6 ml with CO2 technique and 4.2±0.9 ml with complete lung collapse at operation field.

We concluded that right bronchial blocker volume was 4.2±0.9 ml and left bronchial blocker volume was 3.0±0.7 ml. The right bronchial blocker volume was larger than the left.