This tube is extensively used for controlling variceal bleeding as a temporary treatment or as definitive management prior to endoscopy management.
The tube is made of latex or India rubber and essentially has three channels. The main wide channel is used for gastric lavage. It has a closed tip with multiple openings on the side of the tip. The second channel runs through the main channel, hugging the wall and running parallel to the main channel. It opens distally into a rounded balloon that is placed just proximal to the tip. The proximal end of the second channel opens into a valve adjoining the main channel. Inflating through this valve, the balloon, which is also called a gastric balloon, inflates and, when hitched, compresses the varices against the cardia on its undersurface, temporarily arresting the variceal bleeding. The third channel also hugs the main channel on the opposite side and opens into an oesophageal balloon, which, when inflated, inflates the longitudinal balloon and is meant for tamponade on varices in the oesophagus. The valve to inflate the longitudinal balloon is at the same level as the gastric valve. The tube is calibrated, showing the gastric balloon level and the oesophageal balloon level. The main channel is long enough to reach the pylorus. This tube is only used to arrest bleeding varices in portal hypertension. The main channel is used for gastric washing and to clear blood, which if absorbed distally can lead to hepatic encephalopathy. One modification of an SB tube is known as a Linton’s modification. This modified tube has no oesophageal balloon and the gastric balloon has a capacity of 500 mL; it is used for gastric tamponade only. Another modification is Minnesota’s modification; this has four lumens, three of which are as in an SB tube and the fourth one opens proximal to the oesophageal balloon for aspiration of the oesophagus and so that the saliva is aspirated. Any of these modifications of the balloons are used in a collapsed state and are passed either through the nose or more commonly through the mouth after lubricating well. Traction is given on the tubing over a cricket helmet for pressure tamponade.
It is important to note that, because of recent developments in emergency medical management and endoscopic and radiological techniques in the management of emergency variceal bleeds, the use of these tubes has reduced significantly.