For the test you will lie on your left side and local anaesthetic is sprayed into the mouth before a tube is inserted through the mouth.  You will be asked to swallow to help the tube into the gullet (oesophagus). Intravenous sedation is usually offered to patients. The tube, or scope, is similar to those used for detecting stomach ulcers, except that this one is fitted with a small ultrasound probe at its tip. 

The test itself usually takes about 20 minutes and you will need to rest afterwards in a recovery area until you are awake enough to go home.