Left lateral position (Fig. 4.1a): left lateral position is the routine position for endoscopic examination. All physicians conducting endoscopic examinations should be well aware of the anatomic orientation of the esophageal wall under this position so as to choose the optimal esophageal wall for tunnel establishment in different operations [1–3].

Supine position (Fig. 4.1b): supine position is the routine position for the anesthetist to perform intubation, which is suitable for the operation of lesions located at certain parts of the esophageal wall. However, the head position of the patients make it slightly more difficult to push the endoscope forward [4, 5].

Supine position with right should lifted (Fig. 4.1c): this is a position between the left lateral position and the supine position, with less distorted neck and the mouth of the patient directed towards the operator.

The site where the submucosal tunnel is established should be in line with the site of the lesion to be resected. For a mucosal lesion, the upper entry incision site generally lies above the oral mark line, and the lower entry incision site lies below the anal mark line (Fig. 4.2a, b). For SMTs originating from muscularis propria, the entry incision should be done at the oral side of the tumor and about 2.5 cm above the tumor to establish a tunnel (Fig. 4.2c). For esophageal achalasia, although peroral endoscopic myotomy could be performed at any side wall of the lower esophagus and the cardia, it is best to choose a side wall farthest away from the descending aorta and the inferior vena cava to minimize the chance of hemorrhage, so the lesser curvature side wall of the cardia is recommended for tunnel establishment and myotomy because it has a smooth curvature during the establishment of the tunnel and will less possibly cause a tunnel perforation (Fig. 4.2d). For lesions outside of the muscular propria, the entry incision should be at the oral side of the lesion and about 3 cm above the lesion to establish a tunnel throughout the muscularis propria to the lesion outside the digestive lumen.

The entry incision should be located at the anal side of the lesion during peranal establishment of a submucosal tunnel, which is contrary to the choice of the oral side of the lesion for entry incision during peroral tunnel establishment, but the other procedures of tunnel establishment are the same between the two operation routes.

The types of entry incision during esophageal tunnel technique generally include the transverse incision and the longitudinal incision, while the arc incision is a third mutated type of incision from tunnel technique.