Trachea, with tracheotomy tube (1 of 2)
Upper trachea, with tracheotomy tube in view.

Trachea, with tracheotomy tube (2 of 2)
When the patient exhales fully, the posterior (back-side) tracheoesophageal party wall flexes anteriorly (frontward) to obstruct the trachea just above tracheotomy tube entry.