The Original TheraBubble is a bubble PEP, or positive expiratory pressure, device created by physiotherapists in Australia to help clear phlegm from the lungs and improve ventilation. The user breathes out through a long flexible tube into a water-filled bottle, and the resistance generated as the air bubbles through the water assists the movement of secretions. Fixed tubing and a series of water-level markings on the bottle allow the pressure to be set precisely and repeated from one session to the next for patients of any age. A one-way valve is fitted to reduce the risk of water being swallowed, inhaled or aspirated, and that valve also means the device delivers non-threshold PEP, with the instruction manual describing an alternative assembly for threshold PEP. It is made in Australia from medical-grade plastic for single-patient use.

Airway clearance usually has to be repeated through the day, so a device that is quick to assemble, easy to hold and simple to take apart for cleaning is more likely to be used as intended at home as well as in hospital. The marked water levels let a consistent resistance be set and reproduced without supervision, and the one-way valve addresses the main practical concern with bubble devices.