A device designed for partial insertion into a patient's mouth (in between the lips) to facilitate access to the respiratory system. It is typically a small rigid or semi-rigid plastic hollow device with a shape and structure that enables an appropriate gastight seal and prevents collapse. It is typically attached, either directly or through other tubes/adaptors, to diagnostic and/or therapeutic respiratory devices (e.g., ventilator, inhaler, incentive spirometer, aerosol equipment, breath analyser, breath collector); connectors and filters may be included with the device. This is a single-use device.