Apparatus and method for providing gases to a user

A respiratory apparatus configured to deliver a flow of gases to a user, the apparatus comprising:

• a flow generator configured to generate the flow of gases;
• at least one sensor configured to measure properties of the gases;
• and
• a controller in communication with the flow generator and at least one the sensor, the controller configured to operate according to a pressure control mode and a flow control mode, wherein in the flow control mode a flow rate of the gases is substantially constant or within a limited range and is delivered at a sub-therapeutic pressure, and in the pressure control mode the gases are delivered at a substantially constant, therapeutic pressure, wherein the controller is configured to operate in the flow control mode when the user is determined to be awake and operate in the pressure control mode when the user is determined to be asleep,
• wherein, in the flow control mode, the controller is configured to control the flow rate of the gases to be above a minimum threshold, the minimum threshold being set to correspond to a particular type of a plurality of types of user interface used by the user, said plurality of types of user interface comprising:
• a full-face mask, and
• at least one of:
• a nasal mask, an oral mask, an oral interface, a nasal pillow, a nasal seal, or a nasal cannula;
• said minimum threshold configured to enable flushing of the particular type of user interface;
• and
• wherein, in the flow control mode, the controller is configured to determine an indication of carbon dioxide rebreathing or flow starvation by detecting an increase in a respiration rate or an increase in a breath volume of the user and adjust the flow rate in response to the determined indication by boosting a target flow rate or a target flow rate range during inhalation of the user.