Controlling a respiratory support system

A control system for controlling a respiratory support system for supplying therapy gas to a subject, the control system comprising:

• processing circuitry communicatively coupled to an interface for receiving an indication of a combination of the subject's head orientation and torso orientation,
• wherein the indication is based on orientation data provided by a sensing system configured to detect the subject's head orientation and torso orientation;
• wherein the interface is further configured to receive an arousal indication and
• a machine-readable medium storing instructions which, when executed by the processing circuitry, cause the processing circuitry to:
• identify, from parameter information associated with each of a set of different combinations of head orientation and torso orientation, a parameter value of the therapy gas for the respiratory support system to use in supplying the therapy gas to the subject for the indicated combination of the subject's head orientation and torso orientation;
• and cause the respiratory support system to supply the therapy gas with the identified parameter value;
• and
• in response to receiving the arousal indication, cause the respiratory support system to supply therapy gas with the parameter value at a default value, and vary the parameter value at a predefined rate until reaching the parameter value identified for the indicated combination of the subject's head orientation and torso orientation.