A positive airway pressure system, comprising: a. a housing having an interior configured to receive one or more components of the positive airway pressure system; b. a pressure source component which has a controllable drive motor and which is configured to provide breathable gas to a patient's airway passage; c. a head position sensor which is configured to be mounted to a patient's head, which is configured to sense the position of the patient's head and which emits a head position signal representing the sensed position of the patient's head; and d. a controller component which is configured to receive the head position signal from the position sensor, which is configured to determine a suitable pressure source output pressure for a sensed position of the patient's head and which is configured to generate a control signal representing the suitable pressure source output pressure in response to the sensed head position signal and which is configured to send the generated control signal to the controllable motor drive of the pressure source to control the output pressure of the pressure source in response thereto to provide the suitable pressure output pressure for the sensed head position, characterized in that the controller component has an algorithm representing a relationship between suitable pressure source component output pressure and head position signal and the controller component is configured to determine from the algorithm a suitable pressure source component output pressure corresponding to the sensed head position signal, wherein the algorithm defines a curve in which the rate of change of pressure source component output pressure is greater for head positions between 30° and 60° from a supine position. a. a housing having an interior configured to receive one or more components of the positive airway pressure system; b. a pressure source component which has a controllable drive motor and which is configured to provide breathable gas to a patient's airway passage; c. a head position sensor which is configured to be mounted to a patient's head, which is configured to sense the position of the patient's head and which emits a head position signal representing the sensed position of the patient's head; and d. a controller component which is configured to receive the head position signal from the position sensor, which is configured to determine a suitable pressure source output pressure for a sensed position of the patient's head and which is configured to generate a control signal representing the suitable pressure source output pressure in response to the sensed head position signal and which is configured to send the generated control signal to the controllable motor drive of the pressure source to control the output pressure of the pressure source in response thereto to provide the suitable pressure output pressure for the sensed head position, characterized in that the controller component has an algorithm representing a relationship between suitable pressure source component output pressure and head position signal and the controller component is configured to determine from the algorithm a suitable pressure source component output pressure corresponding to the sensed head position signal, wherein the algorithm defines a curve in which the rate of change of pressure source component output pressure is greater for head positions between 30° and 60° from a supine position.