A system (10) for delivering respiratory therapy to a patient comprises a patient interface device (20) for delivering pressurised gas to a patient, a connector system (60) for connection to a source of pressurised gas and a conduit system (40) fluidly connecting the connector system (60) to the patient interface device (20). The connector system (60) includes a plurality of closable ports (68, 32) that allow a plurality of different modes of respiratory therapy to be provided. The conduit system (40) may include a first gas line (42), a second gas line (46) and a third gas line (46). The second gas line (46) and third gas line (44) may be contained within the first gas line (42) along at least part of their length.
