An assembly of devices designed to conduct air or oxygen (O2) enriched gases and additional gases [e.g., nitrous oxide (N2O), halogenated gases] from a ventilator, or other air-delivery therapeutic device such as a mechanical insufflator/exsufflator, to a patient. It includes breathing tubes, a Y-piece connector, and provides connections for devices that humidify, deliver medication, and monitor gas concentration or pressure within the breathing circuit. This is a reusable device.