Abstract: A respiratory breathing circuit prevents heat loss and condensation in a flow of humidified air through a conduit from a humidification system to a patient interface, such as a nasal cannula. The circuit directly impedes heat loss or insulates the flow of a humidified gas therein, and provides a heating source inside the circuit along the length of the circuit to prevent net heat loss from the circuit tubing by providing thermal energy and/or insulation to impede convective, conductive, or radiative heat loss by the gas as it flows through the system. A temperature, humidity, or other flow quality measuring probe is disposed at the distal end of the circuit near the patient interface to actively measure a corresponding quality of the humidified gas flow to provide feedback to the system. A pressure relief valve is provided on the circuit to prevent a pressure build-up and/or structural failure.

Abstract: A patient adapter for being connected to gas tubing in a ventilator circuit comprises of an inspiratory and an expiratory pipe, the latter having an internal diameter at least about 20% greater than the diameter of the inspiratory pipe. The invention also includes a respirator circuit in which an expiratory limb has an internal diameter at least about 20% greater than the diameter than the inspiratory tubing limb.

Abstract: A humidifier assembly includes a cartridge secured in the humidification chamber cavity for displacing between about 20% and about 80% of the volume of the cavity.