An adapter for connection between an oxygen flowmeter and a water bottle whose contents humidify oxygen fed to a patient. An audible duckbill valve is mounted on a valve seat transverse to the longitudinal axis of the connector. When oxygen pressure through the connector becomes excessive, the valve...http://www.google.es/patents/US4350647?utm_source=gb-gplus-sharePatente US4350647 - Permanent adapter for a medical humidifier
