A gas ratio control device for anesthesia apparatus, includes an anesthetic gas feed line, which has, in a series-connected arrangement, a control valve with an inlet chamber, an anesthetic gas-adjusting valve and a first measuring resistance, and an oxygen feed line, which has a second measuring resistance,...http://www.google.es/patents/US5537993?utm_source=gb-gplus-sharePatente US5537993 - Gas ratio control device for anestesia apparatus
