Abstract: An apparatus for controlling the flow of gas to and from a patient in an anaesthesia system has first and second flow passages arranged in parallel between the patient and a reservoir bag. Selector valves allow multiple anaesthesia configurations involving no rebreathing or considerable rebreathing. A selector valve can be operated to connect the reservoir bag to either or both flow passages. A one way valve in the first passage, which communicates with a gas supply inlet, can be operated to prevent the back flow of gas from the patient into the passage. A one way valve in the second passage can selectively prevent the flow of gas in the second passage to the patient. The second passage has a selectively bypassable carbon dioxide absorbing fitter and a spill valve. The apparatus allows reconfiguration without disconnecting and reconnecting hoses.

Abstract: Gas mixing and flow smoothing apparatus for use in for example an anaesthesia system comprises a mixing chamber (8) which receives the flow of two or more gases via control valves (6,7). The mixing chamber (8) is adapted to absorb fluctuations in the pressure of the gases therein through the provision of for example a spring-loaded piston (not shown) which forms one wall of the chamber, and the pressure at the outlet (30) from the chamber (8) is maintained at a substantially constant pressure by means of a valve (9). If desired, further attenuation of the gas flow may be achieved through the provision of a second series arrangement of surge damper (11) and back pressure valve (10) located downstream from the valve (9).