Abstract: A respiratory filter included in a respiratory system used in anaesthesia and/or patient ventilation, comprises a two-part housing 15 and 16 having coaxial ports 13 and 14 for connection to breathing tubes. Optionally a heat/moisture exchanger 25 spans the housing in addition to a planar filter member 24 which is held between parts 15 and 16 so as to be perpendicular to the direction of gas flow through the housing. According to the invention deflectors 30 and 19 are located relative to the ports 13 and 14 so as to spread incoming gases over the opposed surfaces of members 24 and 25 in order to utilize their total surface areas, thereby reducing the overall size of the filter and reducing "apparatus dead space". Each deflector has a through bore so as to utilize also the central area of the filter. Curved fins 26 and 27 radiate from each port 13 and 14.

Abstract: A water trap for a respiratory airline comprises a top and base the respective openings of which mate when they are releasably connected e.g. by a bayonet-joint. The opening of the top is partially spanned centrally by a disc, leaving an annular pathway for water around the periphery of the disc. A resilient annular sealing member connected at its outer periphery to the top makes sealing contact with the disc when the base is removed, but when the base is connected to the top the upper periphery of the base raises the sealing member to allow water to fall from the top and be collected in the base.

Abstract: Axial displacement between two components of a valve occurs as a result of relative rotation through the cooperation of helical ramps. Preferably another pair of helical ramps is provided concentric with the first but angularly offset 180.degree. with the result that when the components are at maxinum axial separation the residual contact between the ramps of each pair (shaded areas in FIG. 5e) will be on opposite sides of the axis x of rotation and prolongation, thus preventing tilting of the one component out of axial alignment with the other component. In other constructions more than two pairs of ramps are employed. The ramp means of the invention replaces a screw-thread to provide adjustment of the loading of a valve spring and permits the use of more economical manufacturing and assembly techniques.

Abstract: A valve is provided primarily for medical or surgical aspiration equipment. The valve is interposed in an air line between the low pressure side of a pump and a collecting bottle for body fluid. The valve chamber has a sump-like bottom in which any liquid or froth entrained in air drawn in at a higher position will collect, and the valve member defines with said bottom narrow air admission apertures which are readily occluded by such liquid or froth, thereby producing a pressure difference across the valve member which displaces it to the valve-closed position.