Abstract: A gas switching device for use with a gas supply system in which two gases, for example, oxygen and air are supplied to a medical unit comprises a manifold 106 to which are attached two identical valve assemblies 108, 110. The manifold has a first inlet 1 and outlet 5 for the passage therethrough of the oxygen and a second inlet 2 and outlet 6 for the air. Each valve assembly 108, 110 includes a spool valve 122 movable from a first to a second position under the influence of the pressure of its associated gas. At least one valve assembly 110 has an inlet 18' communicating with a passageway 15 in the manifold which, in turn, communicates with the inlet 1 for the oxygen and an outlet 22 communicating with a further passageway 16 in the manifold which in turn communicates with the outlet 6 in the manifold for the air.

Abstract: An anaesthetic vaporizer of the by-pass type has a sump 7 with an outlet flow path comprising a first run 27 leading upwardly, a second run 30 leading downwardly and a third run 32 leading upwardly again. A duct 23 connects the lower end of the run 30 with the lower part of the sump and in normal operation is sealed by the sump liquid. However, if the vaporizer is displaced such that the liquid flows from the sump into runs 27 or 30 of the outlet flow path the liquid inevitably drains from the duct 23. A flow path for inflowing gas is thereby opened directly to the downstream end of the run 30, preventing the over-administration of vapor from the device and removing any danger of liquid anaesthetic being blown through the device from the runs 27 and 30.

Abstract: A gas flow unit such as a vaporizer mountable on a gas administration apparatus such as an anaesthesia machine in plug-in fashion includes an interlock system which prevents a valve for controlling the admission to the unit of gas from a supply provided by the apparatus from being operated before a locking mechanism has locked the unit to the anaesthesia machine.The interlock system also includes actuating means which when the unit is mounted on the anaesthesia machine, opens respective valve members in ports located on the anaestheia machine only when the control valve is moved to its operating position.In the case when two similar units are mounted side-by-side on the anaesthesia machine and intended for use as alternatives, the interlock system includes pins which when the control valve on one unit is moved to its operating position, extend outwardly from the unit to prevent the control valve on the other unit from being operated.

Abstract: A device in the form of a flexible intravascular probe for use in analyzing absorbed blood gases includes a gas-permeable membrane 10 comprising two layers in intimate contact and supporting each other. The permeability of the second layer 6 is significantly less than that of the first 5, and provides the desired permeability of the membrane 10 as a whole. The first layer 5 provides the desired mechanical compatibility and other properties of the membrane 10.

Abstract: A gas permeable probe for use in the analysis of absorbed gases in liquids, notably in the blood, by mass spectroscopy, comprises a flexible plastics capillary tube fitted at one end with a plug of porous material and covered with a protective layer of polymeric material. The gas permeability of the porous plug is substantially less than that of the polymeric layer so that it is the plug which defines the gas flow from the liquid under test into the tube when the tube is evacuated.

Abstract: A device for mounting an accessory on a generally vertical column. The column preferably forms part of a support for an anaesthetic or like machine. The mounting device comprises a ring clamp adapted to engage the column at a chosen location (which may be adjustable), a split bearing adapted to embrace the clamp so as to be capable of only pivotal movement about the clamp and column, and means for securing an accessory onto one element of the bearing.

Abstract: A transcutaneous probe for causing oxygen and other gases or vapors carried in the bloodstream of a mammal to be extracted from the blood through the skin and passed to a device, such as a mass spectrometer, for analyzing the extracted gas. The probe has a boundary wall intended to be placed in contact with the skin comprising a first layer of gas permeable material and a second layer of perforate or porous gas-impermeable material in intimate contact with the first, the size and distribution of the perforations or pores in the second layer being such that the wall has a substantially uniform extrinsic macropermeability which is significantly lower than the inherent permeability of the first layer alone and such that in use, gas passes into the perforations or pores of the second layer from respective volumes of tissue which do not substantially overlap.

Abstract: A lung ventilator which transmits from a bellows respirable gas and/or anaesthetic gas directly to a patient during the inspiratory phase of the patient's breathing cycle and in which, during the expiratory phase of said cycle, the patient exhales directly into a rebreathing bag and at some time during this latter phase, the bellows is caused to inflate to thereby draw in exhaled gas both directly from the patient and from the interior of the rebreathing bag. The bellows and rebreathing bag are isolated one from the other by a biassed flow control valve situated in a conduit linking them together, which valve will allow the contents of the rebreathing bag to be emptied into the patient by squeezing the bag at any time during operation of the ventilator.

Abstract: A device including a chamber having two inlets and an outlet. One inlet is connected to an expiratory valve in a lung ventilator or like machine, the other inlet is in communication with a whistle and the outlet is connected to an aspirator. The device gives an intermittent audible signal when the ventilator is operating and saves the operator of the ventilator from having to look at the expiratory valve thereof to verify its correct operation.