Patent GB-716803-A (GB)
Title: Apparatus for the administration of analgesics and anaesthetics
Inventor: BURNS THOMAS HENRY STEWART
IPC: A61M16/18
Filed: 1951-11-13
Abstract: 716,803. Respiratory appliances. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Nov. 3, 1952 [Nov. 13, 1951; April 4, 1952], Nos. 26571/51 and 8734/52. Class 81(2) An analgesic inhaler comprises a conduit having a first opening at one end to admit oxygen containing gas, a second opening at the other end through which the patient inhales, a constriction in the conduit, a reservoir for analgesic liquid, a duct of small cross-section for conveying analgesic from the reservoir to the conduit in the vicinity of the constriction, a third opening between the constriction and the second opening in communication with the source of oxygen containing gas a valve to regulate the size of the third opening under control of the pressure reduction on inhalation so that the analgesic oxygen-containing mixture is diluted in greater or less degree as the pressure reduction exceeds in greater or less degree a predetermined threshold value. The apparatus comprises a tube 6, Fig. 1, which passes through a container 1 for analgesic, e.g. that known under the Registered Trade Mark "Trilene." One end 8 of the tube 6 is connected with the patient so that air or a suitable gas mixture is drawn through the tube 6 as the patient inhales. The tube 6 contains a venturi tube 11 to the throat 10 of which analgesic is supplied by two hypodermic .needles 9. A length of triple-warp phosphor bronze wire gauze 19 is provided within the tube 11. The interior of the analgesic container 1 is connected with the atmosphere through an air leak 20. A valve 21 is provided near the end' 8 of the tube 6 to allow an additional intake -of air if the patient's depth of breathing causes an undesirable increase in the amount of "Trilene" admixed with the air. The air inlet end 7 of the tube 6 and the inlet to valve 21 may be protected by a wire gauze cage to prevent blockage. A filling aperture 2 having a horizontal part 4 is provided, filling being effected with part 4 vertical so that overflow indicates filling is completed. In another form of the invention. Fig. 4, a tube 15<SP>1</SP> having a venturi-shaped bore passes through an analgesic container 4<SP>1</SP> and projects into a container 1<SP>1</SP> secured below the analgesic container 4'. The container 1<SP>1</SP> is provided an outlet tube (not shown), having an adjustable air inlet, which is connected with the patient. When the patient inhales, air is drawn through an opening 42 in a shroud 38 and thence through the venturi-shaped bore of the tube 15<SP>1</SP> into the container 1', a wire gauze cylinder being fitted to the tube 15'. Analgesic reaches the throat 29 of the venturishaped bore by way.of apertures 21<SP>1</SP> in a baffle 20<SP>1</SP> surrounding the tube 15' and passages 26, 25 and an opening 28 in the tube 15<SP>1</SP>. A tube 37 having an air inlet within the shroud 38 allows extra air to pass to the container 1<SP>1</SP> through a lift valve 34 in the event of the depth of breathing of the patient causing the concentration of "Trilene" in the final mixture to become undesirably great, e.g. over 0.06 per cent. The analgesic container 4<SP>1</SP> is connected with the atmosphere through an air leak 23. A filling chamber 10<SP>1</SP> having a filling orifice 12<SP>1</SP> and overflow orifices 14<SP>1</SP> is provided. A rod 47 causes blockage of the passages through which analgesic reaches the interior of the tube 15<SP>1</SP> if the apparatus is not in a suitable position for operation, the rod 47 being moved into blocking position by the action of a weight 55. The tubes 6 -and 15<SP>1</SP> may be made of lead, brass or stainless steel and the containers of tin plate or aluminium. In another embodiment (not shown) the passages through which analgesic flows to the venturi tube are blocked when the device is not in an upright position by rods connected with a further rod slidably fitting in a bore in the tube 15<SP>1</SP> and projecting below the bottom of the apparatus.