Patent GB-788103-A (GB)
Title: Improvements in and relating to the apparatus for the administration of anaesthetics
Inventor: MARRETT HENRY REX
IPC: A61M16/10
Filed: 1954-07-16
Abstract: 788,103. Anaesthetic apparatus. AIRMED, Ltd. July 18, 1955 [July 16, 1954], No. 20860/54. Class 81 (2). Anaesthetic apparatus comprising a rebreathing bag and a carbon dioxide absorber is provided with valve-controlled passages interconnecting the bag, the absorber and the inspiratory and expiratory conduits so that a circuit can be established from the expiratory to the inspiratory conduit either through the absorber, the bag and the absorber for to and fro operation, or through the absorber and the bag for circle operation, the change of circuit being effected without interruption in the supply to the patient. A control unit 10 is divided into two compartments 42, 44 by a ported partition 40. The upper compartment 42 is connected to two vaporizers 12, 14 which are connected to one another and to a rebreathing bag 30. The lower compartment 42 is divided by radial walls into three chambers, one of which is connected to the expiratory conduit 38 having a one-way valve 34 and the other two of which are connected with a soda-lime absorber 26 in such a way that gas passes from one to the other only by way of the absorber 26. A valve 22 comprising a ported cylindrical wall 61, a ported base 71 and a dividing partition 77 is rotatable within the upper compartment 42 and is set so that the ports in the valve 22 and the partition 40 register with one another and conduits leading to the control unit 10 in such a way that a circuit is established between the expiratory conduit 38 and inspiratory conduit 36 either through the absorber 26 and the rebreathing bag 30 for " circle " operation or through the absorber 26, the bag 30 and the absorber 26 for " to and fro operation or through the bag 30 alone when trichlorethylene is provided by one vaporizer 14. The absorber 26 comprises an inner container 86 for soda-lime 27 and an outer container 88 spaced from the inner container 86. The supply of gas from the vaporizers 12, 14 is controlled by knobs 13, 15. When the valve 22 is set for " to and fro " operation, on exhalation gas passes through oneway valve 34 into one chamber of the lower compartment 44, through ports in the partition 40 and the valve 22 to a first side of the dividing partition 77, through ports in the valve 22 and partition 40 into a second chamber of the lower compartment 44, through the absorber 26 to the third chamber of the lower compartment 44 and thence to the second side of the dividing partition 77 and the breathing bag 30. On inhalation gas passes in the reverse direction from the breathing bag 30 and through the absorber 26 to the upper compartment 42 and thence through the vaporizers 14 and 12 to the patient by way of the inspiratory conduit 36 and its one-way valve 32. When the valve 22 is set for " circle " operation the ports of valve 22 are arranged so that on exhalation gas passes to the first side of the dividing partition 77 of the valve 22 and thence through the absorber 26 to the second side of the dividing partition 77 and the breathing bag 30. On inhalation gas passes from the bag 30 to the second side of the dividing partition 77 and via the vaporizers 14, 12 to the inspiratory conduit 36. In a third position of the valve 22, gas is cut off from the absorber 26 so that gas passes from the expiratory conduit to the bag 30 on exhalation and on inhalation, from the bag 30 via the vaporizers 14, 12 to the inspiratory conduit 36. A locking device is provided which prevents the supply of gas from one vaporizer 14, which may contain trichlorethylene, unless the rotary valve 22 is set in the third position and which also prevents the valve 22 being turned out of the third position if gas is being supplied by that vaporizer 14. Other gases can be supplied to the apparatus as desired through a pipe 100.