Patent GB-929434-A (GB)
Title: Apparatus for pulmonary ventilation
IPC: G04B47/06
Filed: 1959-07-09
Abstract: 929,434. Artificial respiration apparatus. F. FRANZ. July 9, 1959 [July 16, 1958; May 15, 1959], No. 23601/59. Class 81 (2). Artificial respiration apparatus comprises a pump 23, 24 for delivering gas to and withdrawing it from a mask 10, the pump being in pressure communication with the mask, the rate of flow of gas to the mask being controlled by a movable valve 86 which is adjustable in response to pressure in the mask to any one of an infinite number of positions between its extreme positions. A face mask 10 is connected through a carbon dioxide absorber 16 and anµsthetic bottles 17 with a breathing bag 315 which is located in a chamber 316, one-way valves 18, 19 ensuring that only inspiration air receives anaesthetic gas and only expired air passes through the absorber. Alternating positive and negative pressures are produced in the chamber 316 by the pump which comprises a piston 24 which reciprocates in a cylinder 23 so that the bag is alternately collapsed and expanded to induce respiration in the patient. The pressure in the mask is transmitted by a pipe 30 to a tambour 32 which includes pressure-responsive diaphragms 33, 34. At the end of an inspiration, one diaphragm 33 is displaced sufficiently for an armature 42 connected to it through a valve 36, to come within the influence of a first magnet 44 which switches the valve 36 so that oxygen from a container 41 is supplied to one side of a main valve 54. The main valve is then changed over to permit oxygen to flow to one side of a piston 62 which is operatively coupled to the pump piston 24 by a rod 63. The piston 24 is thus caused to withdraw gas from the chamber 316 and bring about expiration. At the end of each expiration the mask pressure is sufficiently low for the tambour diaphragm 33 to move the armature 42 away from the first magnet 44 and towards a second magnet 43 so that the valve member 36 reverses. Gas is then supplied to the other side of the main valve and the other side of the piston 62 so that the pump piston 24 compresses gas in the chamber to induce an inspiration. The spacing of the magnets 43, 44 is adjustable so that the maximum and minimum pressures attained in the mask may be varied. A butterfly valve 86 in a casing 21 between the pump and the chamber is connected to the second diaphragm 34 so that the flow resistance between the pump and the chamber is varied during inspiration and expiration. Pivotal stops 107, 111 are arranged to engage the pivot 110 of the butterfly valve so that flow resistance is a maximum as the device changes from inspiratory to expiratory action and vice versa. In the event that the demand for oxygen increases beyond that supplied, the piston pump operates too near the bottom of its cylinder and additional oxygen from the container 41 enters the mask by way of the pipe 30 and a needle valve 100 which is opened by engagement of a lever 103 with a stop on the rod 63. The stroke of the piston 24 is indicated on a scale 27 which gives a measure of the patient's tidal volume. Apparatus (not shown) may be provided to give an indication of the tidal volume compensated for changes in pressure in the pump. A stop-watch 84 which is stopped and started in response to expiratory or inspiratory action of the device by a lever 81 associated with the oxygen supply to the piston 62, indicates the time of the respiratory cycles. A valve 13 disconnects the pump and connects a manually operable bag 11 to the chamber 316 if desired. The pump 23, 24 may be connected to the mask without the intermediary of the bag 315 and the chamber 316 (Fig. 4, not shown). Apparatus (Fig. 3, not shown) may be provided to vent the breathing bag if it becomes too full or supply it with additional gas, or to supply the pump with additional oxygen to compensate for leakage.