Patent GB-1351326-A (GB)
Title: Automatic therapeutic ventilators
IPC: A61M16/18
Filed: 1971-12-09
Abstract: 1351326 Lung ventilators W J PHILIPS 9 Dec 1971 [11 Dec 1970] 57153/71 Heading A5T Lung ventilator comprises a bellows 64 for receiving oxygen from a cylinder 29 via a control valve assembly 50, and a bellows 78 for receiving oxygen from the bellows 64 via the valve assembly 50 and atmospheric air through a filter 34. Oxygen passes from the cylinder through a regulator 44, a solenoid valve 46 and a valve 48, via a flap valve 54, to expand the bellows 64 against the weight of a rod 60 and a metal disc 72. The solenoid valve 46 then closes and oxygen bleeds through orifice 74 so that a flexible portion 56 of diaphragm 52 is lifted from its seat and flap valve 54 is closed, thus allowing oxygen to be forced from bellows 64 by the weight of the rod and disc through the valve assembly 50 and flap valve 76 to the bellows 78, where it is mixed with the air entering through the filter 34. The filling of bellows 64 coincides with an inhalation period, and the transfer of oxygen to bellows 78 coincides with an exhalation period. Compressed air passes from a cylinder 35 via a regulator 138, a solenoid operated valve 140 and a valve 142, and through a flap valve 148 of valve assembly 144 (which is interchangeable with assembly 50) to compress the bellows 78 and expel the breathing mixture therein to a humidifier 86, containing an electric heating element 88. From the humidifier breathing mixture passes to the lungs via flap valve 102 of a breathing control valve assembly 98. The solenoid valve 140 is then closed and air bleeds from the system via orifice 156 of valve assembly 144, and through the variable orifice assembly 180 which may be adjusted to control the amount of time the breathing mixture remains in the lungs, since the rate at which air escapes therefrom controls the rate at which the diaphragm 100 lifts from the valve seat 106 to allow exhaled air to pass to a spirometer 116. At the same time the closing of valve 140 enables the bellows 78 to expand to receive oxygen from the bellows 64 and closes the poppet valve 132 to allow exhaled air to fill the spirometer bellows 118. On the next inhalation valve 140 is opened to allow air to compress bellows 78, and at the same time lifts poppet valve 132 to allow exhaled gas to escape to atmosphere. To provide a sigh the solenoid valve 162 is opened to allow more compressed air into the bellows casing 154 and thus collapse bellows 78 completely. Alternatively, Fig. 2 (not shown), a sigh may be provided by lengthening the period for which the compressed air and oxygen solenoid valves are open. An electric control circuit comprising a cycle timer, pressure control means, sigh control means, an alarm, and a power fail alarm, Fig. 3 (not shown), controls the opening and closing of the solenoid valves and operates alarms in case of power failure, loss of pressure, or high pressure. The ventilator may be operated in a fully automatic, a semi-automatic, or a "patient-triggered" mode, in which the patient's breathing is supplemented by the ventilator. In a structural form of the apparatus, Figs. 5 and 6 (not shown), the bellows for the oxygen, breathing mixture and spirometer, and the humidifier, are mounted on four trays each slidably mounted between two T-shaped support members, with the oxygen bellows above the breathing mixture bellows, and the spirometer above the humidifier, the controls being positioned in a base.