Ventilator

Abstract: A ventilator for supplying and emitting respiratory gas to and from the airways of a human being or an animal, respectively, is provided. The ventilator comprises a multiple-function safety valve (6) located between a control valve and the airways. The safety valve (6) is affected in its closing direction by two springs (13), which apply force that corresponds to a predetermined overpressure and in its opening direction by a spring loaded piston (22), which applies force that exceeds the force of the springs (13). By starting the ventilator, an electromagnet (20) is connected. The electromagnet (20) pulls the piston (22) against the force from the spring load (21), and the safety valve (6) closes. By means of a control device, the pressure in the inspiration section (3) can be supervised and the electromagnet (20) disconnected at a programmed overpressure. At power failures, the safety valve (6) will open and air can pass through the open safety valve (6) to the airways.

Description: The invention relates to a ventilator to be connected to the airways of a human being or an animal for supplying and emitting respiratory gas to and from the airways, respectively, which ventilator comprises an inspiration section through which the respiratory gas is lead to the airways, which inspiration section comprises at least one control valve for the gas flow and a safety valve, which is affected by a force load in the closing direction and a spring device in the opening direction, which safety valve is located between the control valve and the airways. An already known ventilator (7200 Microprocessor Ventilator, Puritan Bennett Corp., USA) is provided with an inspiration section, which is supplied with air and any additional gas from a compressed-air system. The respiratory gas hereby passes a system of control valves in order to obtain a desired pressure. To prevent a too high pressure in the lungs of a patient, the inspiration section is provided with a safety valve between the control valves and the patient. The safety valve is described in the ventilator service manual, pages 80 - 82 and accompanying drawing and comprises a valve that is affected in the opening direction by a spring and in the closing direction by an overpressure caused by air from the compressed-air system adjusted to a pressure corresponding to the pressure of the spring plus the maximum allowed pressure for the patient. The amount of closing pressure is dependent on the pressure of the compressed-air system as the valve that lets the pressure through to the safety valve only has two fixed positions; open and closed. The safety valve thus opens at an overpressure that exceeds the maximum allowed pressure for the patient. Furthermore, the safety valve automatically opens at power failures and at shortages of pressure from the compressed-air system, which makes it possible for the patient to get air through the open safety valve. As the closing force of the safety valve is dependent on a valve, there are risks for operational disturbances, should this valve become inoperative. The closing pressure could for example disappear if the valve ceases to function, and the safety valve would then open completely in spite of a correct respiratory gas pressure visavi the patient. An object of the present invention is to construct a ventilator such that previously known safety functions are retained but improved upon and such that the weaknesses are overcome and the construction is simplified and made safer. This object is achieved in accordance with the invention, cf. claim 1, in that; the safety valve comprises a plate, arranged to be pivotable between an open position, in which the safety valve is open, and a closed position, in which the safety valve is closed; the spring device is arranged to affect the plate in its opening direction; the force load is produced by at least one spring connected to the plate to affect the plate in its closing direction; the force from the spring device exceeds the force from the spring; the spring constant is selected so that the force load corresponds to a predetermined overpressure in the inspiration section; and an electromagnet is arranged to disconnect the effect of the spring device on the plate when supplied with current, whereby the safety valve is closed when the electromagnet is connected and open when the electromagnet is disconnected. Hereby the safety valve will be in an open position until the electromagnet is switched on, whereupon the safety valve takes its position as an overpressure protection. At, for example, power failures, the safety valve immediately opens as the electromagnet then is disconnected and the patient will get air via the open safety valve. As this system is completely independent of the compressed air supplied, the maximum overpressure allowed is well defined and the safety valve stays closed as long as the pressure of the respiratory gas falls below the maximum pressure. By providing the safety valve with an adjustment device for the spring, for example a tightening screw, a fine adjustment of the maximum allowed overpressure can be achieved, alternatively a variation within certain limits. A second solution is obtained in accordance with the invention, cf. claim 7, in that the safety valve comprises a plate, arranged to be pivotable between an open position, in which the safety valve is open, and a closed position, in which the safety valve is closed; the spring device is arranged to affect the plate in its opening direction; the electromagnet is attached to the plate and the force load is produced by the pulling force of the electromagnet when it is connected, whereby the force may be controlled by the current supply to the electromagnet so that it corresponds to the force from the spring device plus a force corresponding to a predetermined overpressure in the inspiration section. Hereby, all the functions and advantages of the first solution are obtained, but with fewer construction parts. With this solution, it is possible to adjust, even more accurately and within wider limits, the defined overpressure at which the safety valve shall open by varying the current to the electromagnet. It is advantagesous to have the ventilator of both solutions comprise a device for sensing the pressure in the inspiration section and to have the electromagnet disconnected at an adjustable overpressure, which is lower than the predetermined overpressure. The disconnection of the electromagnet may be achieved by a programmable control device, which disconnects the electromagnet at a programmed overpressure. In order to prevent occasional transitory peaks in the variation of the pressure from unnessecarily opening the safety valve, it is appropriate if the electromagnet is not disconnected until the pressure exceeds the adjustable/programmable overpressure plus a predetermined safety interval. It is an extra advantage of the ventilator that it can be adapted to each individual patient so that a programmed overpressure replaces the predetermined overpressure. The electromagnet will then be disconnected and the safety valve open at the programmed overpressure. In connection with four figures, a ventilator is described as an embodiment of the invention, whereby fig 1 shows a pneumatic unit of the ventilator, fig 2 shows a safety valve of the pneumatic unit in its open position, fig 3 shows the safety valve in its closed position and fig 4 shows an alternative embodiment of the safety valve. A pneumatic unit 1 of a ventilator, fig 1, comprises several inlets 2 for air and any additional gases, which are lead under pressure into an inspiration section 3 of the pneumatic unit 1. In the inspiration section 3, the additional gases are mixed with air and lead to a patient under a controlled pressure and in a measured amount. On its way out of the pneumatic unit 1, the gas mixture passes a bacteria filter 4, a pressure transducer 5 and a safety valve 6, which is marked by a broken line and located on the underside of the inspiration section 3. From the patient, the gas mixture and the expiration gas of the patient are lead to an expiration section 7 of the pneumatic unit 1. Also in the expiration section 7, the pressure is measured, and an expiration valve 8 regulates the pressure in the expiration section 7 to a desired level. The ventilator also comprises a not shown control unit, by means of which desired variables and parameters can be set and/or programmed. The safety valve 6 of the inspiration section 3 has several functions in this construction. It acts as a mechanical overpressure valve, which opens if a too high pressure is accumulated in the inspiration section 3 and thereby prevents the patient from being exposed to gas under pressure which could be damaging; it also acts as a supervising valve, which opens at a certain programmed overpressure, which is set by a physician, and as an emergency valve, which immediately opens at power failures, for example, and thereby provides the patient with air via the open valve. In order to further increase the safety of the patient, the ventilator is constructed such that when the safety valve 6 opens, for any of the mentioned reasons, the expiration valve 8 opens completely and the inspiration section 3 closes. In order to obtain these functions, the safety valve 6 is of a special construction, which is shown in figures 2 and 3. A plate 9 is in one end provided with an adjustment plate 10 on which a sealing disk 11 is fastened. The sealing disk 11 fits over the valve opening 12 and is pressed against it by means of two springs 13 (one is concealed by the valve), which are fastened to the plate and to two pins 14 (one is concealed by the valve) located above the valve opening 12. On the underside of the plate 9, a tightening screw 15 is located, through which the adjustment plate 10 can be moved vertically relative to the plate 9 and thereby enabling the springs 13 to be tightened, by moving of the adjustment plate 10 upwards, or unloaded, by moving the adjustment plate 10 downwards. The overpressure at which the safety valve 6 is to open can hereby be varied by varying the tightness of the springs 13. In order to keep the plate 9 in its correct position, two indentations 16 (only one visible) are cut out in the middle of the longitudinal sides of the plate 9, which indentations 16 fit around two legs 17 (of which one is sectioned off to show the construction), which project from the area behind the valve opening 12. Between the two legs 17 are two pins 18 (only one is visible), which form a fulcrum for the plate 9. At the other end of the plate 9, viewed from the tightening screw 15, an electromagnetic device 19 is located, which comprises an electromagnet 20, a spring 21 and a piston 22. The spring 21 presses the piston 22 against the plate 9 when the electromagnet 20 is switched off thereby opening the safety valve 6, fig 2. When the power is switched on, the electromagnet 20 pulls the piston 22 against the spring force of the spring 21 and the safety valve is closed by the spring 13, fig 3. Thus, the safety valve 6 is normally open, and closes only when the ventilator is in use. Apart from opening when the overpressure is too high, the safety valve 6 also opens at power failures and enables the patient to breath via the opening 12. By controlling the electromagnetic device 19 by the control unit, which receives information about pressure in the inspiration section 3 from the pressure transducer 5, the electromagnet 20 can be switched off at a pressure programmed in the control unit. A physician may hereby adapt the safety level of the pressure for each individual patient. In fig 4, an alternative embodiment of the safety valve 6 is shown. In this embodiment, the piston 22 is mechanically connected 25 to the plate 9, and the plate 9 is rotatably arranged around an axis of rotation 24. By regulating the current through the electromagnet 20, its pulling force on the piston 22 can be varied in order to correspond to the predetermined closing pressure of the safety valve and thereby there is no need for the springs 13. The overpressure at which the safety valve is to open can be selected in a simple manner and individually for each patient by means of a programmable control device 23 (which may be an integrated part of the control unit). To increase the safety of the ventilator in this embodiment, the current through the electromagnet 20 can be limited, so that the closing pressure never exceeds a predetermined maximum overpressure. Reference list 1 pneumatic unit 2 gas inlets 3 inspiration section 4 bacteria filter 5 pressure transducer 6 safety valve 7 expiration section 8 expiration valve 9 plate 10 adjustment plate 11 sealing disk 12 valve opening 13 springs 14 pins 15 tightening screw 16 indentations 17 legs 18 pins 19 electromagnetic device 20 electromagnet 21 spring 22 piston 23 programmable control device 24 axis of rotation 25 mechanical connection

Claims: Ventilator to be connected to the airways of a human being or an animal for supplying and emitting respiratory gas to and from the airways, respectively, which ventilator comprises an inspiration section (3) through which the respiratory gas is lead to the airways, which inspiration section (3) comprises at least one control valve for the gas flow and a safety valve (6), which is affected by a force load in the closing direction and a spring device (21, 22) in the opening direction, which safety valve (6) is located between the control valve and the airways, characterized in that; the safety valve (6) comprises a plate (9), arranged to be pivotable between an open position, in which the safety valve (6) is open, and a closed position, in which the safety valve (6) is closed; the spring device (21, 22) is arranged to affect the plate (9) in its opening direction; the force load is produced by at least one spring (13) connected to the plate (9) to affect the plate (9) in its closing direction; the force from the spring device (21, 22) exceeds the force from the spring (13); the spring constant is selected so that the force load corresponds to a predetermined overpressure in the inspiration section (3); and an electromagnet (20) is arranged to disconnect the effect of the spring device (21, 22) on the plate (9) when supplied with current, whereby the safety valve (6) is closed when the electromagnet (20) is connected and open when the electromagnet (20) is disconnected. Ventilator according to claim 1, characterized in that the safety valve (6) is provided with an adjustment device (15) for the spring (13). Ventilator according to claim 2, characterized in that the adjustment device (15) consists of a tightening screw for the spring (13). Ventilator according to any of the preceding claims, characterized in that a device (5) senses the pressure in the inspiration section (3) and in that the electromagnet (20) is disconnected at an overpressure that is lower than the predetermined overpressure Ventilator according to claim 4, characterized in that a programmable control device disconnects the electromagnet (20) at a programmed overpressure that is lower than the predetermined overpressure. Ventilator according to any of the claims 1 - 3, characterized in that a device (5) senses the pressure in the inspiration section (3) and in that the electromagnet (20) is disconnected at an overpressure that, by a predetermined safety interval, exceeds an adjustable overpressure that is lower than the predetermined overpressure. Ventilator to be connected to the airways of a human being or an animal for supplying and emitting respiratory gas to and from the airways, respectively, which ventilator comprises an inspiration section (3) through which the respiratory gas is lead to the airways, which inspiration section (3) comprises at least one control valve for the gas flow and a safety valve (6), which is affected by a force load in the closing direction and a spring device (21, 22) in the opening direction, which safety valve (6) is located between the control valve and the airways, characterized in that; the safety valve (6) comprises a plate (9), arranged to be pivotable between an open position, in which the safety valve (6) is open, and a closed position, in which the safety valve (6) is closed; the spring device (21, 22) is arranged to affect the plate (9) in its opening direction; the electromagnet (20) is attached to the plate (9) and the force load is produced by the pulling force of the electromagnet (20) when it is connected, whereby the force may be controlled by the current supply to the electromagnet (20) so that it corresponds to the force from the spring device (21, 22) plus a force corresponding to a predetermined overpressure in the inspiration section (3). Ventilator according to claim 7, characterized in that a device (5) senses the pressure in the inspiration section (3) and in that the electromagnet (20) is disconnected at an adjustable overpressure that is lower than the predetermined overpressure. Ventilator according to claim 8, characterized in that a programmable control device disconnects the electromagnet (20) at a programmed overpressure that is lower than the predetermined overpressure. Ventilator according to claim 7, characterized in that a device (5) senses the pressure in the inspiration section (3) and in that the electromagnet (20) is disconnected at an overpressure that, by a predetermined safety interval, exceeds an adjustable overpressure that is lower than the predetermined overpressure.

Inventors: DAHLSTROEM BO, ERIKSSON STURE, OLSSON SVEN-GUNNAR, PSAROS GEORGIOS, DAHLSTROEM, BO, ERIKSSON, STURE, OLSSON, SVEN-GUNNAR, PSAROS, GEORGIOS, Dahlström, Bo
Applicants: SIEMENS AG, SIEMENS ELEMA AB, SIEMENS AKTIENGESELLSCHAFT
Application year: 1991
Main classification: A61M16
IPC codes: A61M16