GB1604871A

GB1604871A - Expiration valve

Info

Publication number: GB1604871A
Application number: GB552378A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-02-10
Filing date: 1978-02-10
Publication date: 1981-12-16
Also published as: FR2417047A1; SE7812143L; DE2851192A1; FR2417047B1; DE2851192C2; JPS54108497A; SE434702B

Description

(54) EXPIRATION VALVE (71) I, RUTH LEA HESSE, a Danish Citizen, of Piniehj 23, DK-2960, Rungsted Kyst, Denmark, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention concerns an expiration valve of such construction that, when connected to the expiratory outlet of apparatus for artificial positive pressure ventilation of a patient's lungs, the valve permits the setting up of a positive pressure that is retained in the patient's lungs when expiration has terminated.

This form of artificial ventilation of a patient's lungs, where the patient expires to a controlled positive pressure level and not to the atmospheric pressure, is known as "PEEP" ventilation, an abbreviation of Positive End-Expiratory Pressure ventilation.

Various kinds of so-called "PEEP" valves that permit such ventilation to be carried out are known.

The simplest kind of PEEP valve consists of a flexible tube, one end of which is attached to the expiratory outlet of the apparatus, the other end being immersed in water or other fluid, so that air expired by a patient has to displace the water column present in the tube in order to escape and rise to the surface of the water in order to escape and rise to the surface of the water in the form of bubbles. The end-expiratory pressure thus becomes equal to the depth to which the tube is immersed in the water.

Such an arrangement is, however, only suitable for use in conditions in which a receptacle for the fluid can be firmly supported and kept steady.

" Other arrangements are known in which the expiratory outlet of ventilating apparatus is connected to a valve opening leading to a valve seat covered by a diaphragm, the downstream side of which is loaded by an adjustable pneumatic pressure, so that expiration via the valve can only occur as long as the expiratory pressure is capable of lifting the diaphragm free of the valve seat against the downstream pneumatic pressure.

Such valve arrangements can, however, only be used in circumstances in which an accurately controllable and adjustable source of pneumatic pressure is available for loading the diaphragm, e.g. from the control system of a respirator.

Furthermore, spring-loaded PEEP valves are known, such valves comprising an inlet adapted for connection to the expiratory outlet of ventilation apparatus and leading to a valve seat which is covered on its downstream side by a spring-loaded valve disc, so that expiration only takes place via such valves if the expiratory pressure is capable of opening the valve against the spring force acting on the valve disc.

Spring-loaded PEEP valves have the advantage of being compact and usable without requiring pneumatic pressure or fluid receptacle. However, known designs have had the disadvantage that they tend to vibrate during expiration, reducing the accuracy of the valve's setting capability and producing an unacceptably high noise level.

The present invention thus seeks to prevent, or at least reduce, the occurrence of undesirable vibration associated with expiration valves.

Accordingly one aspect of the present invention provides an expiration valve comprising a valve housing having an inlet for connection to the expiratory outlet of ventilating apparatus and an outlet, a valve seat disposed within the housing, a valve disc biased in an upstream direction to engage said valve seat, a damping chamber containing a viscous fluid disposed within the valve disc, and a valve rod that is supported in the housing and extends into the damping chamber and is provided with a flange that is arranged to abut respective stop surfaces within the damping chamber at respective extremes of movement of the valve disc with respect to the valve rod, the damping chamber being arranged such that movement of the valve disc within the housing causes movement of the viscous fluid within the damping chamber, acting to damp vibration.

In a preferred embodiment of the invention the valve rod is fixedly secured within the valve housing and extends through a bore in the valve disc between the upstream and downstream sides thereof, and a pair of flexible annular diaphragms extend between the valve rod and the valve disc to define in part said damping chamber.

The valve disc may thus be floatingly supported by the membranes.

A second aspect of the invention provides an expiration valve comprising a valve housing having an inlet for connection to the expiratory outlet of ventilating apparatus and an outlet, a valve seat disposed within the housing, a valve disc biased in an upstream direction to engage the valve seat, a valve rod fixedly supported in the housing and extending through a bore in the valve disc between the upstream and downstream sides thereof, and having a flange that is arranged to abut the stop surfaces within the bore to limit axial movement of the valve disc with respect to the valve rod, and a pair of flexible annular diaphragms extending between the valve rod and the valve disc to define a damping chamber containing a viscous fluid the damping chamber being arranged so that movement of the valve disc within the housing causes movement of the viscous fluid within the damping chamber, acting to damp vibrations by way of example with reference to the accompanying drawing that is a longitudinal section through an expiration valve.

The illustrated expiration valve consists of a two-part, substantially circular cylindrical valve housing 1 that is divided into two chambers by means of an annular partition 2. A first, inlet chamber la includes an opening 3 adapted for airtight connection to the expiratory outlet of an apparatus for artificial positive pressure ventilation of a patient's lungs, and a.second, outlet chamber lb communicates with the atmosphere via openings 4 in the wall of the valve housing 1.

The inner edge of the partition 2 is formed to provide a circular valve seat 13 disposed on the downstream side of partition 2 and engaged by a valve disc 30 that is urged against seat 13 by the action of a coil spring 5 disposed within chamber lb. The spring 5 is so placed that one end of the spring rests on the valve disc 30 and the other end seats on mobile means 6 that is adjustably retained in position by a threaded cap 7 that is screwed onto an end portion of the housing and is thus movable in the direction of the spring's longitudinal axis, so that the spring force acting on the valve disc 30 can be adjusted by turning said threaded cap 7.

The valve disc 30 comprises a circular, easily flexible annular diaphragm ring 8 of rubber or similar elastic material that forms the circumference of the valve disc and that is capable of completely sealing the opening in the partition 2 in response to even light pressure on the downstream side. An outwardly extending flange 9 of a support member 31 made of lightweight, rigid material, e.g. suitable plastics materials, is secured to the internal circumference of ring 8. The support member 31 further comprises a central hub portion 10 that extends axially in the interior of the pre-strained spring 5, which seats on the downstream side of the flange 9. The hub portion 10 has an internal boring 11 that extends centrally throughout the support member 31.

A valve rod 12 is fixedly secured within the valve housing, aligned with the longitudinal axis of the housing and extending through boring 11 and thus at right angles to the disc seat 13. A small disc 14 is fixed to the rod 12 at a location within bore 11, to define a flange on the rod, and is arranged to limit the axial movement of the valve disc 30 in relation to the rod 12 and thus the valve housing 1. To this end, two parts 15 are secured by means of a snap fit within the boring 11, suitable grooves 16 adapted to receive corresponding projections of parts 15 being provided within boring 11. As shown in the drawing, the parts 15 each include an inwardly projecting portion 17 that encircles rod 12 with a fairly large radial clearance. The portions 17 are so positioned as to define an annular recess within which is disposed disc 14, appropriate surfaces of projecting portions 17 constituting abutment surfaces that act to abut disc 14 and thus limit the axial movement of valve disc 30 with respect to disc 14 and hence with respect to housing 1.

Two thin-walled, elastic annular diaphragms 18 made of soft rubber and preferably being conically shaped to permit easy axial movement extend between the axial extremities of parts 15 and the rod 12. Thus, the valve disc is floatingly supported by the membranes 18. The inner edge of each diaphragm 18 is reinforced by a rim 19 that fits tightly around the rod 12. The external circumference of each diaphragm 18 is supplied with a sealing rim 20 that is fitted in a recess in part 15, thus wedging the outer edge of the diaphragm 18 between the boring 11 and the part 15.

A labyrinth, or damping, chamber 32 is thus defined by the rod 12 with disc 14, the two diaphragms 18 and the parts 15 and is filled with a fluid 21 of high viscosity e.g.

silicone oil, which flows within the labyrinth chamber 32 when the valve disc 30 moves in relation to the fixed valve rod 12.

The above described design of the valve disc 30 for a spring-loaded PEEP valve allows an expert easily to coordinate the flow path of the labyrinth chamber 32 and the viscosity of the confined fluid 21 so that a critical damping is obtained of the vibratory system composed of the prestrained spring 5, the valve disc 30 and the volume of com pressed air present, during expiration, between the patient's airways and the valve disc 30.

When the above described valve is connected by means of opening 3 to the expiratory outlet of ventilating apparatus, and a patient expires via the valve, the valve disc 30 will be lifted off its seat 13, thus allowing a through flow of exhaled air to the ambient atmosphere, when the patient exerts an expiratory pressure sufficient to overcome the spring force acting on the downstream side of the valve disc 30. Because the damping chamber 32 inside the valve disc 30 provides a damping action by means of a viscous fluid, no damping force will result when the valve disc 30 remains stationary in relation to the fixed valve rod 12. Only when the valve disc 30 is mobile will a reactive force be set up resulting from the pressure loss caused by the fluid flowing in the labyrinth chamber 32, and the direction of this force will always be opposed to that of the valve disc's instantaneous direction of movement. Thus, when expiration begins, movement of the valve disc 30 will start at a pressure determined solely by the spring force and the area of the valve disc. During the subsequent opening movement, the spring force plus a contribution from the damping device act against the pressure exerted by the expired air on the valve disc 30. When this opening movement ceases, the spring force and the expiratory pressure toward the valve disc will again solely determine the position of the disc 30 in relation to the valve seat 13. Should the pressure of the expired air fall as a result of pressure vibrations in the air or decreasing expiratory velocity, the spring force will cause the valve disc 30 to move toward the valve seat 13, whereby the damping device will create a force acting in the opposite direction to the spring force, which in turn will counteract the acceleration of the valve disc 30 towards the seat 13. When the damping device as described is attuned to critical damping, it will not be possible for the valve disc 30 to set up resonance vibrations by these movements, and the opening and closing pressure of the valve will be determined solely by the adjustable spring force setting.

WHAT I CLAIM IS: 1. An expiration comprising a valve housing having an inlet for connection to the expiratory outlet of ventilating apparatus and an outlet, a valve seat disposed within the housing, a valve disc biased in an upstream direction to engage said valve seat, a damping chamber containing a viscous fluid diposed within the valve disc, and a valve rod that is supported in the housing and extends into the damping chamber and is provided with a flange that is arranged to abut respective stop surfaces with the damping chamber at the respective extremes of movement of the valve disc with respect to the valve rod, the damping chamber being arranged such that movement of the valve disc within the housing causes movement of the viscous fluid within the damping chamber, acting to damp vibration.

2. An expiration valve according to Claim 1 in which the valve rod is fixedly secured within the valve housing and extends through a bore in the valve disc between the upstream and downstream sides thereof, and a pair of flexible annular diaphragms extend between the valve rod and the valve disc to define in part said damping chamber.

3. An expiration valve comprising a valve housing having an inlet for connection to the expiratory outlet of ventilating apparatus and an outlet, a valve seat disposed within the housing, a valve disc biased in an upstream direction to engage the valve seat, a valve rod fixedly supported in the housing and extending through a bore in the valve disc between the upstream and downstream sides thereof, and having a flange that is arranged to abut stop surface within the bore to limit axial movement of the valve disc with respect to the valve rod, and a pair of flexible annular diaphragms extending between the valve rod and the valve disc to define a damping chamber containing a viscous fluid, the damping chamber being arranged so that movement of the valve disc within the housing causes movement of the viscous fluid within the damping chamber, acting to damp vibrations.

4. An expiration valve according to Claim 2 or Claim 3 wherein said diaphragms are of soft rubber and of conical shape.

5. An expiration valve according to any one of Claims 2, 3 or 4 in which the valve disc is floatingly supported by the membranes.

6. An expiration valve according to any one of the preceding claims in which the flange comprises a rigid disc secured to the valve rod.

7. An expiration valve according to any one of the preceding claims, wherein the viscous fluid comprises silicone oil.

8. An expiration valve according to any one of the preceding claims, wherein the valve disc is biased by means of a compression spring acting on the downstream side thereof.

9. An expiration valve according to claim 7, including a screw threaded cap adjustably secured to the housing and on which said compression spring rests.

10. An expiration valve according to any one of the preceding claims, wherein the valve disc comprises a rigid support member secured to the inner edge of a flexible

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pressed air present, during expiration, between the patient's airways and the valve disc 30. When the above described valve is connected by means of opening 3 to the expiratory outlet of ventilating apparatus, and a patient expires via the valve, the valve disc 30 will be lifted off its seat 13, thus allowing a through flow of exhaled air to the ambient atmosphere, when the patient exerts an expiratory pressure sufficient to overcome the spring force acting on the downstream side of the valve disc 30. Because the damping chamber 32 inside the valve disc 30 provides a damping action by means of a viscous fluid, no damping force will result when the valve disc 30 remains stationary in relation to the fixed valve rod 12. Only when the valve disc 30 is mobile will a reactive force be set up resulting from the pressure loss caused by the fluid flowing in the labyrinth chamber 32, and the direction of this force will always be opposed to that of the valve disc's instantaneous direction of movement. Thus, when expiration begins, movement of the valve disc 30 will start at a pressure determined solely by the spring force and the area of the valve disc. During the subsequent opening movement, the spring force plus a contribution from the damping device act against the pressure exerted by the expired air on the valve disc 30. When this opening movement ceases, the spring force and the expiratory pressure toward the valve disc will again solely determine the position of the disc 30 in relation to the valve seat 13. Should the pressure of the expired air fall as a result of pressure vibrations in the air or decreasing expiratory velocity, the spring force will cause the valve disc 30 to move toward the valve seat 13, whereby the damping device will create a force acting in the opposite direction to the spring force, which in turn will counteract the acceleration of the valve disc 30 towards the seat 13. When the damping device as described is attuned to critical damping, it will not be possible for the valve disc 30 to set up resonance vibrations by these movements, and the opening and closing pressure of the valve will be determined solely by the adjustable spring force setting. WHAT I CLAIM IS:

1. An expiration comprising a valve housing having an inlet for connection to the expiratory outlet of ventilating apparatus and an outlet, a valve seat disposed within the housing, a valve disc biased in an upstream direction to engage said valve seat, a damping chamber containing a viscous fluid diposed within the valve disc, and a valve rod that is supported in the housing and extends into the damping chamber and is provided with a flange that is arranged to abut respective stop surfaces with the damping chamber at the respective extremes of movement of the valve disc with respect to the valve rod, the damping chamber being arranged such that movement of the valve disc within the housing causes movement of the viscous fluid within the damping chamber, acting to damp vibration.

annular diaphragm arranged to engage the valve seat.

11. An expiration valve substantially as described with reference to, and as shown in, the accompanying drawing.