Exhalation valve assembly

An exhalation valve assembly for use in a volume ventilator circuit is disclosed. The valve assembly comprises a valve body defining a chamber with a gas inlet conduit and a gas outlet conduit, both in flow communication with the chamber. A diaphragm extends across the chamber and selectively closes off the gas inlet conduit. Upwardly extending strut members are disposed on an inside surface of the valve body and are used to position a removable ring member adjacent the diaphragm. The ring member is configured so as to support a portion of the diaphragm over the chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to respiratory therapy devices, and more 
particularly, to the design and construction of an exhalation valve 
assembly which can be modified for use in various volume ventilator 
circuits. 
2. Prior Art 
Volume ventilator circuits utilize an exhalation valve assembly to hold and 
maintain pressure within the circuit and selectively allowing gases to be 
exhaled by the patient and to escape therefrom. Such valve assemblies are 
comprised of a valve body and have a gas inlet conduit, which forms a gas 
discharge port within the valve body, and a gas outlet conduit. A flexible 
diaphragm selectively closes off the discharge port during inspiration. 
When the patient exhales, the diaphragm is pushed away from the port so as 
to allow the exhaled gases to escape from the valve body through the gas 
outlet conduit. 
The pressure holding capability of a volume ventilator circuit is dependent 
upon a number of factors including the ratio of the area of the diaphragm 
which extends across the chamber of the valve (hereinafter referred to as 
the "effective area") to the area of the gas discharge port. For ease of 
reference, the ratio of the effective area of the diaphragm to the area of 
the discharge port is referred to herein as the "valve area ratio." 
One of the most widely used volume ventilators in the respiratory therapy 
field has a limited capability for holding elevated Positive End 
Expiration Pressure ("P.E.E.P.") when using a circuit with a valve 
assembly having a valve area ratio usually below 1.5. The valve assembly 
used in such a circuit is specifically designed to achieve this ratio and 
cannot be modified so as to be used in another circuit requiring a 
different ratio. 
Another popular volume ventilator works on a somewhat different principal. 
This machine is not dependent upon the valve area ratio for high P.E.E.P. 
pressures, but is dependent on the valve area ratio for low patient 
exhalation effort beyond P.E.E.P. pressures. To achieve the required valve 
area ratio, the valve assembly is specifically designed and cannot be 
modified to provide a different valve area ratio for use in a different 
machine. 
Thus, prior art volume ventilators have required the use of specifically 
designed valve assemblies in order to achieve the desired valve area 
ratio. Notwithstanding the increased costs of manufacturing one specific 
valve for one type of machine and yet another valve for another type of 
machine, the prior art has been unable to provide any interchangeability 
of such valve assemblies. 
In other pressure circuits, the valves are also specifically designed for 
each circuit. An example of a prior art valve assembly for use in a 
pneumatic control system is shown in U.S. Pat. No. 3,633,605. This valve 
assembly employs a flexible diaphragm which selectively closes off one of 
two inlet ports. When the pressure from gas entering one inlet port is 
greater than that in the other inlet port, the diaphragm is pushed away 
from that port with the higher pressure, opening it to gas flow. The other 
port is occluded, thereby preventing gas flow. This valve assembly is 
designed such that there is no easy way to change the valve area ratio 
without constructing a whole new housing and diaphragm each having 
different dimensions. Because of this fact, such valve assembly cannot 
easily be used in a different system requiring a different valve area 
ratio. 
Yet another valve assembly is disclosed in U.S. Pat. No. 3,419,031. The 
valve shown in that patent also suffers from the above identified 
limitations. More specifically, such valve assembly includes a 
specifically designed resilient valve element which has dimensions related 
to the dimensions of the inlet and outlet conduits. As discussed 
hereinabove, it is not readily apparent how one could alter such assembly 
so as to use the valve in a different system. 
Thus, the prior art valve assemblies suffer from the shortcoming of using a 
specifically configured valve assembly. This leads to a proliferation of 
valve assemblies all fundamentally designed to perform the same function. 
The present invention overcomes these problems by providing a valve 
assembly which can be easily modified so as to achieve different valve 
area ratios. In this manner, one valve body can be made for use in 
different environments. The expense of constructing entirely different 
valve assemblies for use in different pressure circuits is thereby 
obviated. 
SUMMARY OF THE INVENTION 
It is one object of the present invention to provide an exhalation valve 
assembly with a simple, inexpensive means for changing the area ratio of 
the valve without entirely reconstructing such valve. 
Another object of this invention is to provide an exhalation valve assembly 
which can be used in different volume ventilator circuits. 
In general, the exhalation valve assembly of the present invention is 
designed for use in gas flow circuitry such as a volume ventilator 
circuit. The valve assembly includes a valve body having a chamber in flow 
communication with a gas inlet conduit and a gas outlet conduit. The gas 
inlet conduit is configured to be coupled to a patient connection such 
that exhaled gases from the patient are directed through a gas discharge 
port into a chamber formed in the valve body. The gas outlet conduit 
directs the exhaled gas out of the chamber. 
A diaphragm extends across the chamber formed in the valve body, and is 
configured to selectively close off the discharge port. The diaphragm is 
held in position by a removable cap which permits the easy replacement of 
the diaphragm with diaphragms of different configurations. 
Circumferentially disposed around the chamber on the internal wall of the 
valve body are a plurality of upwardly extending strut members. These 
strut members are used to support a ring member which supports a portion 
of the diaphragm from extending across the chamber. This reduces the 
effective area of the diaphragm. Accordingly, when the ring member is 
used, the ratio of the effective area of the diaphragm to the area of the 
discharge port is decreased. 
By the use of the valve assembly of the present invention, the valve area 
ratio can easily be modified so as to meet the needs of the specific 
circuit in which the assembly is to be used. More specifically, one need 
merely remove the cap from the assembly, remove the diaphragm and ring 
member, and insert a different diaphragm or diaphragm/ring combination. 
The cap is then replaced and the assembly is now ready to be used. 
The operation of the valve assembly in any configuration basically is the 
same. During inspiration, the diaphragm closes off the discharge port thus 
preventing any gas from traveling through the valve assembly. This action 
is achieved by the application of positive pressure over the diaphragm as 
more fully discussed herein. Upon exhalation, the exhaled gas travels 
through the inlet conduit. The pressure exerted by the gas forces the 
diaphragm to disengage from the discharge port thereby allowing the 
exhaled gas to enter the body of the valve where it is directed out of the 
valve body through the outlet conduit. If a ring member is being used, the 
pressure needed to disengage the diaphragm from the discharge port is less 
than if a diaphragm is used without a ring member. This is because the 
ring member supports a portion of the diaphragm thus reducing its 
effective area. The valve area ratio (effective area of the 
diaphragm--area of discharge port) is greater without the ring member than 
with the ring member. Thus, by using a specific diaphragm and ring 
combination or omitting the ring member, the valve assembly can be 
modified so as to meet the specific valve area ratio needs of a given 
volume ventilator circuit. 
The novel features which are believed to be characteristic of the 
invention, both as to its organization and method of operation, together 
with further objectives and advantages thereof, will be better understood 
from the following description considered in connection with the 
accompanying drawings in which a presently preferred embodiment of the 
invention is illustrated by way of example. It is to be expressly 
understood, however, that the drawings are for the purpose of illustration 
and description only, and are not intended as a definition of the limits 
of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
1. The Device 
Referring first to FIG. 1, the valve assembly 10 of the present invention 
is shown. The valve assembly 10 is comprised of a valve body 12 forming a 
generally circular housing 14 defining a chamber 16. An inlet conduit 18 
and an outlet conduit 20 are in flow communication with chamber 16. 
Disposed on the inside wall of the valve body 12 are a plurality of 
upwardly extending support members or struts 28. As is hereinafter 
discussed, such support members 28 are used to position a ring member 
inside the housing 14. Also disposed on the valve body 12, adjacent the 
bottom thereof, is an outwardly extending and generally rectangular 
mounting support member 22. Such mounting support member 22 enables the 
valve assembly 10 to be attached to a support structure (not shown) and 
thereby held in a predetermined position. 
One end of the inlet conduit 18 includes a section 26 which extends into 
the chamber 16 and forms a circular gas discharge port 24. In the 
preferred embodiment, port 24 is circumferentially disposed in chamber 16. 
The other end of the inlet conduit 18 as well as the outlet conduit 20 
each have specifically configured coupling ends 30 as are well known in 
the art. Such ends 30 enable the conduits to be readily joined to flexible 
tubing (not shown) or to other elements in a volume ventilator circuit. 
The valve assembly 10 also includes a flexible, circular diaphragm member 
32 which is disposed across the chamber 16. A cap or cover 34 snap locks 
onto the body 12 as hereinafter described and holds the diaphragm 32 
across the chamber 16. Centrally located on the cover 34 is a gas inlet 
port 36 which can be used to direct a gas into the assembly 10. Note, 
however, that in the preferred embodiment, gas from part 36 does not flow 
into chamber 36, but only into the area above diaphragm 32. In this 
manner, the pressure above the diaphragm 32 can be regulated. 
In the first embodiment of the present invention, a circular, plastic ring 
member 38 is disposed in the valve body 12 and rests on the support 
members 28. This is illustrated in FIGS. 1 and 3. In the preferred 
embodiment, ring member 38 is disposed in the body 12 adjacent the 
periphery of chamber 16 and circumferentially surrounds the gas discharge 
port 24. It is to be understood, however, that other means for supporting 
ring member 38 in the valve body 12 are within the scope of this 
invention. Once the ring member 38 is in position, the diaphragm 32 is 
then placed over it. The diaphragm 32 includes an upwardly extending 
section 54 configured to arch over the ring member 38, and a generally 
circular section 56 which is used to selectively close off the gas 
discharge port 24. The diaphragm 32 rests on a grooved area 46 formed by 
an inner wall 42 and an outer wall 44 on the valve body 12. When the cover 
34 is disposed over the diaphragm 32, as is more clearly shown in FIG. 3, 
it snap locks over lip 40. More specifically, a rim 52 on cover 34 snap 
locks over the lip 40 and is held in position by outwardly extending tab 
members 48 formed on the periphery of the lip 40. A circular ledge 50 
formed on an inside surface of the cover 34 presses the diaphragm 32 into 
the groove 46. This holds the diaphragm 32 in position. It is to be 
understood, however, that other means for holding the diaphragm 32 in 
position are within the scope of the invention. 
Again referring to FIG. 3, one can see that ring member 38 supports a 
portion of the diaphragm 32 thereby occluding such portion of the 
diaphragm 32 from extending across the chamber 16. Thus, the effective 
area of the diaphragm 32 over the chamber 16 is decreased thereby 
decreasing the valve area ratio. In turn, less pressure is required to 
raise the diaphragm 32 off of the gas discharge port 24. 
A second embodiment of the present invention will now be discussed with 
reference to FIGS. 2 and 4. In the second embodiment, the ring member 38 
has been removed and a circular diaphragm 32A of slightly different 
configuration than diaphragm 32 is inserted into the valve body 12. In the 
second embodiment, with the ring member 38 removed, the diaphragm 32A is 
configured so as to have a generally downwardly extending section 58 and a 
circular section 60 which is disposed above and adjacent to the discharge 
port 24. Section 60 acts to close off discharge port 24 in the same manner 
as section 56 of the first diaphragm 32. All the other elements of the 
valve body 12 in the second embodiment remain the same. 
2. Operation of the Valve Assembly 
The operation of the valve assembly 10 of the present invention will now be 
discussed. In operating the valve assembly 10 in one manner, a patient 
connection hose (not shown) is joined to the gas inlet conduit 18 and 
secured thereto by means of the coupling end 30. Likewise, an outlet hose 
(not shown) is joined to the gas outlet conduit 20 and secured thereto by 
coupling end 30. During inspiration, it is necessary to maintain a 
positive pressure above diaphragm 32. Therefore, a gas supply tube is 
joined to the gas inlet port 36 on the cover 34 such that a gas is 
directed into the assembly 10 above the diaphragm 32 or 32A. This enables 
a positive pressure to be created above the diaphragm. During exhalation, 
it is sometimes desirable to maintain a positive pressure above the 
diaphragm, thus forcing the patient to exert an elevated pressure in order 
to exhale past the diaphragm. The elevated pressure exerted is determined 
by the air pressure applied above the diaphragm and the valve area ratio. 
It is to be understood, however, that in other applications, it may be 
desirable not to maintain such positive pressure. In that case, no 
pressure would be maintained above diaphragm during exhalation. 
Referring now to FIG. 3, one can see arrows 70 which generally indicate the 
flow of gas for example, exhaled gas from a patient, as it would be 
directed through the assembly 10 in the first embodiment of the present 
invention. More specifically, when the patient exhales with sufficient 
pressure, the pressure above the diaphragm 38 (positive pressure supplied 
by a gas source or atmospheric) is overcome. This causes the diaphragm 32 
to disengage port 24. The exhaled gas then flows through the inlet conduit 
18, through gas discharge port 24 and into the chamber 16. The exhaled gas 
would flow out of the chamber 16 through the outlet conduit 20. During 
inspiration a positive pressure is created in the assembly 10 above 
diaphragm 32 causing section 56 of the diaphragm 32 to engage port 24. 
This prevents gas from escaping from the patient circuit through the valve 
assembly 10. Air or other gas to the patient comes from the ventilator, 
connected to patient circuit upstream from valve assembly 10. 
As discussed hereinabove, prior art ventilator circuits were designed such 
that specific amounts of pressure were required in order to cause the 
diaphragm 32 to disengage the discharge port 24 thereby permitting escape 
of the exhaled gas. The present invention enables this to take place, and 
further enables such pressure to be regulated by the use of a specifically 
designed ring member and diaphragm. Ring member 38 extends towards the 
center of the chamber 16 and in one embodiment supports a portion of the 
diaphragm 32. Because ring 38 acts as a support for a section of the 
diaphragm 32, the amount of force necessary to disengage the diaphragm 32 
from the discharge port 24 is decreased. If one desired to increase the 
force necessary to disengage the diaphragm 32 from the port 24, the ring 
member 38 could be removed and/or a different diaphragm or ring used. For 
example, in the second embodiment the pressure necessary to disengage the 
diaphragm from the port 24 is increased by interchanging diaphragm 32 with 
diaphragm 32A and by removing the ring member 38 from the assembly 10. 
Diaphragm 32A is not supported by any ring member and therefore a larger 
effective area is presented. This larger effective area necessitates the 
use of more pressure in order to disengage the diaphragm 32A from the 
discharge port 24. It has been found that by using diaphragm 32 and ring 
member 38, the valve area ratio is approximately 1:1 although 
modifications in the ring 38 or diaphragm 32 can lead to a valve area 
ratio between 1:1 and 2:1. Using diaphragm 32A without any ring member 
yields a valve area ratio of approximately 2:1. Other valve area ratios 
greater than 2:1 are also within the scope of the present invention. 
Thus, the present invention provides a solution whereby one valve body may 
be produced and used in a variety of pressure circuits. If one desires to 
change the effective area ratio of the valve assembly 10, the cover 34 can 
easily be removed from the body 10 by merely snapping the cover 34 off the 
lip 40 and by removing the diaphragm 32 as well as the ring member 38. 
Another diaphragm, for example, diaphragm 32A, can then be inserted and 
the cover 34 again snapped on to the valve body 12. The assembly 10 is now 
ready for use in a different circuit requiring a different valve area 
ratio. 
A wide variety of materials, shapes and other configurations can be used in 
this invention. It should therefore be understood that changes can be made 
without departing from the overall scope or spirit. For example, in the 
preferred embodiment all of the parts of the present invention are made 
out of plastic material such as nylon, PVC, acrylic resins and the like. 
Of course, other materials such as reinforced plastics or even metals are 
within the scope of the present invention. Further, the shape of the 
diaphragm and the ring member can be modified so as to achieve various 
valve area ratios. This invention, therefore, is not to be limited to the 
specific embodiments discussed and illustrated herein.