Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
1999-02-22
2001-06-26
Rivell, John (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S247110, C137S248000, C137S519000, C137S859000
Reexamination Certificate
active
06250331
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to shed blood recovery systems, and more specifically, to a zero crack-pressure, high-flow valve especially suited for such systems.
BACKGROUND OF THE INVENTION
During surgical operations, patients often lose a significant amount of blood. To avoid serious complications, this blood volume is often replaced. In particular, whole blood or a blood component is transfused into the patient. To maintain adequate supplies of blood and blood components, many hospitals and blood banks rely on donors who are typically un-related to the transfusion recipients. Despite rigorous testing protocols, there remains some risk of transmitting blood-borne diseases during transfusions. Thus, it is desirable to limit or even avoid, if possible, transfusions of donated blood. One way of reducing the reliance on donated blood is to collect the patient's own blood that is shed during surgery. This blood may then be processed by a blood recovery system and re-infused into the patient. By salvaging a patient's own blood, one can limit the amount of donated blood that the patient must receive, thereby reducing the risk of exposure to blood-borne diseases.
U.S. Pat. No. 5,634,893, for example, is directed to an autotransfusion system that recovers shed blood.
FIG. 1
is a block diagram of the '893 system
10
. The system
10
includes a compound reservoir
12
having upper
16
and lower
14
chambers that are interconnected by a drain valve
18
. A suction tube
22
connects a wound or surgical site to the upper chamber
16
which is also connected to a vacuum source
32
. A selector valve
38
selectively couples the lower chamber
14
to the vacuum source
32
or to atmospheric pressure. Normally, the valve
38
is positioned so that the vacuum is applied equally to both chambers
14
,
16
. That is, the absolute pressure in both chambers
14
,
16
is the same. Accordingly, blood from the surgical site is drawn through suction tube
22
and into the upper chamber
16
. The blood first flows through a particle filter
20
located in the upper chamber
16
to remove debris, such as blood clots, bone chips, etc. The filtered blood then collects in the upper chamber
16
. A lipid (i.e., liquid oils) separation system
61
is also located in the upper chamber
16
. The lipid separator
61
includes a partition
60
having an opening
60
a
, a dam
64
and moat
62
that are formed around the drain valve
18
and cooperate to block lipids from flowing through the drain valve
18
and entering the lower chamber
14
. Thus, the shed blood that drains into the lower chamber
14
is substantially free of particles and lipids.
The drain valve
18
located between the two chambers
14
,
16
is a conventional, vacuum-operated, duckbill-type drain valve. That is, drain valve
18
includes a pair of opposing lips
80
a
,
80
b
that are formed from a flexible or elastomeric material. The two lips
80
a
,
80
b
are normally sealed at their outer ends
82
a
,
82
b
but may be opened to define an aperture. That is, the ends
82
a
,
82
b
of the two opposing lips
80
a
,
80
b
are normally in contact with each other, thereby blocking the flow of fluid between the two chambers
14
,
16
. When a sufficient volume of filtered, lipid-reduced blood builds-up within the drain valve
18
, the corresponding fluid pressure exerted on the inside of the flexible lips
80
a
,
80
b
causes them to open and allow the blood to flow through the aperture defined thereby and enter the lower chamber
14
.
When the lower chamber
14
is full of blood or contains a sufficient volume for reinfusion, the selector valve
38
is moved to the second position, thereby venting the lower chamber
14
to atmospheric pressure. The upper chamber
16
nonetheless remains at vacuum pressure. The pressure differential between the two chambers
14
,
16
causes the two lips
80
a
,
80
b
of the drain valve
18
to close together, stopping the flow of blood between the two chambers
14
,
16
, and also preventing vacuum loss in upper chamber
14
. The blood in the lower chamber
16
may then be drained to a blood bag
76
for subsequent transfusion. Once the lower chamber
16
has been emptied, the blood bag
76
is sealed-off by a clamp
74
and the selector valve
38
is returned to the first position, allowing filtered, lipid-reduced blood to drain into the lower chamber
14
, as described above.
As shown, the '893 system allows processed, recovered blood to be transferred to a blood bag without interrupting the suction being applied to the surgical site. Thus, the '893 system efficiently salvages shed blood without disrupting the drainage of surgical sites. It has been discovered, however, that the duckbill-type drain valve has several disadvantages. First, as described above, the valve is normally in a closed position. That is, the two opposing lips are normally in contact at their outer ends and are only opened in response to fluid pressure exerted by a volume of blood inside the valve. The valve, moreover, is formed from bio-compatible silicone whose physical properties, unlike certain metals and hard plastics, can vary greatly, even if the silicone is manufactured by the same supplier under generally the same conditions. Accordingly, the fluid pressure required to “crack” or break open the prior art valve can vary significantly from one valve to the next. In some instances, the crack pressure may actually exceed the fluid pressure that can practically be generated within the blood recovery system (e.g., the column of blood necessary to open the valve exceeds the height of the upper chamber). This lack of predictability in the crack pressure of the prior art valve raises significant quality assurance issues.
Additionally, sterilization of the '893 system can result in the valve becoming sealed, effectively preventing it from opening at all. More specifically, during sterilization, the '893 blood recovery system, including the duckbill valve, is typically heated to approximately 60° C. At this temperature, the surface of silicone components often becomes “tacky”. If two of these “tacky” surfaces are brought into contact with each other, they can adhere to one another. Since the conventional duckbill valve has two silicone lips that are in contact with each other, sterilization can cause the two surfaces to adhere to each other, significantly increasing the force needed to open the valve. Indeed, the volume of fluid required to open the valve may actually exceed the capabilities of the '893 system. Sterilization can thus render the conventional valve inoperable.
Accordingly, a need has arisen for a new valve assembly that preferably opens at zero fluid pressure (e.g., a zero crack-pressure valve), but provides a relatively high fluid flowrate. It is an object of the present invention to provide a valve assembly having zero crack pressure and a high flowrate. It is a further object of the present invention to provide a valve that does not degrade or become inoperable following sterilization. Another object of the present invention is provide a valve that reliably and predictably opens and closes. A further object of the present invention is to provide a valve that closes in response to slight pressure differentials across the valve.
SUMMARY OF THE INVENTION
Briefly, the present invention relates to a zero crack-pressure, high-flow valve assembly especially suited for use with blood salvage or recovery systems. The valve assembly cooperates with a valve seat defining an opening for selectively providing fluid communication between two adjacent chambers based on the pressure differential between the chambers. The valve assembly includes a disk that is slightly larger than the opening in the valve seat. One or more flexible or elastic arms connect the disk to a concentric ring support permitting the disk to move relative to the ring support in a direction that is generally perpendicular to the nominal plane of the ring support. The connecting arms also define f
Cesari & McKenna LLP
Haemonetics Corp.
Krishnamurthy Ramesh
Rivell John
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