Pumps – Condition responsive control of pump drive motor – Single motor control element responsive to means sensing...
Reexamination Certificate
1999-09-03
2001-10-02
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Single motor control element responsive to means sensing...
C417S036000, 60
Reexamination Certificate
active
06296450
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems and methods for processing and collecting blood, blood constituents, or other suspensions of cellular material.
BACKGROUND OF THE INVENTION
Today people routinely separate whole blood, usually by centrifugation, into its various therapeutic components, such as red blood cells, platelets, and plasma.
Conventional blood processing methods use durable centrifuge equipment in association with single use, sterile processing systems, typically made of plastic. The operator loads the disposable systems upon the centrifuge before processing and removes them afterwards.
Conventional blood centrifuges are of a size that does not permit easy transport between collection sites. Furthermore, loading and unloading operations can sometimes be time consuming and tedious.
In addition, a need exists for further improved systems and methods for collecting blood components in a way that lends itself to use in high volume, on line blood collection environments, where higher yields of critically needed cellular blood components, like plasma, red blood cells, and platelets, can be realized in reasonable short processing times.
The operational and performance demands upon such fluid processing systems become more complex and sophisticated, even as the demand for smaller and more portable systems intensifies. The need therefore exists for automated blood processing controllers that can gather and generate more detailed information and control signals to aid the operator in maximizing processing and separation efficiencies.
SUMMARY OF THE INVENTION
The invention provides systems and methods for processing blood and blood constituents that lend themselves to portable, flexible processing platforms equipped with straightforward and accurate control functions.
More particularly, the invention provides various systems and related methods for pumping fluid through a pump having a known stroke volume. The systems and methods employ gravimetric control measures to monitor fluid flow through the pump. The systems and methods include an actuator, which interacts with the pump during a stroke interval (T
Stroke
) to pump fluid through the pump. The systems and methods couple a receptacle to the pump, to either dispense fluid into the pump or to receive fluid from the pump.
According to one aspect of the invention, the systems and methods detect changes in weight of the receptacle over a sample time period. The systems and methods achieve a desired flow rate (Q
Desired
) by deriving an actual flow rate (Q
Actual
) by sensing changes in weight of the receptacle over the sample time period, taking into account the density of the fluid, and adjusting the stroke interval based upon Q
Actual
so that Q
Desired
is achieved. In one embodiment, in operating the actuator, the stroke interval T
Stroke
comprises a time interval component to draw fluid into the pump (T
1
), a time interval component to expel the fluid from the pump (T
2
), and an idle time interval component (T
3
). In this embodiment, in controlling the pump, one or more of the time interval components T
1
, or T
2
, or T
3
is adjusted to a new magnitude to achieve Q
Desired
, according to the following relationship:
T
n
(
Adjusted
)
=
k
(
SV
Q
Desired
)
-
T
n
(
NotAdjusted
)
where:
T
n(Adjusted)
is the magnitude of the time interval component or components after adjustment to achieve the desired flow rate Q
Desired
.
T
n(NotAdjusted)
is the magnitude of the value of the other time interval component or components of T
Stroke
that are not adjusted, wherein the adjusted stroke interval after adjustment to achieve the desired flow rate Q
Desired
is the sum of T
n(Adjusted)
and T
n(NotAdjusted)
.
k is a correction factor that accounts for interactions between the pump and the upstream and downstream pressures, expressed as follows:
k
=
T
Stroke
×
(
Q
Actual
SV
)
According to another aspect of the invention, the systems and methods detect changes in weight of the receptacle over a sample time period, and detect abnormal operating conditions based upon a pump correction factor k, which accounts for interactions between the pump and the upstream and downstream pressures. The systems and methods generate an alarm output based upon the pump correction factor k. The pump correction factor k is derived as follows:
k
=
T
Stroke
×
(
Q
Actual
SV
)
The criteria for generating the alarm output can vary. For example, the alarm output can be generated based upon deviance between magnitude of k and an expected value. Alternatively, or in combination, the alarm output can be generated based upon deviance between polarity of k and an expected polarity. In one embodiment, the systems and methods also detect changes in weight of the receptacle when the actuator is not operating and generate an alarm output.
In an embodiment incorporating one or more aspects of the invention, pump includes a pump chamber having the essentially constant volume.
In an embodiment incorporating one or more aspects of the invention, the pump is coupled to a blood separation device, as part of a blood processing system.
In an embodiment incorporating one or more aspects of the invention, the systems and methods provide a cassette, which contains a pneumatically actuated pump station comprising a pump chamber having a known stroke volume. The systems and methods include a pneumatic actuator to hold the cassette and selectively apply pneumatic force to the pump chamber during the stroke interval to pump fluid through the pump chamber.
Other features and advantages of the inventions are set forth in the following specification and attached drawings.
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Brown Richard I
Mullen Richard E
Westberg Tom
Yu Clement Lim
Baxter International Inc.
Freay Charles G.
Price Bradford R. L.
Rockwell Amy L. H.
Ryan Daniel D.
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