U.S. patent application number 12/020498 was filed with the patent office on 2009-07-30 for two chamber pumps and related methods.
This patent application is currently assigned to Phluid,Inc.. Invention is credited to Paul Mario DiPerna.
Application Number | 20090191067 12/020498 |
Document ID | / |
Family ID | 40899426 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191067 |
Kind Code |
A1 |
DiPerna; Paul Mario |
July 30, 2009 |
TWO CHAMBER PUMPS AND RELATED METHODS
Abstract
Two chamber pumps and related methods provide a platform for
measuring flow rate in about real time without contacting the
material being pumped. Pressure and optional temperature sensors
disposed in a pressurized chamber allow for fluid delivery
calculations after being calibrated or by knowing the initial
volume of the fluid to be delivered.
Inventors: |
DiPerna; Paul Mario; (San
Clemente, CA) |
Correspondence
Address: |
Luce, Forward, Hamilton & Scripps LLP
2050 Main Street, Suite 600
Irvine
CA
92614
US
|
Assignee: |
Phluid,Inc.
|
Family ID: |
40899426 |
Appl. No.: |
12/020498 |
Filed: |
January 25, 2008 |
Current U.S.
Class: |
417/54 ;
417/65 |
Current CPC
Class: |
A61M 2205/3368 20130101;
F04B 43/06 20130101; A61M 5/16809 20130101; A61M 2205/3331
20130101; F04B 43/10 20130101; A61M 5/16886 20130101; A61M 5/1486
20130101 |
Class at
Publication: |
417/54 ;
417/65 |
International
Class: |
F04F 1/00 20060101
F04F001/00 |
Claims
1. A device comprising: a pressurizable first chamber; a second
chamber for holding a fluid; at least one flow lumen in fluid
communication with the second chamber; at least one pressure sensor
disposed in the first chamber; and a flow controller disposed along
the flow lumen; a microprocessor for computing flow rate from data
provided by the pressure sensor; wherein a pressurized substance in
the first chamber effects a change of volume of the second chamber;
and wherein the microprocessor controls the flow controller.
2. The device of claim 1, further comprising a fill port for
filling the second chamber with the fluid.
3. The device of claim 1, further comprising at least one
temperature sensor disposed in the first chamber.
4. The device of claim 1, wherein the flow controller is a
clamp.
5. The device of claim 1, wherein the flow controller is a flow
restrictor.
6. The device of claim 1, wherein the first chamber is pressurized
prior to filling the second chamber with the fluid.
7. The device of claim 1, wherein the first chamber is made from an
expandable material.
8. The device of claim 7, wherein the expansion of the expandable
material is a function of the pressure of the first chamber.
9. A device comprising: a pressurizable first chamber; a second
chamber for holding a fluid; at least one flow lumen in fluid
communication with the second chamber; at least one pressure sensor
disposed in the first chamber; a flow controller disposed along the
flow lumen; and a microprocessor to compute at least flow rate of
fluid transferred through the at least one flow lumen from the
second chamber; wherein a pressurized substance in the first
chamber effects a change of volume of the second chamber whereby
the fluid flows from the second chamber through the flow lumen; and
wherein the microprocessor controls the flow controller.
10. The device of claim 9, further comprising a fill port for
filling the second chamber with the fluid.
11. The device of claim 9, further comprising at least one
temperature sensor disposed in the first chamber.
12. The device of claim 9, wherein the flow controller is a
clamp.
13. The device of claim 9, wherein the flow controller is a flow
restrictor.
14. The device of claim 9, wherein the first chamber is pressurized
prior to filling the second chamber with the fluid.
15. The device of claim 9, further comprising at least one
temperature sensor; wherein the microprocessor gathers data from
the temperature sensor to compute the at least a flow rate of fluid
transferred through the flow lumen from the second chamber.
16. A method comprising: providing a pump having: (a) a
pressurizable first chamber; (b) a second chamber for holding a
fluid; (c) at least one pressure sensor disposed in the first
chamber; (d) a flow lumen in fluid communication with the second
chamber; and (e) a flow controller; wherein a pressurized substance
in the first chamber is able to cause the fluid to flow from the
second chamber and through the flow restrictor thereby changing the
volume of the second chamber.
17. The method of claim 17, further comprising providing at least
one temperature sensor disposed in the first chamber.
18. The method of claim 17, wherein the flow controller is a
clamp.
19. The method of claim 17, wherein the flow controller is a flow
restrictor.
20. The method of claim 17, further comprising a microprocessor for
computing flow rate from data provided by the pressure sensor;
wherein the microprocessor controls the flow controller.
Description
BACKGROUND
[0001] The present disclosure relates to the field of pumps,
especially those used to accurately dispense medication.
SUMMARY
[0002] Two chamber pumps and related methods provide a platform for
measuring flow rate in about real time without contacting the
material being pumped. Pressure and optional temperature sensors
disposed in a pressurized chamber allow for fluid delivery
calculations after being calibrated or by knowing the initial
volume of the fluid to be delivered.
[0003] According to a feature of the present disclosure, a device
is disclosed comprising a pressurizable first chamber, a second
chamber for holding a fluid, a flow lumen disposed exterior to the
first chamber and in fluid communication with the second chamber,
at least one pressure sensor disposed in the first chamber, and a
flow controller disposed along the flow lumen. A pressurized
substance in the first chamber is able to cause a: change of volume
of the second chamber.
[0004] According to a feature of the present disclosure, a device
is disclosed comprising a pressurizable first chamber, a second
chamber for holding a fluid, a flow lumen disposed at least
partially exterior to the first chamber and in fluid communication
with the second chamber, at least one pressure sensor disposed in
the first chamber, a flow controller disposed along the flow lumen,
and a microprocessor to compute at least flow rate of fluid
transferred through the flow lumen from the second chamber. A
pressurized substance in the first chamber is able to cause a
change of volume of the second chamber by causing fluid to flow
from the second chamber through the flow lumen and the
microprocessor controls the flow controller.
[0005] According to a feature of the present disclosure, a method
is disclosed comprising providing a pump having: (a) a
pressurizable first chamber, (b) a second chamber for holding a
fluid, (c) at least one pressure sensor disposed in the first
chamber, (d) a flow lumen in fluid communication with the second
chamber, and (e) a flow controller. A pressurized substance in the
first chamber is able to cause a change of volume of the second
chamber.
DRAWINGS
[0006] The above-mentioned features and objects of the present
disclosure will become more apparent with reference to the
following description taken in conjunction with the accompanying
drawings wherein like reference numerals denote like elements and
in which:
[0007] FIG. 1 is a cross sectional view of an embodiment of the
pumps of the present disclosure having rigid outer casings;
[0008] FIG. 2 is a cross sectional view of an embodiment of the
pumps of the present disclosure, where the outer casing of the pump
is a collapsible bag; and
[0009] FIG. 3 is a cross sectional view of an embodiment of the
pumps of the present disclosure.
DETAILED DESCRIPTION
[0010] In the following detailed description of embodiments of the
invention, reference is made to the accompanying drawings in which
like references indicate similar elements, and in which is shown by
way of illustration specific embodiments in which the invention may
be practiced. These embodiments are described in sufficient detail
to enable those skilled in the art to practice the invention, and
it is to be understood that, other embodiments may be utilized and
that logical, mechanical, biological, electrical, functional, and
other changes may be made without departing from the scope of the
present invention. The following detailed description is,
therefore, not to be taken in a limiting sense, and the scope of
the present invention is defined only by the appended claims. As
used in the present disclosure, the term "or" shall be understood
to be defined as a logical disjunction and shall not indicate an
exclusive disjunction unless expressly indicated as such or notated
as "xor."
[0011] According to the present disclosure, the term "real time"
shall be defined as the instantaneous state or lagging the
instantaneous state by the time taken to compute a measurement
describing the instantaneous state, provided the measurement
computed reasonably approximates the instantaneous state at the
beginning of the measurement process and the instantaneous state at
the end of the measurement process.
[0012] The present disclosure discloses a pump that is able to
measure flow rates or adjust flow rates in about real time. The
pumps of the present disclosure comprise two chambers with at least
a pressure sensor disposed therein to measure pressures in a
pressured chamber that drives flow of a fluid from a liquid
chamber. Flow controllers are disposed as part of the pump to
either prevent flow or regulate and ensure consistent flow rate.
The operation of the pumps of the present disclosure maintain
sterile conditions for the fluid flow from the pumps, while
allowing for precise measurements for flow volumes without
compromising sterility.
[0013] According to embodiments and as illustrated in FIG. 1, pump
100 comprises first chamber 110 and second chamber 120. First
chamber is a chamber that is pressurized such that the pressure in
first chamber exceeds the pressure of second chamber. Consequently,
when pump 100 is in an open state, flow of fluid contained in
second chamber 120 is effected.
[0014] Flow of fluid from second chamber is through flow lumen 130.
Flow lumen may be surgical or medical tubing, pipes, and other
similar devices designed for the flow of fluids from a source to a
destination without appreciable loss of fluid.
[0015] According to embodiments, flow controller 140 may be
disposed along flow lumen 130 to control flow. Control of flow,
according to embodiments, may be an on/off type device, such as a
clamp, whereby when flow controller is open flow is effected and
when flow controller 140 is closed, flow is prevented. Flow
controller 140 may also comprise, according to embodiments, a flow
restrictor to ensure constant or predictable flow. According to
embodiments, flow controller 140 may comprise a plurality of flow
restrictors, clamps, etc.
[0016] Fill device 150 is disposed along flow lumen 130 and
facilitates the filling of second chamber 120 with fluid. Fill
device 150 may comprise a one-way valve, according to embodiments,
whereby fluid is flowed through valve and into second chamber 120.
Fill device 150 is a luer actuated port, according to embodiments.
According to optional embodiments, fill valve comprises a device
for putting a prefilled second chamber 120, such as a typical
intravenous bag, into first chamber 110 after which first chamber
110 is pressurized.
[0017] According to embodiments, and as shown in FIG. 1, first
chamber 110 is a chamber that is able to be pressurized. According
to embodiments, first chamber 110 may be made from any suitable
rigid material, for example polycarbonate, ABS, or polyethylene.
According to different embodiments, first chamber 110 may be made
from flexible materials, for example PVC, polyethylene, silicon,
polyurethane, or various rubbers. According to embodiments, first
chamber 110 is sealed to prevent leakage of gas contained therein.
According to embodiments, first chamber 110 may have a valve for
repressurization or adjustment of pressure, as desired. According
to embodiment and as illustrated in FIG. 2, first chamber 110
comprises a bag-like or collapsible device.
[0018] Pressure sensor 115 is disposed in first chamber 100 to
measure pressure at predetermined intervals, as well as initial
pressure readings to be used to determine flow rate. Optionally, a
temperature sensor may also be disposed in first chamber 100 to
improve accuracy of flow measurement. Multiple pressure and
temperature sensors may be used to more accurately determine
pressure and temperature in first chamber 110.
[0019] Second chamber 120, according to embodiments, comprises a
collapsible chamber that holds a fluid without appreciable leakage.
When flow controller is in a state whereby flow is effected, flow
from second chamber is effected by the pressure differential
between first chamber 110 and second chamber 120. Second chamber
may be made from PVC, polyisoprene, silicon, polyurethane, or other
flexible materials.
[0020] According to embodiments and as shown in FIG. 3, second
chamber 120 may be defined by a collapsible or movable diaphragm
225. Rather than collapsing second chamber 120, the movable or
collapsible diaphragm 125 is moved whereby flow is effected.
[0021] To dispense fluid from pump 100, a calibration step is
necessary. The calibration step determines the initial volume of
second chamber 120 (V.sub.2i), which is necessary to determine flow
rate, as described below using the ideal gas law. According to
embodiments, the most simple method for the determination of
V.sub.2i is to know the volume of fluid put into second chamber
120. This is accomplished by injecting a known amount of fluid into
second chamber 120 via fill device 150 or using a disposable second
chamber 120 (i.e., an IV bag) holding a known volume.
[0022] According to embodiments, calibration may also be
accomplished by calculating, using the ideal gas law, the volume of
second chamber 120 from a known starting volume in an empty state.
If second chamber 120 occupies a known empty volume, for example
using the pump of FIG. 3, wherein the diaphragm rests at a set
position when second chamber 120 is empty, for example 0 ml or 10
ml, then prior to filling of second chamber 120 with a fluid, the
pressure and temperature of first chamber are measured. The initial
volume of second chamber 120 is then calculated after fluid is put
into second chamber 120 using an equation to measure flow rate,
which is derived in detail below:
V 2 empty = P 1 i T 1 f ( c - V 2 filled ) P 1 f T 1 i ( 1 )
##EQU00001##
For the purposes of the present application, second chamber 120 has
three discrete states: empty, filled, and flowing. The empty state
defines second chamber when the volume is 0 or a known empty
volume. The filled state defines the second chamber when it is
filled with fluid. The flowing state defines a plurality of volumes
where
V.sub.2filled>V.sub.2flowing>V.sub.2empty (2)
Typically, V.sub.2flowing is representative of the state wherein
fluid is being delivered from pump 100 to a patient, for example.
However, V.sub.2flowing may also be used for calculations during
the filling of second chamber 120 with fluid.
[0023] According to embodiments, flow is effected because the
pressure of first chamber 110 exceeds the fluid pressure in second
chamber 120. Accordingly, flow rate may be calculated with high
precision and in about real time. Prior to determination of flow
rate, the filled state of pump 100 must be measured.
[0024] Calculation of flow rate is based on the ideal gas law, that
is:
PV=nRT. (3)
[0025] Because the total volume of pump 100 is known, that is the
volume of first chamber 110 (V.sub.1) plus the volume of second
chamber 120 (V.sub.2) is a constant, as shown:
V.sub.1+V.sub.2=c. (4)
Thus, as fluid flows from V.sub.2 to a delivery target, such as a
patient, the volume of V.sub.1 increases proportionally.
Consequently, if V.sub.1 is determined in a filled state and
V.sub.1 is determined in a flowing state at a time interval after
fluid begins to flow from second chamber 120, the change in volume
of V.sub.1 over the time interval t is the flow rate over that time
interval.
flowrate = .DELTA. V 2 .DELTA. t = .DELTA. V 1 .DELTA. t ( 5 )
##EQU00002##
where .DELTA.t is the time interval over which .DELTA.V.sub.1 and
.DELTA.V.sub.2 are measured.
[0026] However, the volume of second chamber (V.sub.2) is not
measured directly. Rather, changes in V.sub.2 are measured
indirectly from the changing volume of V.sub.1. Measurements of the
volume of V.sub.1 are accomplished with pressure sensor and
optional temperature sensor.
[0027] Turning again to the ideal gas law, because first chamber
110 is sealed, the number of molecules (n) of gas in first chamber
110 remains constant. Additionally, R is constant. Therefore,
nR=k (6)
where k is a constant. Thus,
PV = kT ( 7 ) PV T = k . ( 8 ) ##EQU00003##
[0028] Because first chamber 110 is sealed, k remains constant
throughout the flow of fluid from second chamber 120. Additionally,
pressure sensor and optional temperature sensor disposed in first
chamber 110 allows for measurement of P.sub.1filled,
P.sub.1flowing, T.sub.1filled, and T.sub.1flowing. Finally, the
filled volume (V.sub.2filled) of second chamber 120 is known, which
allows calculation of V.sub.1filled, and therefore calculation of
V.sub.1flowing. The following equation for first chamber 110
results:
P 1 filled V 1 filled T 1 filled = P 1 flowing V 1 flowing T 1
flowing . ( 9 a ) ##EQU00004##
[0029] Artisans will understand the filled state comprises the end
state at each discrete time interval in which flow rate is
measured. Indeed, according to embodiments, the filled state of the
prior time interval may comprise the filled of the succeeding time
interval, and so forth as shown as the alternative to equation
(9a).
P 1 flowing .tau. = x V 1 flowing .tau. = x T 1 flowing .tau. = x =
P 1 flowing .tau. = x + y V 1 flowing .tau. = x + y T 1 flowing
.tau. = x + y . ( 9 b ) ##EQU00005##
where .tau. is a time interval, when x=0, the flowing state is
equal to the filled state, and y.gtoreq.1 time interval. Artisans
will readily appreciate that .tau. or .DELTA.t may represent the
aggregate time from the start of flow of fluid from second chamber
120 to the time being measured or may be indicative of any
arbitrary time interval after the start of flow of fluid from
second chamber 120 to the time being measured.
[0030] To more clearly illustrate the principle of determining
.DELTA.V.sub.1, temperature will be assumed to be constant for the
purposes of the next set of equations. Thus,
P.sub.1filledV.sub.1filled=P.sub.1flowingV.sub.1flowing. (10)
Therefore, solving for V.sub.flowing of first chamber 110
yields
V 1 flowing = P 1 filled V 1 filled P 1 flowing . ( 11 )
##EQU00006##
However, V.sub.1filled is unknown and must be calculated from the
total volume of pump c and from knowing the filled volume
(V.sub.2filled) of fluid put into second chamber 120:
V.sub.1filled=c-V.sub.2filled (12)
Thus, the total amount of volume flowed may be calculated using the
equation, based on the proportionality of flow between first
chamber 110 and second chamber 120:
flowrate = V 2 flowing - V 2 filled .DELTA. t = V 1 flowing - V 1
filled .DELTA. t ( 13 ) ##EQU00007##
Thus, to determine V.sub.1flowing, we can use the relationship
expressed in equation (ii). As V.sub.1filled is unknown,
substituting known values of c and V.sub.2filled, the following
equation results:
V 1 flowing = P 1 filled ( c - V 2 filled ) P 1 flowing . ( 14 )
##EQU00008##
Using equation (13) and based on the fact that
V.sub.2flowing=|-(V.sub.1flowing)|, flow rate may be calculated
as
flowrate = P 1 filled ( c - V 2 filled ) P 1 flowing - V 1 filled
.DELTA. t . ( 15 ) ##EQU00009##
[0031] Adding temperature back to the equation allows for a more
precise measurement of flow rate and is easily accomplished:
flowrate = P 1 filled ( c - V 2 filled ) P 1 flowing - V 1 filled
.DELTA. t ( T 1 flowing T 1 filled ) . ( 16 ) ##EQU00010##
[0032] According to embodiments, measurements of flow rate are
taken at discrete time intervals. These time intervals may range
from many measurements per second to measurements taken over the
course of minutes, hours, or days, depending on the specific
application. Accordingly, measuring flow rate provides about
real-time feedback, which may be used to adjust flow rate. By
coupling the measurement of flow rate to flow controllers, flow may
be closely regulated. For example, if flow controller 140 comprises
a clamp, then feedback system may open the clamp when additional
flow of fluid is needed and close the clamp when too much flow has
occurred. Thus, the combination of a flow controller and the about
real-time flow measurement provides a platform to deliver
measurably accurate volumes of a fluid.
[0033] According to embodiments, first chamber 110 may be made from
expandable materials. In such embodiments, first chamber 110 may be
a disposable bag or similar flexible-type container such as an
IV-type bag, that tend to expand or contract depending on the
pressure within the first chamber. Thus, the above equations must
account for the effects expansion or contraction due to change of
pressure within first chamber 110. In other words, as pressure
increases, the volume within first chamber 110 will change in a
predictable way and visa versa. For example, by including in the
calculations a factor incorporating the modulus of elasticity of
the material from which first chamber 110 is made into the V.sub.1,
the change in the volume of first chamber 110 is reasonably
predictable.
[0034] Accuracy of the determination of the change in V.sub.1
attributable to the elasticity of the material from which first
chamber is made is improved by calibrating the system at a known
initial pressure of first chamber 110 and volume of second chamber
120. Thus, first chamber 110 is designed and made to have a known
volume in this initial state. As pressure increases, the calculated
additional volume due to expansion of first chamber 110 may be
added to the initial volume to derive an accurate value of
V.sub.1.
[0035] Referring again to the calibration step, as the pressure of
second chamber 120 increases as it is charged with the fluid, the
volume of first chamber 110 is decreased and the pressure within
first chamber 110 increases. At the same time, because first
chamber 110 is made from non-rigid materials there will be
predictable expansion of the dimensions of first chamber 110, with
increased resulting volume. Thus, to determine the actual volume of
first chamber 110 after the initial state, the pressure of first
chamber is measured and volume is calculated as described
previously, taking into account the incremental volume increase or
decrease of first chamber 110 observed due to elasticity of
material from which first chamber 110 is made.
[0036] According to alternative-type embodiments, a method for
accounting for the change in V.sub.1 due to expansion or
contraction of first chamber 110 is to lookup the approximate
change in volume of first chamber 110 as pressure within first
chamber 110 increases or decreases in a lookup table. The lookup
table, according to embodiments, is based upon averaged value for a
plurality of the same first chamber 110 having the same dimensional
parameters and will provide a reasonably approximate factor to add
or subtract to V.sub.1 at a plurality of given measured
pressures.
[0037] These principles are illustrated in the following equations.
Let V.sub.1.sup.E be the supplemental volume of first chamber as
first chamber 110 expands or contracts. In systems where first
chamber 110 is made from rigid materials, the volume of first
chamber 110 plus the volume of second chamber 120 is constant, as
expressed in equation (4).
V.sub.1+V.sub.2=c (4)
In system where first chamber 110 is made from expandable
materials, however, a factor must be added to c denoting the added
or lost volume occurring due to expansion or contraction of the
first chamber 110.
V.sub.1+V.sub.2=c+V.sub.1.sup.E (17)
Thus, the volume of V.sub.1 may be calculated as:
V.sub.1=c+V.sub.1.sup.E-V.sub.2. (18)
[0038] Thus, in systems where first chamber 110 is made from
expandable materials, equation (16) is modified to account for the
expanded first chamber 110:
flowrate = P 1 filled ( c + V 1 E - V 2 filled ) P 1 flowing - V 1
filled .DELTA. t ( T 1 flowing T 1 filled ) . ( 19 )
##EQU00011##
[0039] Artisans will readily recognize that V.sub.1.sup.E may be
calculated if the modulus of elasticity is known or may be simply
recorded as a set of values within a table for quick lookup,
especially in situations where a microprocessor is not designed to
perform series of complex calculations or where power consumption
is an issue.
[0040] While the apparatus and method have been described in terms
of what are presently considered to be the most practical and
preferred embodiments, it is to be understood that the disclosure
need not be limited to the disclosed embodiments. It is intended to
cover various modifications and similar arrangements included
within the spirit and scope of the claims, the scope of which
should be accorded the broadest interpretation so as to encompass
all such modifications and similar structures. The present
disclosure includes any and all embodiments of the following
claims.
* * * * *