U.S. patent number 3,709,222 [Application Number 05/101,636] was granted by the patent office on 1973-01-09 for method and apparatus for automatic peritoneal dialysis.
This patent grant is currently assigned to Sarns, Inc.. Invention is credited to James H. DeVries.
United States Patent |
3,709,222 |
DeVries |
January 9, 1973 |
METHOD AND APPARATUS FOR AUTOMATIC PERITONEAL DIALYSIS
Abstract
A method and apparatus for automatic peritoneal dialysis which
includes a series of steps for the exchange of dialysate which
proportions the in-flow to the out-flow and provides for the
elimination of any distressing in-flow or out-flow pressures on the
patient and any abnormal build-up of fluid quantity in the patient.
The apparatus includes a portable bed-side unit which carries the
necessary pumps and valves for the automatic cycle and includes a
disposable plastic sheet unit supported on the apparatus which is
positioned such that pumps and valves in the apparatus can operate
on this unit when in place.
Inventors: |
DeVries; James H. (Ann Arbor,
MI) |
Assignee: |
Sarns, Inc. (Ann Arbor,
MI)
|
Family
ID: |
22285671 |
Appl.
No.: |
05/101,636 |
Filed: |
December 28, 1970 |
Current U.S.
Class: |
604/28; 604/29;
417/395 |
Current CPC
Class: |
A61M
1/28 (20130101); A61M 1/1639 (20140204); A61M
1/282 (20140204); A61M 1/0023 (20130101); A61M
2205/12 (20130101) |
Current International
Class: |
A61M
1/28 (20060101); A61M 1/16 (20060101); A61M
1/00 (20060101); A61m 005/00 () |
Field of
Search: |
;128/213,214R,214B,214F,214.2,230 ;137/564,5,565,567
;417/349,395 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truluck; Dalton L.
Claims
What is claimed as new is as follows:
1. A method of automatic cycling of peritoneal dialysis which
comprises:
a. introducing a metered quantity of dialysate into a patient,
b. providing a metered quantity of fresh dialysate in a first
expansible, contractible, volumetric container,
c. providing a second expansible, contractible, volumetric
container adjacent the first container,
d. confining the first and second containers within a
non-expansible volumetric housing,
e. transferring a quantity of dialysate from the patient to the
second container to cause ensmalling of said first container,
and
f. introducing fresh dialysate thus forced from said first
container into the patient.
2. A method as defined in claim 1 which includes interposing a
third expansible-contractible container between the first container
and the patient, and positioning the third container relative to
the patient to cause gravity flow of dialysate from the third
container to the patient.
3. A method as defined in claim 1 which includes interposing a
return chamber between the patient and the second chamber, moving
dialysate from the patient to the return chamber, and subsequently
moving dialysate from the return chamber to the second chamber.
4. A method as defined in claim 2 which includes interposing a
return chamber between the patient and the second chamber, moving
dialysate from the patient to the return chamber, and subsequently
moving dialysate from the return chamber to the second chamber.
5. A method as defined in claim 1 which includes providing a waste
receptacle, and intermittently discharging returned dialysate to
said waste chamber from said second chamber subsequent to
introduction of the said dialysate into the second chamber.
6. An apparatus for automatic cycling of peritoneal dialysis which
comprises:
a. a support to be positioned at the bedside of a patient,
b. means on said support for holding a supply of fresh
dialysate,
c. a first expansible, contractible container on said support for
receiving fresh dialysate from said supply,
d. a second expansible, contractible container on said support
directly adjacent said first container,
e. a fixed volumetric chamber on said support confining the
expansion of said first and second containers,
f. first means to flow dialysate to and from a patient, and
g. second means selectively operable to connect said first means to
said second container to permit flow from a patient to said second
container, and to permit flow from said first container to a
patient.
7. An apparatus as defined in claim 6 in which:
a. said second means includes a pressure relief chamber
positionable above the patient having an inlet connected to said
first chamber and an outlet connectable to a patient.
8. An apparatus as defined in claim 6 in which:
a. said second means includes a return chamber to receive return
flow to dialysate from said first means, and
b. third means to move return dialysate from said return chamber to
said second chamber to force fresh dialysate from said first
chamber to said first means.
9. An apparatus as defined in claim 8 in which said third means
includes:
a. a pump connected in a line leading from said return chamber,
b. a float valve in said line at the bottom of said return chamber
to momentarily close said line when the return chamber is empty,
and
c. a vacuum responsive envelope in said line operable to stop said
pump upon emptying of said return chamber.
10. An apparatus as defined in claim 6 in which said second means
includes:
a. a pump connected in a line leading from said first means,
and
b. a pressure relief means in said line to limit negative pressure
in said first means.
11. An apparatus as defined in claim 10 in which said pump is a
peristaltic pump having a positive displacement and a negative
displacement cycle sequentially, and said pressure relief means
comprises a collapsible envelope in said line leading from said
first means.
12. An apparatus as defined in claim 6 in which:
a. a hydrostatically expanded pocket is provided in a line between
the supply of fresh dialysate and said first container to respond
to exhaustion of supply of fresh dialysate to interrupt the
function of said second means.
13. An apparatus as defined in claim 6 in which said support
includes a first panel, and said containers are formed from
overlaid sheets of plastic supported on said panel and heat sealed
in defined areas to form said containers.
14. An apparatus as defined in claim 13 in which a plurality of
collapsible connector lines are heat sealed into said plastic
sheets to provide flow lines for said apparatus.
15. An apparatus as defined in claim 14 in which a plurality of
valve means are supported on said panel operable to squeeze said
connector lines to a close-off position.
16. An apparatus as defined in claim 15 in which a cover panel
overlies said panel, and said valves operate to squeeze said
connector lines against said cover panel to achieve a close-off of
said connector lines.
17. An apparatus as defined in claim 13 in which said fixed
volumetric chamber is formed by a predetermined area of said panel,
and a relatively rigid cover portion overlying said area.
18. An apparatus as defined in claim 7 in which said relief chamber
is mounted on vertically adjustable means on said support to permit
regulation of hydrostatic position relative to a supply of fresh
dialysate.
19. An apparatus as defined in claim 8 in which said support
comprises adjustable panel means for confining the walls of said
return chamber to regulate its expansion as a control means in the
cycling.
20. An apparatus as defined in claim 13 in which:
a. said second means includes a return chamber to receive return
flow of dialysate from said first means,
b. third means to move return dialysate from said return chamber to
said second chamber to force fresh dialysate from said first
chamber to said first means,
c. a cover panel is mounted on said support movable to a fixed
position relative to said first panel, and
d. a movable section is provided on said cover panel overlying said
return chamber shiftable relative to said first panel to regulate
the expansion of said return chamber as a control means in the
cycling.
21. An apparatus as defined in claim 11 in which said pump has a
plurality of rollers spaced circumferentially to provide a positive
displacement cycle during only a portion of the rotative cycle of
said pump.
Description
This invention relates to a Method and Apparatus for Automatic
Peritoneal Dialysis.
It is an object of the present invention to provide a system and
apparatus for use in peritoneal dialysis which requires a minimum
of attention by skilled hospital personnel and which has a number
of safety features relative to the elimination of infection and
discomfort.
It is an object of the invention to provide a system and apparatus
which will maintain fluid balance to monitor the amount of fluid
administered to the patient, thus preventing a build-up of the
fluid quantity over a period of operation.
It is a further object to provide a system which can be
automatically cycled and which will warm the dialysate to maintain
a certain temperature range when additional dialysate is added to
the quantity in use.
It is a further object to provide a system which prevents
continuing operation in the event of a negative pressure build-up
in the outflow and also a system which will control maximum volume
in the cycle and interrupt the cycle if a fluid source is
exhausted.
The invention also contemplates the use of a disposable bag element
in cooperation with a support apparatus which is relatively
inexpensive compared to the overall apparatus and which permits a
fresh series of chambers to be used for each patient.
Another object of the invention is a mounting apparatus for the
various elements of the system which adapts itself to and
cooperates with the disposable elements.
Other objects and features of the invention relating to details of
construction and operation will be apparent in the following
description and claims in which the principles of the invention are
set forth in connection with the best mode presently contemplated
for the invention.
DRAWINGS accompany the disclosure and the various views thereof may
be briefly described as:
FIG. 1, a perspective view of the system showing the apparatus and
the relationship to the patient.
FIG. 2, a sectional view taken on line 2--2 of FIG. 4 of the
support cabinet showing the manner in which the mechanically
operated valves are related to the system.
FIG. 3, a rear elevation of the valve mechanism.
FIG. 4, a view of the support apparatus cabinet with the door in
open position.
FIG. 5, a view of certain disposable portions of the apparatus
separated from the supporting cabinet.
FIGS. 6, 7, 8, and 9, partial sectional views taken on lines 6--6,
7--7, 8--8, and 9--9 of FIG. 5.
FIG. 10, a view of a waste bag element for the system.
FIG. 11, a sectional view on line 11--11 of FIG. 10.
FIG. 12, a view of the opening of the neck portion of the waste bag
in closed position.
FIG. 13, a sectional view on line 13--13 of FIG. 12.
FIG. 14, a sectional view of the apparatus showing the return
chamber of the system and associated control elements.
FIG. 15, a sectional view of the proportioning chamber of the
system in relation to the controlling portions of the support
apparatus.
FIG. 16, a sectional view taken on line 16--16 of FIG. 4 of a
portion of the apparatus showing a sensor control switch.
FIG. 17, a sectional view on line 17--17 of FIG. 4 of a second
sensing switch and response portion of the apparatus.
FIG. 18, an elevation of a peristaltic pump utilized in the
system.
FIGS. 19, 20, and 21, sectional views taken on lines 19--19,
20--20, and 21--21 of FIG. 18.
FIG. 22, a diagrammatic view illustrating the system disposed for
flow of fluid to the patient.
FIG. 23, another diagrammatic view showing the condition of fluid
return from the patient.
FIG. 24, a view of a float valve with an orifice leak by-pass.
FIG. 25, an electrical diagram showing various control elements of
the system.
REFERRING TO THE DRAWINGS
In FIG. 1, the apparatus is shown adjacent a hospital bed 30 on
which is resting a patient 32 who has received the insertion of an
abdominal catheter 34 leading from the apparatus. The apparatus
consists of a main cabinet 36 having a door 38 which is hinged to
be moved to an open position.
Cross-wise of the cabinet 36 on one end is an open topped case 40.
A frame formed by cross members 41 and axles 42 and 44 is supported
on wheels or castors 46 and 48. A control panel 50 is mounted on
the top of the cabinet. On the side of the cabinet 36 mounted in
suitable brackets 51 is a stanchion tube 52 which extends upwardly
to hold two horizontal cross bars 54 and 56 which can support a
supply of sterile dialysate in vessels 58 and 60. Mounted on the
stanchion tube 52 is a slide bracket 61 which supports a vertical
rod 62 shiftable from the solid line position shown in FIG. 1 to a
dotted line position also shown wherein a horizontal portion 64 of
the rod can support a plastic relief chamber bag 66 forming part of
the system.
Valves which open and close certain tubes of the system, as will be
later described, are shown in cross-section in FIG. 2. These are
mounted on a panel 70 lying behind the door 38 of the cabinet on a
bracket 72 (see FIG. 3), this bracket having a horizontal plate 74
which supports a motor 76 which drives a reduction gear 78 leading
to an eccentric driven crank 80. This crank moves a plunger 82
forward and aft, the plunger being sealed by a grommet 84 in the
wall of the plate 70. The plunger has a chamfered nose portion 86
which can drive forward against the door plate 38 to close off a
particular tube in the system. Suitable control elements for the
motor will actuate these valves in response to the general system.
There are four such valve control units mounted on plate 70 and
viewing FIG. 4 these are referenced as V-1, V-2, V-4 and V-5. The
functions of these valves in connection with the system will be
described relative to certain tubes in the system at the
appropriate time.
Other hardware on the cabinet includes, as illustrated in FIG. 4,
two rotating peristaltic pumps indicated generally at 90 and 92.
Except as will be later described, these are of standard
construction and are driven by suitable motors mounted in the
cabinet 36 behind the panel 70. Additional structure is shown in
the sectional view of FIG. 14 where it will be seen that at the
bottom portion of the plate 70 is a recess 94 which is closed by a
swinging panel 96 hinged at 98.
Behind this panel is a micro-switch actuator roller 100 on arm 102
connected with micro-switch 104. The door 38 has an opening 106
(see FIGS. 4 and 14) which also is closed by a swinging panel 108
hinged at 110. The position of the plate 108 can be adjustably
regulated by an adjustment screw 112 on bracket 114. The purpose of
this compartment between plates 96 and 108 will be described
later.
Another compartment that is formed in the system by a portion of
plate 70 and the cover 38 is shown in cross-section in FIG. 15.
Plate 70 is again apertured and this aperture is provided with a
shaped panel member 116 which is dished as shown in the drawing. On
the back of this dished member is a small electric heater 118 which
will be used to maintain a temperature level of liquid in the
system. The door panel 38 is also provided with a recess which is
filled by a dished member 120 essentially symmetrical with the
member 116 to provide an elongate substantially rectangular,
rigid-walled compartment. At the lower central portion of the plate
70, as viewed in FIG. 4, is an opening 130 shown in FIG. 17 below
which is a bracket having a horizontal plate 132 on the left side
and a horizontal plate 134 at a slightly higher level on the right
side as viewed in FIG. 17. Positioned at the opening 130 on bracket
plate 132 is a micro-switch arm 136 which controls a micro-switch
138. The purpose of this micro-switch in conjunction with the fluid
system will be described later.
At the upper left-hand corner of the plate 70 is an opening 140
(FIG. 16) below which is mounted a bracket plate 142 supporting a
micro-switch 144 operated by a switch arm 146. This switch arm is
influenced by the pocket 224 (FIGS. 5 and 7) to reflect absence of
hydraulic head in the supply line from containers 58, 60. It will
be noted also that the door has an opening 150 which overlies the
pumps 90 and 92 so that the operation of these pumps may be
observed from outside the cabinet when the door is closed. The door
has a latch handle 152 which cooperates with a latch 154 on a wall
of the cabinet 36. The plate 70 also carries a plurality of
projecting pins 156 positioned at the top and bottom and at other
points on the left-hand side of the plate for the supporting of a
plastic container and conduit sheet 160. This sheet is shown in
FIG. 4 illustrated in greater detail in FIG. 5 where it is shown
apart from the supporting panel. A detailed description
follows.
The pumps 90 and 92 are relatively standard peristaltic pumps,
FIGS. 18-21, having a rotor 170 mounted on a drive shaft 172 and
carrying guide wheels 174, which rotate on pins 175 within a
housing wall 176, and pressure rollers 178 on pins 179 which exert
rolling pressure on a tube lying against the inside of the wall.
The pump 92 differs from the normal pump in that one pressure
roller at the roller mount 180 is omitted to permit a periodic
pressure equalization as will be later described.
Referring now to FIG. 5 and related sectional views in FIGS. 6 to
9, there is shown the plastic container and conduit sheet 160. This
container sheet is intended to be disposable to avoid the
sterilization problems incident to the use of reusable containers.
The sheet is made from a plastic which is preferably transparent,
or at least translucent, and heat sealable. Chambers are formed, in
the double or folded-over sheet, by heat sealing the peripheries,
and plastic tubes are heat sealed into these chambers, FIG. 6, to
provide the necessary ingress and egress.
Specifically with reference to FIG. 5, a return chamber 200 is
formed in the lower area by a heat sealed periphery 202 with an
outlet 202 with an outlet tube 203 sealed at 204, this tube having
an arched portion with a top air vent 205. A bottom tube 206 leads
to a float valve entry unit 207 within the chamber and to a
collapsible sensor pocket 208 (FIG. 17 is cross-section) and thence
through a pump tube 209, 209a, 209b to a sealed entrance to one
side of a proportioning chamber 210 again formed by a heat sealed
periphery. The float valve 207 is designed to close outlet tube 206
when chamber 200 is depleted, FIG. 24. A small orifice 207a permits
a bleeding action to relieve negative pressure.
A lower outlet tube 212 leads out of one side of the proportioning
chamber 210 in the sheet to a connector 213 which will join to a
waste chamber connector 214 on a plastic waste chamber bag 216
lying in compartment 40 (FIGS. 1 and 10). The vented tube 203 from
the return chamber also connects at 218 to the waste chamber bag
216. At the top of the proportioning chamber 210 one side of the
chamber is connected through a sealed tube 220 to a point near the
top of the elevatable pressure relief chamber bag 66 (FIG. 1). A
second tube 222 at the top of the proportioning chamber 210 leads
through a small pocket chamber 224 (FIG. 7 in cross-section) to a
tube 226 which has a bifurcate connector 228 which joins tubes
leading to supply containers 58 and 60 (FIG. 1).
The pressure relief chamber 66 also has a connector tube 230 into
the bottom which leads to a bifurcate connector 232, the single
outlet of which leads to patient tube 234 and body chamber catheter
34. The other branch of the connector 232 leads through a pressure
relief pocket 236 (FIG. 9 in section) and then to a tube 238
entering the plastic container sheet 160 to a bacterial trap 240
recessed into the sheet 160 and having a connector tube 242 leading
to a pump tube 242a and a connection to a re-entry tube 242b in
sheet 160 sealed into the top of return chamber 200.
The proportioning chamber 210 actually consists of two side-by-side
chambers which are created by sandwiching a diaphragm or separation
wall 250 between the walls 252 and 254 formed from the double
sheets. (See FIGS. 8 and 15). This forms two chambers 260 and 270,
the chamber 260 on the right, as viewed in FIG. 15, serves to
receive return dialysate fluid through tube 209(b) and, under some
circumstances, to discharge it to tube 212 and the waste chamber.
The chamber 270 on the left, a s viewed in FIG. 15, serves to
receive fresh dialysate fluid from tube 222 through pocket 224 and
can introduce this fresh fluid into relief chamber 66 through tube
220. These two chambers 260 and 270 have a volumetric effect on
each other as will be described. It will be noted that these two
chambers 260 and 270 are encased between the rigid dished plates
116 and 120 of the cabinet wall 70 and cover 38 as shown in the
sectional view of FIG. 15. Thus, the expansion of one chamber will
cause ensmalling of the other and vice versa. There can then be a
volumetric proportioning or balancing occur by reason of this
arrangement.
The return chamber 200 lies in the compartment formed by the plate
96 and the plate 108 shown in FIG. 14 so that the volume of the
chamber 200 can serve as a control by reason of pressure against
the movable plate 96 which will influence the micro-switch arm 102.
The pocket 208 at the lower right-hand portion of the chamber
sheet, supported on bracket 134, as shown in FIG. 17, has a
possible influence on the switch arm 136, and the pocket 224 shown
in section in FIG. 16 is a collapsible pocket which will reflect a
reduction in pressure in the return flow line and thus influence a
micro-switch arm 146.
The previously described close-off valves V-1, V-2, V-4 and V-5,
which may be referred to as "clamp" valves, are shown in phantom on
FIG. 5 to indicate the particular tubes that they are controlling.
V-1, for example, controls tube 222; V-2 control tube 220; V-4
controls tube 242; and V-5 controls tube 212.
Referring to FIGS. 10 to 13 the waste bag 216 is formed of a double
sheet of plastic with holes 280 and 282 for suspending the bag in
the compartment 40, this bag being sealed around its edges as
illustrated in FIG. 11. The two top connector tubes are also sealed
into the bag at 284. The bag has an outlet neck portion 286 which
has a flap assembly 288 containing a malleable metallic stiffener
290. When the bag is to be used, this closure neck can be sealed by
folding over the tab portion 290 and bending the ends to a locking
position as shown in FIGS. 12 and 13.
Function and Operation
The function of the apparatus above described is to administer
dialysate to a patient over long periods of time in a manner to
reduce the need for constant supervision by a nurse or technical
attendant. The machine must maintain fluid balance, i.e., monitor
the amount of fluid administered to the patient to avoid the danger
and discomfort of fluid build-up in the peritoneal chamber of the
patient; it must also automatically cycle the flow of dialysate and
warm the dialysate which will enter the peritoneal chamber. In
addition, the machine must be safe and simple to operate and
maintain sterility of the system.
It will be recognized that the machine has, first, an electrical
cycling unit with a suitable "Power On" switch 292 which controls
inflow pump 90 and return pump 92 and the four clamp valves V-1,
V-2, V-4, V-5. Other functional elements in the electrical system
are a starting switch 294, the micro-switches 104 (FIGS. 4, 14),
138 (FIGS. 4, 17) and 144 (FIGS. 4, 16), and timers T1, T2 and T3.
An electronic circuit system system is shown in FIG. 25
illustrating the controlling circuit elements and sequence of
operation.
The second basic element of the machine is the replaceable or
disposable, flexible, plastic sheet and tube fabrication 160 which
can be initially pre-sterilized.
A third basic element of the apparatus is the proportioning
reservoir or chamber (FIGS. 4, 15) which consists essentially of
the side-by-side chambers 260 and 270 formed by the lamination of
the three sheets 250, 252, 254 confined between rigid dished walls
116 and 120. One of the chambers can be filled to the total volume
of the rigid housing. If fluid is then subsequently forced into the
second chamber, it will force an equal volume out of the first
chamber through movement of the intermediate wall 250 which acts as
a diaphragm piston. Fluid balance in the patient is achieved by
filling one chamber 270 with fresh sterile dialysate prior to the
inflow cycle. During inflow, the fluid returned from the previous
cycle is pumped into the second compartment 260, thus forcing an
equal volume of fresh sterile dialysate into the patient. Thus, the
proportioning chamber serves the function of a pump.
In FIGS. 22 and 23, a schematic presentation of the apparatus is
illustrated. With reference to these views and the previously
described detailed views, to start the cycle, the pressure relief
chamber 66 is raised on rod support 64 above the source bottle 58
before the pumps are started. With the clamp valves open, sterile
fluid will flow into proportioning chamber 270 through tube 226
until chamber 270 completely fills the rigid chamber 116, 120. The
pressure relief chamber is then lowered below the fluid sources 58,
60 to allow fluid to flow to it through valve V-2 and line 220 and
then to the line 230 and line 234 which will be connected to the
patient. After this catheter line is filled, it is manually
clamped. The return pump 92 will pump fluid from the connector 232
to the return chamber 200 where fluid will accumulate until switch
arm 102 trips micro-switch 104 to stop the motor of the return pump
92. At this time the fluid supply line 226 is manually clamped. At
the same time the inflow pump is automatically turned on and clamp
valve V-4 is closed electrically. The inflow pump moves the
contents of the return chamber 200 into the waste chamber 216,
thereby priming all the lines. The depletion of the liquid in
chamber 200 causes pump 90 to create a negative pressure in
collapsible pocket 208, thus triggering micro-switch 138 through
arm 136 bearing against the pocket to automatically stop inflow
pump 90. The float valve 207 closes when liquid leaves the bottom
of chamber 200 causing the negative pressure in pocket 208 but an
orifices 207a (FIG. 24) permits enough fluid to leak by to allow
pocket 208 to return to its normal configuration which will reset
switch 138.
At this time the adjustable plate 108 (FIG. 14) can be moved to a
position which allows the return chamber to hold a maximum volume
equal to the desired exchange volume for a particular patient. This
affects the action of plate 96 and micro-switch 104. Now the body
catheter 34 can be connected to the patient. The manual clamp is
now removed from inflow tube 226 and from the catheter tube 234 and
a measured amount of fresh fluid is allowed to run through the
lowered pressure relief chamber into the patient. This relief
chamber is now moved to its upper position above the fluid source
to prevent additional fluid from flowing into the patient.
The machine is now ready for automatic cycling. A suitable start
switch 294 on a control unit connected in the electric control
circuit is manually actuated to initiate the outflow phase. This
opens valve clamps V-1, V-4 and V-5 while V-2 remains closed.
This condition is shown in FIG. 23. The return pump 92 is turned on
and two timers T1 and T2 are energized. Timer T1 controls the
length of the outflow phase. Timer T2 serves as a check on the
outflow from the patient. If the switch 104 sensing hinged plate 96
does not close before timer T2 times out, the first timer T1 is
reset and stops until switch 104 closes. This combination prevents
the machine from automatically advancing if the return from the
patient is less than the desirable rate and indicates a corrective
action by the nurse such as catheter manipulation.
When timer T1 times out, the next phase of operation is initiated.
Valve clamp V-2 is opened and the return pump 92 is stopped and an
optional add cycle is started. The amount of return is observed by
the operator. If it is less than desirable, the pressure relief
chamber 66 is again lowered and the return pump is manually turned
on until the volume in the return chamber is increased to the
desired level. The pressure relief chamber is again raised. Once
the volume has been determined to be adequate, a start switch 294
(FIG. 25) is closed and the inflow cycle begins.
During the inflow cycle, valve clamps V-1, V-4 and V-5 are closed
and V-2 is open. See FIG. 22. Inflow pump 90 is turned on to pump
the fluid from the return chamber 200 into the proportioning
chamber 260 through tubes 209, 209a, 209b, thus forcing fresh
dialysate from charged chamber 270 into the pressure relief chamber
66 from whence it flows into the patient. The pressure relief
chamber is constructed of flexible plastic and has a greater volume
than that of the rigid housing 116-120 of the proportioning
chamber. Also, the inlet 220 to the relief chamber is near the top,
while the outlet to tube 230 is at the bottom. If the line to the
patient is blocked, fluid will accumulate in the pressure relief
chamber exerting a maximum hydrostatic force on the patient
determined by its height above the patient.
When the return chamber empties, the switch 138 closes (by closing
of float valve and collapsing of pocket 208) and the next phase of
the cycle, namely, the equilibration phase, is started. In this
phase, valve clamps V-2 and V-4 are closed and V-1 and V-5 are
open. Both pumps are off. A timer T3 is energized which controls
the length of this phase. Sterile fluid flows from the source 58,
60 into the proportioning chamber 270. This forces the fluid in
chamber 260 into the waste chamber 216 through tube 212 and
connector 213. Also the heater 118 transmits heat to the fresh
dialysate. When timer T3 times out, the unit is automatically
switched back to the outflow cycle which has previously been
described.
There are several control features in the apparatus not touched
upon previously. If, for example, the amount of return fluid
exceeds the intended volume as regulated by panels 96 and 108, any
excess fluid will flow out of the top of the return chamber through
line tube 204 directly into the waste chamber 216. The air vent 205
prevents siphoning once the flow has started.
If switch 144 is triggered by a collapse of flexible pocket 224
(FIG. 16) indicating no hydrostatic head from the supply line 226,
the cycle will be interrupted, and, after replenishment, the
restart switch must be actuated. The cycle can also be altered by
actuating an increase switch 300 (FIG. 25) to replenish fluid when
pump 92 is on. Otherwise, the device will continue to cycle:
inflow, return, equilibration, inflow return and so on.
In FIG. 25, an electronic control system is illustrated for the
purpose of accomplishing the cycling previously described. The
electronic control unit has seven control banks or columns A, B, C,
D, E, F, and G and an input signal to any particular column or bank
cancels the output of any previous column. When a column receives
an input, all actions indicated must take place prior to an output
signal which may lead to another bank.
Each of these banks controls valves V-1, V-2, V-4 and V-5, pump 92
and pump 90. The circuit also shows the location of a start switch
294 and control switch 104, 138 and 144 as well as timers T1, T2
and T3. A power-on switch is shown at 292 and a starting switch 294
is indicated at three points in the circuit. On the electronic
panel, the designation "O" is for "open" along the horizontal lines
leading to each controlled valve or pump and the designation "C"
means "closed."
Switches which are normally open are shown with parallel lines and
switches which are normally closed are shown with parallel lines
crossed by an oblique line.
It will be seen that with the power switch 292 on, bank A will
carry current to the normally open switch 104 and also turn on
return pump 92. When switch 104 is closed by liquid in the return
chamber (FIG. 14), current will then flow to bank B closing valve
V-4, turning off pump 92, and turning on the inflow pump 90. Fluid
will then flow into the waste chamber 216 and ultimately cause the
triggering of micro-switch 138 which will pass signal current from
bank B to bank C. This will leave valve V-4 on and turn off pump
90. At this point, the circuit is ready for cycling and when the
start switch 294 is actuated, the electrical signal will then go to
bank D, closing valve V-2 and turning on the return pump 92. Signal
current out of bank D will ordinarily pass through the normally
closed timer switch T2 and pass to T1; and when timer T1 is phased,
current will then flow through a normally closed add switch 296 and
through normally closed switch 144 to bank E where all valves are
open and the pumps are off. This bank E might function in an "add"
cycle.
Current can also pass then through the start switch 294 to bank F
where valves V-1, V-4 and V-5 are turned off and inflow pump 90 is
turned on. This portion of the cycle will continue until switch 138
is triggered by a depletion of the liquid in the chamber 200 when
current will flow around to bank G, thus opening valve V-1 and
closing V-2, leaving V-4 closed, and opening V-5 with both pumps
being off. This circuit then moves to the timer T3 which is
normally open and when this timer is phased, the circuit will
recycle by starting again at bank D. The timer T3 is controlling
what is called the equilibration phase of the cycle which has been
previously described. The electronic circuit in FIG. 25 also shows
an add switch 296 which can be actuated manually if fluid is to be
added and it also includes an increase switch 300 which can be
actuated with pump 92 on to increase the fluid in the circuit.
As will be seen from the above-detailed description, timer T2 which
is in the "out" circuit from bank D serves as a check on the
outflow from the patient. If the switch 104 does not close before
timer T2 times out, the first timer T1 is reset and stops until
switch 104 closes.
The maximum negative pressure is controlled during the outflow
phase by two devices. Return pump 92 acts as a positive
displacement pump during most of its cycle but one roller at roller
pin 180 (FIG. 18) is removed so that at a certain point in the
rotation, the pump tube 242a is open and unrestricted, thus
relieving the negative pressure on the catheter. Secondly, a
collapsible chamber 236 in tube 238 (FIG. 9) normally returns to
its expanded maximum volume shape if there is no negative pressure
within it. The maximum volume of this chamber 236 is greater than
the stroke volume of the pump and should the inflow tube 234 be
blocked, the pump will collapse chamber 236 during the positive
displacement cycle and prevent transmission of any undue negative
force to the catheter. The maximum negative force created by the
walls of the chamber 236 can readily be calibrated and controlled
by the geometrical configuration and the selected material. During
the balance of the pump cycle, the open tube 242a will permit
retrograde flow and relief of negative pressure and the collapse
chamber 236 can return to its normal expanded configuration.
It will be noted that one function of the pressure relief chamber
is to prevent flow into the patient if clamp valves V-1 and V-2
should fail since the height of the chamber is above the fluid
source 58 and 60. The relation of the tubes 220 and 230 prevent
positive pump pressure reaching the patient tube 234 during a
regular cycle or when liquid is flowing from the supply bottles. If
the patient tube 234 should become blocked, there can be no great
build-up of pressure, positive or negative, which would cause
discomfort of the patient. If switch 138 should fail, the maximum
volume pumped is determined by the maximum volume of the
proportioning chamber which is established at a safe level. Also,
of course, the adjustment of panel 108 determines maximum volume.
The normal volume returned to the patient is equal to the return
volume of the previous cycle.
* * * * *