Abstrict A coronary artery graft flow-meter apparatus for insertion into
a delivery line for solution to be perfused through a graft after
the graft is anastomosed to a coronary artery is disclosed. The
apparatus comprises a flow-meter chamber having an upper end and
a lower end, the upper end having an inflow port and the lower end
having an outflow port. The chamber includes a plastic bag positioned
therein which is adapted to communicate with a volumetric container
containing the solution. The solution flows from the volumetric
container to the plastic bag thereby providing a measurement of
the flow rate of the solution through the graft.
Claims What is claimed is:
1. A coronary artery graft flow-meter comprising:
a flow-meter chamber having an inflow port for receiving a first
liquid and an outflow port for expelling said liquid to said artery
graft;
means for controlling the passage of said first liquid into said
flow-meter chamber;
an inflatable bag located in said flow-meter chamber,
volumetric container means for holding a second liquid;
means for transferring said second liquid from said volumetric
container means to said inflatable bag, wherein said inflatable
bag receives said second liquid when said control means prevents
passage of said first liquid into said flow-meter chamber; and
means for measuring flow of said second liquid from said volumetric
container means to said inflatable bag.
2. The flow-meter of claim 1 further including a pump connected
to said outflow port.
3. The flow-meter of claim 2 wherein said first liquid is cardioplegia
solution.
4. The flow-meter of claim 3 wherein said liquid transfer means
includes a multi-fenestrated tube located in said bag.
5. The flow-meter of claim 4 further comprising positioning means
having a first side and a second side, wherein said volumetric container
means is retained on said first side and said flow-meter chamber
is retained on said second side.
6. The flow-meter of claim 5 wherein said positioning means is
rotatable to a first position, thereby raising said volumetric container
means and lowering said flow-meter chamber to facilitate measurement
of said flow of said second liquid from said volumetric container
means to said bag.
7. A method of measuring liquid flow through a coronary artery
graft using a flow-meter chamber containing an inflatable bag, said
method comprising the following steps:
first, establishing a first liquid flow path from a first liquid
reservoir to said inflatable bag;
second, establishing a second liquid flow path through said flow-meter
chamber to said coronary artery graft;
third, stopping flow of said second liquid through said flow-meter
chamber to thereby start flow of said first liquid from said reservoir
to said inflatable bag; and
fourth, measuring said first liquid's rate of flow from said reservoir
to said inflatable bag.
Description BACKGROUND OF THE INVENTION
The invention of this application relates to a coronary artery
graft flow-meter. More particularly, this invention relates to a
coronary artery graft flow-meter apparatus for insertion into a
delivery line for solution to be perfused through grafts after the
grafts have been anastomosed to coronary arteries.
Indirect flow-meters for coronary artery grafts have been notoriously
unreliable and most open-heart surgery centers no longer use them.
Direct flow-meters have the disadvantage of possible contamination
and/or air embolization. Consequently, there has been a substantial
need for a device which is able to overcome both of these possible
sources of danger and which would provide a disposable, low-volume
closed system that can be inserted into the delivery line for the
cardioplegia solution or cold solution which is perfused through
grafts after they have been anastomosed to the coronary arteries.
Various flow-rate sensing systems and auto-transfusion systems
have been previously suggested. Abrams, U.S. Pat. No. 4613325
describes a flow-rate sensing device for use in regulating the rate
of flow in a system for parenteral administration of liquids to
patients. The liquid emerges from a storage reservoir and is fed
into a housing through an upstream flow passage portion and is then
made to pass through a narrow flow passage wherein the velocity
of the liquid increases while its pressure decreases. The liquid
then emerges into a downstream flow-through passage and flows through
an outlet from the housing. A pressure transducer, consisting of
two chambers separated by a resilient deformable diaphragm, has
its upstream chamber in fluid pressure communication with the upstream
flow path portion and its downstream chamber in fluid and pressure
communication with the flow emerging from the throat passage. Variations
of the flow rate through the throat passage effect changes in the
pressure differential between the transducer chambers and thus cause
variable degrees of displacement of the transducer diaphragm.
Bartlett, U.S. Pat. No. 4547186 describes a system for autotransfusion
which has an aspirating wand or tube coupled to a vacuum source
through a reservoir for receiving aspirated blood. Blood flows from
the reservoir to a receiving bag in a relatively low position below
the elevation of the patient. When there is sufficient blood supply
in the bag, it is elevated from this lower position to a point higher
than the patient. Blood then flows from the elevated bag by gravity
through a conducting tube and a needle into the patient.
Schmid-Schonbein et al., U.S. Pat. No. 4474538 describes a method
of circulating organo-biological fluids wherein a fluid contained
in a reservoir is released to a pressure level lower than its original
fluid pressure level. Thereafter, it is raised periodically to a
pressure level above the original level, then transferred from such
level to a reservoir position at a predetermined, relatively lower
pressure level. It is then drained to an outlet position approximately
at the level of the original pressure level.
Welch et al., U.S. Pat. No. 4014329 describes a method and device
for autotransfusion of blood during surgery. Shed blood is retrieved
from a surgical field via a receiving vessel located within a vacuum
chamber and under less vacuum than the vacuum applied to the chamber.
The vacuum and receiving vessel draw blood from the surgical field
into the receiving vessel where it is first collected and then passed
to a second vessel. The blood is transferred from the second vessel
to the patient during reinfusion.
Rosenberg, U.S. Pat. No. 3896733 describes a continuous-flow
two reservoir fluid or blood-feed system for administration of fluids
to patients. The apparatus is composed of two reservoirs each filled
by way of check valves from a common supply and having common connections
to a vacuum line. Application of vacuum draws the fluid from the
supply line into one of the reservoirs, while fluid is led from
the other reservoir to the patient.
DeVries, U.S. Pat. No. 3709222 describes 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. It includes a disposable sheet unit supported on
the apparatus which is positioned such that pumps and valves in
the apparatus can operate on the unit when it is in place.
Gorsuch, U.S. Pat. No. 3690318 describes an apparatus which
is mounted adjacent to a patient which supports an inspection chamber
at a predetermined elevation with respect to the patient. The chamber
is connected to the patient through an infusion supply tube. Intravenous
infusion fluid is supplied from a container to the inspection chamber
at a predetermined pressure and a selected rate. Fluid level sensors
give warning if the fluid level in the inspection tube rises or
falls a preselected amount.
Robicsek, U.S. Pat. No. 3017885 describes means for measuring
the flow of blood through an artificial heart-lung pumping system.
The means comprise a blood flow meter which is attached directly
to a conduit through which blood flows from the heart-lung pump
to the patient. It includes means for measuring the drop in fluid
pressure as the blood flows through a constriction in the conduit.
The pressure drop therein is said to be proportional to the rate
of flow of the blood.
Buckberg et al., U.S. Defensive Publication No. T994001 describes
a delivery system for injecting a cardioplegic solution made up
mostly of a patient's own blood into his or her heart in order to
arrest it. The delivery system is used in combination with a cardiopulmonary
by-pass apparatus. The delivery system includes a blood bag for
storing a portion of the patient's blood, a Y-shaped tubing having
a first end with a single opening and a second end with a pair of
openings with the single end mechanically coupled to an oxygenator
so that the blood will travel from the oxygenator to the Y-shaped
tubing, and a heat exchanger disposed between the blood bag and
one of the pairs of openings of the second end of the Y-shaped tubing
and connected thereto so that blood may be pumped from the oxygenator
through the heat exchanger into the blood bag by a first small roller
pump.
Heretofore, none of the flow rate systems for coronary artery grafts
provided reliable and safe measurements of the rate of flow through
such grafts. The invention disclosed herein comprises a coronary
artery graft flow-meter apparatus for insertion into a delivery
line for solution to be perfused through a graft after the graft
has been anastomosed to a coronary artery or arteries and which
provides a measurement of the flow rate of the solution through
the graft.
SUMMARY OF THE INVENTION
The present invention contemplates a coronary artery graft flow-meter
apparatus for insertion into a delivery line for solution to be
perfused through grafts after the grafts have been anastomosed to
coronary arteries.
In one aspect of the present invention, the coronary artery graft
flow-meter apparatus of the invention comprises a flow-meter chamber
having an upper end and a lower end. The upper end has an in-flow
port and the lower end has an outflow port therein, which is connected
to a pump. The flow-meter chamber includes a plastic bag positioned
therein which is adapted to communicate with a volumetric container
containing solution, such as cardioplegia solution. The solution
flows from the volumetric container to the plastic bag thereby providing
measurement of the flow rate of the solution through the graft.
In a further aspect of the present invention, the plastic bag of
the coronary artery graft flow-meter apparatus of the invention
is collapsible and contains a multifenestrated tube which is capable
of filling and emptying the bag.
In another aspect of the present invention, the volumetric container
and flow-meter chamber of the graft flow-meter apparatus of the
invention are retained on opposite sides of positioning means which
are rotatable clockwise and counter-clockwise to raise and lower
the volumetric container and flow-meter chamber, respectively.
The present invention provides several benefits and advantages.
One benefit of the present invention is that the graft flow-meter
apparatus of the invention can be inserted into the delivery line
for the cardioplegia solution which is perfused through grafts after
they have been anastomosed to coronary arteries.
Another benefit of the present invention is that the graft flow-meter
apparatus of the invention provides a reliable and safe measurement
of the flow rate of cardioplegia or cold solution through a coronary
artery graft.
One of the advantages of the present invention is that the graft
flow-meter of the present invention is a disposable, low-volume
closed system.
Another advantage of the present invention is that the graft flow-meter
apparatus of the invention is reliable and accurate and minimizes
the possibility of contamination or an air embolism occurring.
Other benefits and advantages of the present invention will become
readily apparent to those skilled in the art from the following
detailed description of the invention, the drawings and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings forming a portion of the disclosure of this invention:
FIG. 1 is a perspective view of the coronary artery graft flow-meter
apparatus of the present invention;
FIG. 2 is a perspective view of the upper end of the flow-meter
chamber of the graft flow-meter apparatus of the present invention;
FIG. 3 is a perspective view of the lower end of the flow-meter
chamber of the graft flow-meter apparatus of the present invention;
FIG. 4 is a perspective view of the positioning means of the graft
flow-meter apparatus of the present invention;
FIG. 5 is a perspective view of the graft flow-meter apparatus
of the present invention illustrating the effect of rotating the
positioning means in a clockwise manner;
FIG. 6 is a perspective view of the graft flow-meter apparatus
of the present invention illustrating the effect of rotating the
positioning means in a counter-clockwise manner; and
FIG. 7 is a perspective view of the positioning means of the graft
flow-meter apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a coronary artery graft flow-meter
apparatus for insertion into a delivery line for solution to be
perfused through a graft after the graft has been anastomosed to
a coronary artery.
With general reference to FIGS. 1-7 a preferred embodiment of
the coronary artery graft flow-meter apparatus of the present invention
is shown. The coronary artery graft flow-meter apparatus 10 may
be inserted into a delivery line 12 for solution to be perfused
through a graft. The flow-meter apparatus 10 comprises a flow-meter
chamber 14 having an upper end 16 and a lower end 18. Flow-meter
chamber 14 preferably has a volume of 200 cubic centimeters (cc).
Upper end 16 has an inflow port 20 secured by a clamp 22 and lower
end 18 has an outflow port 24. Outflow port 24 is connected to a
pump 26 by means of flow tubing 28.
The flow-meter chamber 14 includes a collapsed plastic bag 30
which preferably has a volume of 160 cc positioned therein. Plastic
bag 30 is adapted to communicate via a port 32 with a volumetric
container 34. Volumetric container 34 is filled with whatever solution,
such as cardioplegia or cold solution, the surgeon desires, as long
as the same solution is present in the flow-meter chamber 14. Such
solution flows from volumetric container 34 to plastic bag 30 within
chamber 14 via flow tubing 36 through port 32. As described in detail
hereinafter, this flow mechanism provides a measurement of the flow
rate of the solution through the graft.
As shown in detail in FIGS. 2 and 3 plastic bag 30 within flow-meter
chamber 14 is filled and emptied by a multifenestrated tube 38 within
it so that the open end of bag 30 cannot be emptied first and collapse,
thereby shutting off the outflow and leaving the closed end of bag
30 without a way to be emptied. Chamber 14 further includes a fence
40 which holds back the plastic bag 30 so that it cannot expand
over the outflow port 24 of chamber 14 and shut it off.
Volumetric container 34 preferably has the same dimensions as the
flow-meter chamber 14. The preferred dimension is 2.times.2.times.50
cm.
As shown in FIG. 1 the flow-meter chamber 14 and the volumetric
container 34 communicate via flow tubing 36 at their lower ends
18 and 42 respectively. In the flow-meter chamber 14 the communication
goes completely into the multifenestrated tube 38 and the plastic
bag 30 around it, while in the volumetric container 34 the communication
permits free flow into and out of the container 34. The volumetric
container 34 additionally has an air vent 44 at its upper end 46
which is attached to an air filter (not shown).
Once the flow-meter chamber 14 has been filled with fluid and air
has been evacuated from the flow-meter chamber 14 the volumetric
container 34 can be filled and air vent 44 opened so that the fluid
from the volumetric container 34 is free to flow into the multifenestrated
tube 38 and the plastic bag 30 within the flow-meter chamber 14
and back again. There is an inflow port 48 at the upper end 46 of
the volumetric container 34 through which the container 34 is filled
by a Y-tube 50 the other part of which is attached to the inflow
port 20 of the flow-meter chamber 14. Just as the flow-meter inflow
port 20 the volumetric container inflow port 48 also is secured
by a clamp 52.
As shown in FIG. 4 the volumetric container 14 is fitted with
a bracket 54 on the side 56 facing the flow-meter chamber 14 so
that it can be firmly held to a positioning device 58. The flow-meter
chamber has a similar bracket 60 on the corresponding side 62.
As shown in FIGS. 5 and 6 the positioning device 58 holds the
volumetric container 34 on one side of it and the flow-meter chamber
14 on the other. When the positioning device 58 is rotated clockwise,
the volumetric container 34 is raised and the flow-meter chamber
14 lowered so that the apparatus 10 is in the flow-measuring position.
When the positioning device 58 is rotated counterclockwise, the
volumetric container 34 is lowered and the flow-meter chamber 14
is raised so that the fluid can be emptied more readily from the
plastic bag 30 back into the volumetric container 34.
Each bracket 54 60 is perforated at its upper and lower ends 64
65 66 and 67 to fit four pivots, respectively, secured with threaded
posts and wing nuts on two strong metal bars 72 74 with a washer
on each side of the bracket. These strong metal bars 72 74 are
attached to a positioning device 58 so that both the volumetric
container 34 and the flow-meter chamber 14 can be firmly held on
the positioning device 58 with washers and wing nuts.
As shown in FIG. 7 attached to each threaded post 68 70 is a
strong metal bar 72 74 perforated at each end to accommodate a
post, with a washer on each side of the metal bar. The upper metal
bar 72 that is attached to the upper part 64 of the bracket 54 of
the volumetric container 34 is attached at its other end to the
upper part 66 of the bracket 60 of the flow-meter chamber 14 and
the metal bar 74 attached to the lower part 65 of the bracket 54
of the volumetric container 34 is attached as its other end to the
lower part 67 of the bracket 60 of the flow-meter chamber 14.
Halfway between the perforations 76 77 78 79 on each metal bar
72 74 there are third perforations 80 81 which permits the metal
bars 72 74 to rotate on pivots 82 84 respectively. The pivots
82 84 for the two metal bars 72 74 are as far apart, one above
the other, as the perforations in the brackets, so that the metal
bars 72 74 the brackets 54 60 and the part 86 of the positioning
device 58 between the pivots describe parallelograms with variable
angles. In this manner, volumetric container 34 and the flow-meter
chamber 14 remain in an upright posture when they are raised or
lowered. One metal bar is fitted with a handle (not shown) so that
the metal bar can be rotated on the pivot, thereby alternately raising
the volumetric container and lowering the flow-meter chamber, and
vice versa.
The part 86 of the positioning device between the two pivots 82
84 is fitted on its back side with a bracket (not shown) to permit
it to be tightly fastened to a stand or to a pump-oxygenator so
that it will not tip or be knocked over by accident.
In practice, cardioplegia solution, with or without blood, or cold
solution, or pump solution, as desired by the surgeon, is used to
fill the flow-meter chamber 14 and air is evacuated via an air
vent from 16 or by inverting the chamber 14. The tubing 28 from
the outflow port 24 runs through the pump 26 and then is connected
to the proximal end of the graft in the usual fashion as is well
known to those of skill in the art. Cardioplegia or cold solution
is then perfused as known in the art, ideally at the patient's pre-surgery
mean arterial blood pressure. When a measurement is to be taken,
the inflow port 20 of the flow-meter chamber 14 is closed off with
the clamp 22. As the cardioplegia or cold solution, etc. is pumped
out of the flow-meter chamber 14 the solution from the volumetric
container 34 flows into the plastic bag 30 within the flow-meter
chamber 14. The rate of flow of this solution precisely corresponds
to the flow rate through the graft, and thus provides an accurate
measurement thereof.
The rate of flow from the volumetric container 34 can be assessed
visually, or with a variety of electronic or colorimetric devices
well known in the art. After each measurement, the flow-meter chamber
14 is refilled by opening the inflow port 20 of the flow-meter chamber
14 and raising the chamber 14 by means of positioning device 58
to empty the contents of the plastic bag 30 back into the volumetric
container 34. Should simultaneous flow rates through two grafts
be required, dual systems can be assembled using a second pump head.
Should the plastic bag 30 rupture, the solution from the volumetric
container 34 which is the same as is in the flow-meter chamber
14 will mix with the flow-meter chamber solution, thereby avoiding
problems as far as graft perfusion is concerned. Should the fluid
level in the volumetric container 34 fall too low, a sensor (not
shown) attached to the volumetric container 34 will alarm and automatically
turn off the pump 26 before air can enter the plastic bag 30 within
the chamber 14.
Sterility is assured by discarding the unit after each use. The
measuring or sensing device which clips on to the volumetric container
34 as well as the positioning device and the clamps can be removed
and reused. The apparatus 10 of the invention can be set up by a
pump technician before use and handled in the same way as the pump
tubing or coronary perfusion lines to ensure sterility.
The rate of flow through the graft is regulated by a servo mechanism
88 attached to the pump 26 which responds to a pressure sensing
device 90 in the line 92 immediately beyond the pump 26 and before
the graft.
The coronary artery graft flow-meter apparatus of the present invention,
when used properly as described above, provides a disposable, low-volume,
closed system which efficiently and safely provides an accurate
measurement of the solution flow rate through a coronary artery
graft.
The foregoing is intended as illustrative of the present invention
but not limiting. Numerous variations and modifications may be effected
without departing from the true spirit and scope of the invention. |