Surgical fluid suction accumulator and volume measurement device

An apparatus for minimizing trauma to a medical fluid while transporting the medical fluid from a surgical wound by reducing the air to fluid interface during transport. The apparatus includes a suction wand for collecting medical fluid and tubing for transporting the medical fluid to a reservoir. The reservoir repeatedly accumulates the medical fluid and discharges it in a bolus when a predetermined volume is achieved. The reservoir comprises a fluid inlet, a fluid outlet, and a gas outlet. A siphon is disposed inside the reservoir for removing the bolus of medical fluid once the predetermined fluid volume is accumulated. The siphon includes a first end for suctioning the medical fluid and a second end exiting the reservoir through the fluid outlet, thereby defining an external siphon length. A pump is attached to the second siphon end to provide suction to the system. A bypass line connects the reservoir, from its gas outlet, to the external siphon length thereby removing air from the reservoir and, thus, increasing the reduction of the air to fluid interface during transport of the medical fluid.

FIELD OF INVENTION 
The present invention relates to collecting and measuring surgical fluid 
during the course of a surgical procedure. More particularly, the present 
invention relates to minimizing trauma to blood, recovered and measured 
during surgery, so that it may be harvested for later use or returned to 
the patient. 
BACKGROUND OF THE INVENTION 
During a surgical procedure it is often desirable to recover blood from the 
surgical wound and return it to the patient or harvest it for later use in 
blood salvaging procedures. Blood is typically recovered by suctioning it 
from the surgical wound, using a suction wand, through a tubing set into a 
collection reservoir. Suction wands generally aspirate both air and blood 
causing a turbulent flow in the suction wand and numerous blood to air 
interfaces as the blood is transported through the tubing set to the 
collection reservoir, blood oxygenator, blood salvaging device or the 
like. This turbulent flow in the suction wand coupled with blood transport 
having many blood to air interfaces, has been found to be a major source 
of blood trauma, particularly during open heart surgery. Furthermore, 
blood exposed to air may coagulate and form clots, thus, becoming 
unsuitable for reinfusion to the patient or for later use in blood 
salvaging procedures. 
In the conventional system, this blood flow having many blood to air 
interfaces, must travel through a long tubing length before being 
collected in a collection reservoir, or processed by a blood oxygenator, 
blood salvage device or the like. Furthermore, in the conventional system 
the amount of suction applied to the suction wand typically remains 
constant throughout a surgical procedure. This constant suction does not 
account for the erratic and variable flow rate of patient blood losses 
during a surgical procedure; therefore, the same amount of suction is 
applied during low flow rates of patient blood losses as during high flow 
rates. Using a high amount of vacuum to suction blood during low flow 
rates may increase the amount of air aspirated into the tubing set along 
with patient blood. This may not only increase the turbulent blood flow, 
but may also increase the air to blood interface, thereby increasing the 
potential for blood trauma. 
It is, therefore, desirable to reduce the turbulence of blood flow in blood 
salvaging procedures. It is also desirable to reduce the distance that 
salvaged blood must travel in contact with air. Further, it is desirable 
to reduce the air to blood interface in blood salvaging procedures. 
SUMMARY OF THE INVENTION 
A significant aspect of the present invention is a device and method for 
reducing the surface area of blood to air interfaces in the blood 
collection lines used in blood salvaging during surgical procedures. 
Another significant aspect of the present invention is a method and device 
for reducing the distance that salvaged blood must travel while containing 
a significant quantity of air to blood interfaces. 
Another significant aspect of the present invention is a method and device 
for reducing the amount of air to blood interfaces in blood collection 
lines during blood salvaging. 
Another significant aspect of the present invention is method and device 
for measuring a rate of blood flow from a patient's surgical wound to the 
blood receiving reservoir. 
Another significant aspect of the present invention is a method and device 
for warning a medical care worker of excessive patient bleeding. 
Another significant aspect of the present invention is a method and device 
for measuring the volume of blood salvaged during a surgical procedure. 
Another aspect of the present invention is a device and method for reducing 
the turbulence of blood flow by reducing the amount of air aspirated with 
the blood from the surgical wound by controlling the amount of suction or 
vacuum applied to the system. 
In accordance with the above aspects the present invention provides a blood 
accumulator having a fluid collector connected to a reservoir by a tubing 
collector line. A siphon is disposed inside the reservoir. The siphon has 
a tubing end that extends below the reservoir's exterior and communicates 
with a vacuum source. An air bypass line connects the upper interior of 
the reservoir with external siphon tubing. 
The vacuum source creates suction or a vacuum in the reservoir and, 
therefore, in the fluid collector and tubing connector line. Blood and air 
are suctioned through the fluid collector and tubing connector into the 
reservoir. The blood accumulated in the bottom of the reservoir while air 
is drawn out of the reservoir by the bypass line. When the blood level 
reaches the top of the siphon, the blood is siphoned out of the reservoir 
as a single bolus having a continuous flow. The air to blood interfaces of 
prior art blood collectors are reduced because air is separated from the 
received patient blood and the blood is transported in large boluses. 
When the blood level reaches the top of the siphon, a fluid level sensor 
may be activated. The fluid level sensor reports each activation to a 
controller. The volume of blood contained in the reservoir when the fluid 
level sensor is activated is predetermined by the configuration of the 
reservoir. The controller may count the sensor activations over the course 
of a procedure and during given time periods to determine the total volume 
of blood processed and the rate at which blood is flowing from the patient 
to the reservoir. The controller may adjust the amount of vacuum or 
suction applied to the system, when the rate of patient blood flow to the 
reservoir decreases, thereby reducing the amount of air aspirated with 
blood by the fluid collector and, thus, reducing turbulent flow in the 
suction wand. 
The controller may be programmed to activate an alarm when the rate of 
patient blood flow to the reservoir exceeds a predetermined threshold. 
Similarly, the controller may be programmed to activate an alarm when no 
blood flow is detected over a predetermined time period indicating that 
the suction wand is not positioned correctly. 
Other objects of this invention will appear from the following description 
and appended claims, reference being had to the accompanying drawings 
forming a part of this specification wherein like reference characters 
designate corresponding parts in the several views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 schematically illustrates the blood accumulator 10 of the present 
invention. The blood accumulator comprises a fluid collector 12 for 
collecting or receiving blood or other biological fluids from a patient 
during a surgical procedure. The fluid collector 12 may comprise any one 
of the well known devices used for salvaging blood from a patient during 
surgery, including a suction wand. The fluid collector 12 is connected to 
a tubing connector 14 that transports the received blood to the fluid 
inlet 16 of the blood receiving reservoir 18. The tubing connector 14 may 
comprise a piece of tubing having a length of about twelve to eighteen 
inches. It is preferred that the tubing connector 14 comprise the shortest 
length that is practical for the blood salvage system design, thereby 
minimizing the distance blood must travel while having a large surface 
area of blood to air interfaces. Alternatively, the blood accumulator 10 
may be incorporated directly into the suction wand, to minimize the 
distance that blood is transported having numerous blood to air interfaces 
as will be discussed in more detail in FIG. 5. 
A siphon 20 is disposed in the interior 22 of the blood receiving reservoir 
18. The siphon 20 comprises a first tubing length 24, a top 26, and a 
second tubing length 28. The second tubing length 28 extends through the 
reservoir outlet 30 to the exterior of the reservoir thereby forming an 
exterior siphon length 32 which is disposed below the first siphon tubing 
length 24. It is important that the exterior tubing length 32 be disposed 
below the first siphon tubing length 24 for the siphon 20 to function, as 
will be discussed in more detail below. An end 34 of the exterior tubing 
length 32 is engaged by a vacuum source 36. The vacuum source may comprise 
a peristaltic pump (FIG. 1), a vacuum pump (FIG. 2), or any one of the 
other types of medical pumps well known by those skilled in the art. 
An air bypass line 38 connects an upper portion of the reservoir interior 
22 with the exterior tubing length 32. A first end 41 of the air bypass 
line 38 connects to the blood receiving reservoir 18 at the reservoir's 
air outlet 40. A second end 43 of the air bypass line 38 connects to the 
exterior tubing length 32 at a junction 42. It will be apparent to those 
skilled in the art that the air bypass line 38 may be disposed inside the 
reservoir having an end disposed above the top 26 of the siphon 20 and an 
opposing end connecting to the second tubing length 28. 
Where the vacuum source 36 is a peristaltic pump, it creates a vacuum in 
the exterior tubing length 32 which in turn creates a vacuum in the 
reservoir 18. The vacuum in the reservoir 18 creates a vacuum in the fluid 
collector 12 and the tubing connector line 14, thereby suctioning blood 
and other fluids from the surgical wound to the reservoir 18. The vacuum 
source 36 may draw the blood or biological fluid through a tubing set 44, 
as denoted by the direction arrow 46, to a storage reservoir (not shown). 
For example, in a cardiac bypass operation, the vacuum source 36 may draw 
fluid to a blood oxygenator reservoir (not shown) or to a cardiotomy 
reservoir (not shown). 
In blood salvage operations, the vacuum source 36 may be a vacuum pump 45 
as shown in FIG. 2. The vacuum pump 45 is connected to a storage reservoir 
47 by a tubing line 49. The vacuum pump 45 creates a vacuum in the storage 
reservoir, creating a vacuum in the external tubing length, in turn 
creating a vacuum in the blood receiving reservoir 18 which creates a 
vacuum in the fluid collector 12 for suctioning fluid from the surgical 
wound. The suctioned fluid is drawn by the vacuum pump 45 to the storage 
reservoir 47 where a peristaltic pump (not shown) may draw the blood 
through line 51 to a blood processor (not shown). 
Referring again to FIG. 1, a fluid level sensor 48 is affixed to an upper 
portion of the reservoir wall 50. The fluid level sensor 48 may extend 
through the reservoir wall 50 to the reservoir interior 22. The fluid 
level sensor 48 may not extend through the reservoir wall 50 where it is 
of a type that functions from outside the reservoir, such as an ultrasonic 
or optical sensor. The fluid level sensor 48 is positioned to detect a 
fluid level 52 of blood or biological fluid in the siphon 20 when the 
fluid level 52 reaches the top 26 of the siphon 20. The fluid level sensor 
48 may be an optical sensor, capacitive sensor, ultrasonic sensor or any 
one of the many non-invasive fluid level sensors well known in the art. 
The volume of fluid the reservoir 18 contains when the fluid level 52 
reaches the top 26 of the siphon 20 must be sufficiently large such that 
when the accumulated fluid is transported through the tubing 32 the 
surface area of air to blood interfaces is significantly reduced. It is 
preferred that the reservoir contain at least 5 milliliters when the fluid 
level 52 reaches the top 26 of the siphon 20. 
A controller 54 communicates with the fluid level sensor 48 and the vacuum 
source 36 through conventional electrical interconnects 56, 58. The 
controller may comprise one or more micro processors. The controller 54 
may further comprise an alarm 60. 
FIGS. 3 and 4 schematically illustrate the accumulator 10 when the fluid 
level 52 reaches the top 26 of the siphon 20 and shortly thereafter. As 
discussed above, when suction or a vacuum is applied to the external 
tubing length 32, mixed blood and air are in turn drawn through the fluid 
collector 12 (FIG. 1), through the tubing connector line 14 and into the 
reservoir 18 as denoted by the direction arrow 60. The blood and air 
separate in the reservoir 18, the blood accumulates in the bottom of the 
reservoir 18 while the air is removed from the reservoir 18 by the air 
bypass line 38 as denoted by the direction arrow 62. The air bypass line 
38 draws the air into the external tubing length 32, as denoted by the 
direction arrow 64, during the time in which the blood accumulates in the 
reservoir 18. 
Hydrostatic pressure forces the blood up the first siphon tubing length 24. 
When the blood level 52 reaches the top 26 of the siphon 20, thereby 
priming the siphon, the weight of the fluid bolus 66 causes the blood to 
travel down the second siphon tubing length 28 into the external tubing 
length 32 towards the vacuum source 36, as denoted by the direction arrow 
68, in a continuous flow. Because the reservoir 18 empties rapidly when 
the fluid level 52 reaches the top 26 of the siphon, air is pulled into 
the reservoir 18 rather than through the bypass line 38 into the external 
tubing length 32 during this time. Thus, the surface area of air to blood 
interfaces are reduced by the present invention. 
Once the fluid has exited the reservoir 18 in a bolus, the fluid level 52 
of the fluid remaining in the reservoir is below the tip 53 of the first 
siphon tubing length unless patient blood flow is very rapid. The blood 
continues to accumulate in and exit the reservoir 18, in the above 
described siphon cycles, as long as suction or a vacuum is applied to the 
system. Where blood flow from the surgical wound to the reservoir 18 is 
sufficiently rapid, blood will be removed from the reservoir 18 
continuously rather than accumulating and evacuating through the above 
described siphon cycle. 
Referring to FIGS. 1 through 3, the fluid level sensor 48 is activated 
every time the fluid level 52 reaches the top 26 of the siphon 20. The 
fluid level sensor 48 signals the controller 54 each time that it is 
activated. The controller 54 may measure the time t.sub.f it takes for the 
reservoir 18 to refill with fluid which is determined by measuring time 
between the release of the previous fluid level sensor 48 activation and a 
new activation. Because the fluid level sensor 48 is positioned to detect 
fluid in the top 26 of the siphon 20, and the siphon 20 remains full until 
the reservoir fluid level 52 drops below the siphon tip 53, the controller 
54 may measure the time t.sub.c it takes for the reservoir 18 to empty by 
measuring the time between a fluid level sensor 48 activation and release 
of the activation. The reservoir 18 contains a predetermined volume 
V.sub.a of blood when the blood fluid level 52 reaches the top 26 of the 
siphon 20 and activates the fluid level sensor 48. 
The controller 54 may calculate the total blood volume salvaged V.sub.t 
during a given procedure as follows: 
EQU V.sub.t =Q.sub.b (T.sub.f +t.sub.c) 
where 
Q.sub.b =rate at which blood is flowing from the patient to the reservoir 
18. 
The controller 54 may divide the predetermined reservoir volume V.sub.a by 
the time t.sub.f it takes the reservoir 18 to fill or refill to determine 
the rate Q.sub.b at which blood is flowing from the patient to the 
reservoir 18. If the controller 54 detects a change in rate at which blood 
is flowing into the reservoir 18, the controller 54 may instruct the 
vacuum source 36 to adjust the amount of vacuum or suction it is applying 
to the external tubing length 32. If the rate at which blood is flowing 
into the reservoir 18 increases, the controller 54 may instruct the vacuum 
source 36 to increase the amount of suction or vacuum it is applying. 
Conversely, if the rate at which blood is flowing into the reservoir 18 
decreases, the controller 54 may instruct the vacuum source 36 to decrease 
the amount of suction or vacuum, thereby decreasing the amount of air 
aspirated with blood into the fluid collector 12 and, therefore, 
decreasing the turbulent flow in the fluid collector 12. 
A value for a maximum threshold rate at which blood flows into the 
reservoir 18 may be programmed into the controller 54. The controller 54 
may activate an alarm 56 if this threshold rate is exceeded, thereby 
notifying an operator of excessive patient bleeding. Conversely, a minimum 
threshold rate may be programmed into the controller 54. If the controller 
54 does not detect at least this minimum rate of patient blood flow, the 
controller may also activate an alarm to notify an operator that the 
suction wand is not positioned correctly. 
Further, the controller 54 may optionally instruct a peristaltic pump 70 
associated with an anticoagulant line 72 to vary a rate at which the pump 
70 is delivering an anticoagulant, from an anticoagulant reservoir 74, to 
the blood receiving reservoir 18, in response to the patient blood flow. 
It will be apparent to those skilled in the art that the anticoagulant may 
be added to received blood in the blood collector, 12, connective tubing 
line 14, as well as, in the reservoir 18. The controller 54 may vary the 
anticoagulant delivery rate with detected blood flow as described in U.S. 
Pat. No. 5,378,227(1995) to O'Riordan et al., the disclosure of which is 
herein incorporated by reference in its entirety. 
FIG. 5 illustrates a fluid receiver 76 having a blood accumulator 10 
disposed in its interior. It will be apparent to those skilled in the art 
that the accumulator may be disposed in a fluid receiver 76 in any number 
of configurations. It is important, however, in this embodiment, that the 
first siphon length 28 be disposed at higher elevation than the external 
siphon length 32 in order for the siphon to function. 
Although the present invention has been described with reference to 
preferred embodiments, numerous modifications and variations can be made 
and still the result will come within the scope of the invention. No 
limitation with respect to the specific embodiments disclosed herein is 
intended or should be inferred.