Abstrict A urine flow meter including a toilet mounted collector is disclosed.
The collector has a mouth portion which is dimensioned to fit within
a toilet bowl and which has walls which slope downwardly and inwardly
to a neck portion. The neck portion extends downwardly from the
lower end of the mouth portion to receive urine directed into it
from the mouth portion. An aperture is formed in the neck portion
and a pressure sender has a lower end in communication with the
neck portion. An upper end of the pressure sender is above the neck
portion and is connected to a pressure transducer. Urine accumulates
in the neck portion until the flow rate into the collector equals
the flow rate out through the aperture. The accumulated volume of
urine in the neck portion produces an air pressure within the pressure
sender which is converted into an electrical signal by the pressure
transducer. The pressure transducer output signal is suitable to
be processed to provide critical urine flow data.
Claims I claim:
1. A disposable collector to be used in a urine flow meter for
measuring the flow rate of a stream of urine as it is voided into
the collector, comprising:
a lower neck portion having an open upper end and a substantially
closed lower portion, said lower portion having a first aperture
formed therein which is sized and positioned so that a typical urine
flow causes urine to accumulate in the neck portion above the first
aperture until the pressure at the first aperture causes a urine
flow out the neck portion equal to the urine flow into the collector;
an upper mouth portion having walls which slope downwardly and
inwardly from an open upper end to an open lower end, said lower
end of the mouth portion being coextensive with the upper end of
the neck portion to funnel the stream of urine into the neck portion;
a pressure sender having a lower end in communication with the
lower portion of the neck portion below the aperture and an upper
end above the neck portion suitable for connection to a pressure
transducer so that urine collected in the neck portion produces
an air pressure in the pressure sender which is sensed by the pressure
transducer; and
wherein the collector is dimensioned to be supported within a toilet
bowl so that urine collected in the neck portion drains from the
aperture into the toilet bowl.
2. The collector of claim 1 further comprising means for inhibiting
swirling of the urine in the neck portion.
3. The collector of claim 2 further comprising a second aperture
smaller than the first aperture formed in the neck portion below
the first aperture and above the lower end of the pressure sender,
said second aperture having a tube downwardly depending therefrom
on the exterior of the neck portion to lower the level of urine
in the neck portion to below the first aperture by siphon action
when there is no flow into the collector thereby reducing surface
tension effects of the urine at the first aperture.
4. A collector for a urine flow meter in which a pressure transducer
senses an air pressure within the collector which varies in accordance
with the volume of urine in the collector, comprising:
a mouth portion dimensioned to fit within a toilet bowl and having
walls which slope downwardly and inwardly from an open upper end
to an open lower end;
a neck portion connected to the lower end of the mouth portion
and extending downwardly therefrom, the neck portion having an open
upper end and a substantially closed lower portion, a first aperture
being formed in a sidewall of said lower portion;
a pressure sender having a lower end in communication with the
lower portion of the neck portion and an upper end above the neck
portion suitable for connection to the pressure transducer so that
a urine flow entering the mouth portion accumulates in the neck
portion and produces the air pressure within the pressure sender;
and
a second aperture smaller than the first aperture formed in the
neck portion below the first aperture and above the lower end of
the pressure sender and having a tube downwardly depending therefrom
on the exterior of the neck portion to lower the level of urine
to below the first aperture when there is no flow into the collector
thereby reducing surface tension effects of the urine when it is
at the level of the first aperture.
Description FIELD OF THE INVENTION
This invention relates to urine flow meters and particularly to
a urine flow meter having a toilet mounted collector.
BACKGROUND OF THE INVENTION
Diagnosis of urological disorders is often facilitated by a patient's
urine flow rate data. Urological disorders such as an obstruction
in the lower urological tract or neurotic bladder can be detected
by studying the patient's urine flow rate as it varies from the
beginning of voiding to the end and the total volume of urine voided.
This data can be compared to the mean data for an individual of
the same sex and age to help determine the degree of urethral stricture.
Urine flow data is also useful in diagnosing prostrate enlargement.
Prostrate enlargement usually occurs gradually with no noticeable
impairment to the patient. Merely observing the patient void will
usually not enable the urologist or physician to accurately assess
the degree of prostate enlargement. However, by observing histograms
of the urine flow, the urologist or physician can usually detect
the degree of prostrate enlargement and the necessary procedures
to be undertaken to correct the disorder. In addition, post-operative
urine flow data provides an excellent way of assessing the benefit
achieved by surgery.
Several different types of urine flow meters for providing urine
flow data are presently commercially available. Examples of a mechanical
urine flow meter for enabling manual measurement of urine flow are
found in U.S. Pat. Nos. 4099412 4200112 4241017 4000649
4085616 4301813 and reissue patent 30607. These mechanical
urine flow measuring devices usually comprise a container having
a graduated scale for indicating the volume of urine within the
container. Urine flow is detected by manually observing the change
in volume as the patient voids into the container. These devices
therefore require that either a physician, a nurse or a technician
observe the patient void into the container. While a privacy screen
is usually provided between the patient and the observer, the patient
may still exhibit distress or embarassment knowing that his or her
voided stream is being observed.
To overcome this disadvantage, electrical urine flow meters for
providing urine flow data have been developed. For example, U.S.
Pat. No. 4187722 discloses a urine velocity measuring device including
a urine flow receptacle having a paddle wheel journaled therein.
The paddle wheel is mechanically linked to a generator which produces
an output voltage which is displayed on a volt meter. The velocity
of the urine stream impinging on the paddle wheel determines the
paddle wheel velocity and therefore the output voltage of the generator.
U.S. Pat. No. 4051431 discloses another device for measuring
a urine flow electrically. The urine flow meter disclosed in this
patent includes a urine receiving receptacle which has a pair of
parallel spaced-apart rods or strips disposed therein. The rods
or strips are electrically connected to a capacitance sensing circuit.
As the volume of urine within the receptacle increases, the capacitance
between the rods also increases so that by measuring the rate of
change of the capacitance, an indication of the urine flow may be
obtained.
Both of the above described electrical urine flow meters require
a high degree of maintenance. Since urine contacts components of
each of the meters, those components must be cleaned following each
use. Therefore, a need exists for a low maintenance electrical urine
flow meter.
SUMMARY OF THE INVENTION
The invention provides a urine flow meter including a toilet mounted
collector. The collector has a mouth portion which is dimensioned
to fit within a toilet bowl and which has walls which slope downwardly
and inwardly from an open upper end to an open lower end. A neck
portion extends downwardly from the lower end of the mouth portion
and has a substantially closed lower portion. An aperture is formed
in the lower portion of the neck portion and a pressure sender is
in communication with the lower portion of the neck portion. The
end of the pressure sender opposite from the neck portion is above
the neck portion and is suitable for connection to a pressure transducer.
The mouth portion directs urine into the neck portion where the
urine accumulates. The accumulated volume of urine in the neck portion
produces an air pressure within the pressure sender which is suitable
to be processed to provide critical urine flow data. The aperture
allows the urine to exit to the toilet bowl at a rate which is dependent
upon the volume of urine in the neck portion.
A pressure transducer is connected to the upper end of the pressure
sender and provides an electrical signal which is proportional to
the air pressure within the pressure sender. A processor is connected
to the pressure transducer for converting the pressure transducer
output signal into a flow rate signal. The flow rate signal can
be further manipulated and/or output means provided for displaying
the resulting data.
The invention provides an improved urine flow meter which enables
accurate urine flow rate measurement. Much of the anxiety that a
patient may have had with prior art mechanical urine flow meters
is relieved because the urine collector of the invention is mounted
within a toilet. This not only obviates the need for an observer
of the voiding process, but simulates natural voiding since it is
mounted in a toilet.
The invention also provides a urine flow meter which is easy to
maintain. A collector for a urine flow meter of the invention can
be inexpensively manufactured from suitable plastic materials since
it has no moving or electrically conductive parts. Since it is inexpensive,
it can be disposed after each use thereby alleviating the cleaning
difficulties associated with prior art flow meters.
Other objects and advantages of the present invention will become
apparent from the following detailed description and drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side plan view of a urine flow meter constructed in
accordance with the present invention;
FIG. 2 is a perspective view of a toilet mounted collector for
the urine flow meter of FIG. 1;
FIG. 3 is a sectional view taken along the plane of line 3--3 of
FIG. 2;
FIG. 4 is a detail view partially in section of the lower portion
of the collector of FIG. 2;
FIG. 5 is a flow chart for the processor of FIG. 1; and
FIG. 6 is a view taken along the plane of line 6--6 of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 a urine flow meter 10 of the present invention
includes a collector 12. The collector 12 has a funnel shaped mouth
portion 13 which is dimensioned to fit within a toilet bowl 14.
The mouth portion 13 has walls which slope downwardly and inwardly
from an open upper end to an open lower end. While the mouth portion
13 shown is frusto-conically shaped, any mouth portion with walls
which slope downwardly and inwardly could be employed in the collector
12. A flange 16 circumscribes the periphery of the upper end of
the mouth portion 13 so that the collector may be supported by a
rim 17 of the toilet bowl 14. Alternatively, a separate frame (not
shown) could be employed to support the collector 12 within the
toilet bowl 14.
A circular cylindrical neck portion 18 extends downwardly from
the lower end of the mouth portion 13. The lower end of the neck
portion 18 is closed and the lower portion of the neck portion is
provided with a triangular-shaped aperture 22 (FIG. 6). A bleeder
aperture 24 which is much smaller than the aperture 22 is located
slightly below the level of the aperture 22 and is in communication
with one end of a short downwardly depending tube 25. A pressure
sender 28 which may be nothing more than an air filled tube, is
in communication with the lower portion of the neck 18 preferably
below the levels of the apertures 22 and 24. The pressure sender
28 extends upwardly above the neck portion 18 and has an end 29
which is suitable to be connected to a pressure transducer 30.
While the preferred embodiment disclosed has two apertures 22 and
24 it is not necessary that two apertures be provided to practice
the invention. The reason that the aperture 24 is provided is to
allow a very small amount of urine to exit therethrough to reduce
the surface level of the urine in the neck 14 to being below the
level of the aperture 22. Surface tension effects at the level of
the aperture 22 can cause somewhat erratic flow rate measurements.
To alleviate these effects, the aperture 24 is positioned below
the aperture 22 is much smaller than the aperture 22 and is provided
with the downwardly depending tube 25. The tube 25 draws the level
of the urine within the neck 18 down by siphon action to below the
level of the aperture 22 upon the cessation of flow into the collector
12 to alleviate these surface tension effects. However, in some
circumstances, these surface tension effects may not be apparent
or may be negligible so that a bleeder aperture 24 is not necessary.
Also, the aperture 22 need not be triangular. Depending upon the
application, it could be almost any shape. The preferred embodiment
employs a triangular shaped aperture 22 merely because that shape
was found satisfactory in practice. Similarly, the neck portion
18 need not be circular cylindrical.
The mouth portion 13 is provided as an easy target for a person
voiding. A number of louvers 31 extend across the upper end of the
mouth portion 13 as best illustrated in FIGS. 2 and 3. The louvers
31 are at an angle of about 60.degree. with the flat surface of
the flange 16 and serve to prevent urine from splashing out of the
mouth portion 13 as a patient voids into the collector. The mouth
portion 13 is also provided with a number of ridges 32 which extend
radially inwardly along the conical walls of the mouth portion 13.
The ridges 32 prevent the urine from swirling within the mouth portion
13 to prevent any centrifugal effects upon the level of urine in
the neck portion 18.
Urine entering the mouth portion 13 is directed down into the neck
portion 18 and accumulates therein. The combined areas of the apertures
22 and 24 are such that a typical urine flow causes the level of
urine within the neck portion 18 to rise even after the level has
surpassed the levels of the apertures 22 and 24. This is the case
even though some of the urine will exit the apertures 22 and 24.
The instantaneous flow rate out the apertures 22 and 24 will be
determined by the instantaneous height of urine within the neck
portion 18. This is because a certain height of urine within the
neck portion 18 will produce a certain pressure at the level of
each aperture 22 and 24. As the height of urine within the neck
portion 18 increases, so does the pressure at the level of each
aperture. This pressure increase causes the flow rate out each aperture
to increase. When the height of urine has reached a level which
causes the combined flow rates out the apertures 22 and 24 to equal
the patient's urine flow rate into the collector 12 the level will
stop rising and will remain constant at a steady state level. As
noted, when the level of urine within the neck portion 18 is at
a steady state level, the flow rate into the collector 12 equals
the flow rate out.
The relationship between the flow rate in, the flow rate out, and
the accumulated volume within the collector 12 is determined from
a simple mass balance. Specifically, this relationship is that the
flow rate in equals the flow rate out plus the rate of change of
the accumulated volume of urine within the collector 12. Symbolically,
this relationship is represented as follows:
where Flow.sub.in is the patient's average urine flow rate into
the collector 12 over a time interval from t.sub.1 to t.sub.2 Flow.sub.out
is the average flow rate out of the collector 12 over the same interval,
.DELTA.V is the change in volume of accumulated urine within the
collector 12 from t.sub.1 to t.sub.2 and .DELTA.t is the time interval
which equals t.sub.2 minus t.sub.1.
With the pressure transducer 30 sealed over the end 29 of the pressure
sender 28 some of the urine accumulating in the neck 18 will enter
the sender 28 and will compress the air therein to cause the air
pressure within the sender 28 to rise. The instantaneous pressure
within the sender 28 will be determined by the instantaneous height
of urine within the neck portion 18. Also, any given height of urine
within the neck portion 18 will be associated with a certain volume
of accumulated urine within the collector 12 including the volume
within the neck portion 18 and the relatively small volume within
the pressure sender 28. Note that since a certain height within
the neck portion 18 is associated with a certain air pressure within
the sender 28 a certain accumulated volume within the collector
12 and with a certain flow rate out of the collector 12 a given
air pressure within the pressure sender 28 can be directly associated
with a certain volume of accumulated urine in the collector 12 and
with a certain flow rate out the collector 12 to determine the flow
rate into the collector 12.
The pressure within the pressure sender 28 which is associated
with a certain accumulated volume within the collector 12 and with
a certain flow rate out of the collector 12 can be determined either
experimentally or analytically. However, since the air in the pressure
sender 28 is a compressible fluid, the analytical equation relating
the air pressure to the accumulated volume of urine in the collector
12 and to the flow rate out of the collector 12 is somewhat complicated.
On the other hand, the air pressures associated with various accumulated
volumes of urine and flow rates out can be easily determined experimentally.
To associate air pressures within the sender 28 with accumulated
volumes of urine within the collector 12 and with urine flow rates
out of the collector 12 a known flow rate of urine or liquid with
a comparable density would be introduced into the mouth portion
13. When the height of accumulated urine within the neck portion
18 reached the steady state level, the accumulated volume in the
collector 12 and air pressure within the pressure sender 28 would
be measured and recorded in a table to correlate them with the known
flow rate. This procedure could be repeated for many different known
flow rates into the neck portion 18 to provide a table of associated
accumulated volumes, pressures and flow rates. Since the flow rate
into the collector 12 equals the flow rate out when the urine in
the neck portion 18 is at the steady state level, the table can
be used to associate an instantaneous pressure within the pressure
sender 28 with a certain accumulated volume of urine within the
collector 12 and with a certain flow rate out of the collector 12
at the same instant in time regardless of whether the accumulated
urine is at a steady state level.
The pressure transducer 30 provides an electrical signal in accordance
with the air pressure in the pressure sender 28. The transducer
30 should be capable of following the air pressure within the sender
28 to provide an instantaneous indication thereof. Either gauge
or absolute pressure can be sensed by the pressure transducer 30.
However, it is preferable for the transducer 30 to sense gauge pressure.
This is because atmospheric pressure acts on the urine in the neck
18 so that gauge pressure, which is the difference between the pressure
in the sender 28 and atmospheric pressure, is a truer indication
of the pressure attributable to the height of urine within the neck
18. If absolute pressure were sensed, the atmospheric pressure would
have to be separately measured and subtracted from the absolute
pressure to yield the pressure attributable to the height of urine
in the neck 18.
A transducer 30 which was found suitable in practice is the transducer
sold under the trade designation Microswitch #142PC01G. This transducer
has a measuring port 31 and a gauge port 32. To measure gauge pressure,
the measuring port 31 is connected to the end 29 of the sender 28
and the gauge port 32 is left open to the atmosphere.
The output signal of the transducer 30 could be displayed and compared
to the table to determine the flow rate out of the collector 12
and the volume within the collector 12 at times t.sub.1 and t.sub.2.
The mass balance explained above could then be applied to determine
the average flow rate into the collector 12 over the time interval
from t.sub.1 to t.sub.2. This could be done for a number of time
intervals and the resulting flow rates plotted to yield a histogram
of the flow rate. The histogram could then be studied to yield valuable
information about the urine flow, or it could be further manipulated
to yield other data.
However manual processing of the pressure transducer output signal
into a flow rate or other data would be tedious and time consuming.
For this reason, a processor 35 is provided to manipulate the pressure
transducer output signal into a more useful form. The processor
35 includes an analog to digital converter 36 a central processing
unit 37 and a digital to analog converter 38. The pressure transducer
30 output signal is input to the analog to digital converter 36.
The analog to digital converter converts the pressure transducer
output signal into a digital signal which is suitable to be input
to the central processing unit 37. The central processing unit 37
is programmed to convert the digitized pressure signal into a flow
rate or other data and to output the data to the digital to analog
converter 38. The digital to analog converter converts the digital
flow rate signal into an analog signal which is suitable to be input
to a remote printer 40 to provide a histogram of the flow rate and/or
other data.
A flow chart of a program for converting the air pressure into
a flow rate is given in FIG. 5. The preferred processing technique
of FIG. 5 employs a central processing unit 37 which has an internal
clock which can generate a read signal at set intervals .DELTA.t
such as the microcomputer sold under the trade designation Intel
8051. The processing unit is programmed to await the signal from
the internal clock to begin the portion of the program wherein the
pressure signal is read and processed into the flow rate. After
initializing all registers, the first step in this portion of the
program would be to generate an enable signal to be carried by an
enable line 41 to the analog to digital converter 36. The analog
to digital converter 36 converts the pressure signal from the transducer
30 into a digital signal which is carried by a data bus 42 to the
central processing unit 37 where it is read.
The central processing unit 37 then converts the pressure signal
into a volume of urine within the collector 12 and into a flow rate
out of the collector 12. If a table compiled as previously explained
is used, the experimentally determined pressure, accumulated volume,
and flow rate out data is stored in associated memory addresses.
The processor compares the input pressure value to the stored experimental
pressure values and stores the memory address of the experimental
pressure value which is closest to the input pressure value. The
processor then goes to the associated accumulated volume and flow
rate out addresses to determine the accumulated volume of urine
within the collector 12 and the flow rate out of the collector 12
respectively. These simple processing techniques are symbolized
by the box labeled TABLE in the flow chart in FIG. 5.
Returning to the main portion of the flow chart in FIG. 5 the
accumulated volume and flow rate out are stored. Next, the average
flow rate out for the time interval since the last pressure reading
is calculated. This is done simply by adding the last obtained flow
rate out to the most recently obtained flow rate out and dividing
the sum by two. The average flow rate out is then stored. The next
step of the program is to calculate the average rate of change of
the accumulated volume of urine in the collector 12 over the time
interval since the last pressure reading. This is done by subtracting
the last obtained volume from the most currently obtained volume
and dividing the difference by the time interval. Adding the average
rate of change of the accumulated volume of urine in the collector
12 to the average flow rate out yields the average flow rate in
for the time interval between the two most current readings of the
air pressure. The average flow rate in and the time of the reading
are then stored.
The average flow in and the time of the most current reading are
displayed via the digital to analog converter 38. The central processing
unit 37 generates an enable signal which is carried by an enable
line 44 to the digital to analog converter 38. The digital to analog
converter 38 then reads the digitized flow in and time signals from
the data bus 42 and converts them into analog signals to be output
to the remote printer 40. Preferably, the output of the remote printer
40 is in the form of a graph with the vertical axis as the average
flow in and the horizontal axis as time.
After the display step, the program checks to see if the average
flow rate in equals 0. If the flow rate in equals 0 that is, if
there is no flow in, it may indicate that urination has ceased so
that it is desirable to stop processing. To this end, a no flow
timer is incremented with .DELTA.t. If the elapsed time of the no
flow timer has exceeded a certain maximum period, then the program
stops. If it has not exceeded that period, the processor returns
to await another read signal from the clock. This way, a momentary
interruption in urine flow will not result in stopping the processor.
If the average flow rate in is not equal to 0 the no flow timer
is initialized and the processor returns to await another read signal
from the clock.
The resulting flow rate data could be processed to yield other
data. For example, the flow rate in and time data could be integrated
to yield the total volume of urine voided by the patient. Also,
the starting time of voiding could be subtracted from the ending
time to yield the total time of voiding. Other quantities such as
the peak flow, the time of the peak, and the average flow could
also be determined and output.
A urine flow meter of the present invention has several advantages
over prior art urine flow meters. First, the invention reduces the
level of patient anxiety during a urine flow test. Since the patient
is accustomed to voiding into a toilet, the patient will suffer
less anxiety when voiding into the collector 12 held within the
toilet 14 than would be the case were the patient to void into a
separate receptacle of a prior art urine flow meter.
Second, little if any maintenance is required of a urine flow meter
of the invention. A collector 12 for the invention can be inexpensively
molded from a resin such as polyethylene so that it can be disposed
of after each use. Furthermore, urine never contacts the non-disposable
components of the invention such as the pressure transducer 30 so
that they need not be cleaned after each use.
Additionally, the invention facilitates the taking of a urine sample.
By disconnecting the pressure sender 28 from the pressure transducer
30 urine may be sucked from the neck portion 18 by a vacuum pump
(not shown).
Numerous modifications and variations of the preferred embodiment
will be apparent to those skilled in the art which will result in
flow meters which embody the invention. Therefore, it is not intended
that the invention be limited by the scope of the preferred embodiment
described and illustrated herein, but by the claims which follow. |