Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR MEASURING ARTERIAL
AND VENOUS BLOOD FLOW IN BODY APPENDAGES
FIELD OF THE INVENTION
The present invention is directed to a non-invasive
method and apparatus for measuring arterial and venous blood flow
in body appendages. The present invention is also directed to a
non-invasive method and apparatus for measuring penile tumescence
as a function of arterial and venous blood flow in the penis and
penile rigidity as a function of suprasystolic intra-cavernosal
pressure. These measurements are performed to make a diagnosis
in the field of erectile dysfunctions. Since every normal adult
male experiences erections during rapid eye movement sleep, the
measurements are preferably made during the patient's sleep, but
can also be performed when the patient is awake for diagnosis and
treatment.
BACKGROUND OF THE INVENTION
Measurement of nocturnal penile tumescence, hereinafter
referred to as NPT, has been widely used to establish a
differential diagnosis between organic impotence and psychogenic
impotence. Patients with organic impotence will have no
erections either when awake or during rapid eye movement sleep,
while psychogenic patients will experience erections during sleep
but not while awake.
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Measurement of NPT is usually performed with the help
of a plethysmograph. This device comprises a loop-shaped
silicone elastomer tubing filled with mercury. The tubing is
positioned around the penis of the patient and is connected to an
electrical circuit. Any change in the circumference of the penis
causes stretching of the silicone tubing which in turn triggers a
variation in the electrical resistance of the mercury filling.
The electrical circuit will measure this change in resistance
which can then be translated into a measure of the increase in
penile circumference. This measurement allows one to determine
penile tumescence.
However, while the plethysmograph enables the
measurement of penile tumescence, it does not provide a measure
of penile rigidity which is important in determining whether
vaginal penetration is possible. Penile rigidity is a function
of the pressure inside the corpus cavernosum. Measurement of
this pressure is sufficient to determine whether vaginal
penetration is possible.
Patent number 4,747,415 describes a device for
measuring intra-cavernosal pressure, hereinafter referred to as
ICP. This device comprises a cuff including a non elastic band
having one of its faces entirely covered with a plastic container
filled with a liquid. The non elastic band is wrapped around the
penis of the patient with the liquid container in direct contact
with the penis. A pressure transducer is mounted in direct
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communication with the liquid inside the plastic container for
sensing the pressure of the liquid. An electronic device is
provided for amplifying the pressure signal given by the
transducer and for recording and displaying this pressure. In
use, any erection of the penis causes an increase in ICP which in
turn compresses the liquid inside the container held in position
by the non expandable cuff. The pressure recorded is perfectly
correlated with the ICP.
During an erection, the corpus cavernosum fills up with
blood. In the first phase, its volume will increase until it
reaches its maximum. This is known as tumescence, characterized
by subsystolic pressure. In the second phase, known as rigidity,
ICP will rise to suprasystolic pressure levels. The corpus
cavernosum comprises an arterial inflow and a venous outflow. For
ICP to rise, it is necessary to have an increase in inflow
simultaneously with a decrease in outflow.
When measurement of the ICP of the patient reveals an
organic impotence, it remains to determine whether this is due to
the absence of increase in inflow (arterial pathology) or absence
of decrease in outflow (venous leak). Knowledge of the inflow,
for example, would allow one to determine the origin of the
organic impotence.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an
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apparatus and method for non invasive measurement of arterial and
venous blood flow.
It is a further object of the present invention to
provide a non invasive method and apparatus for measuring both
ICP and changes in arterial and venous flows of the corpus
cavernosum in order to distinguish between organic and
psychogenic impotence and to determine, in the case of organic
impotence, whether this is due to an arterial pathology or a
venous leak.
Further objects and advantages of the present invention
will become evident from the following drawings and description.
To this effect, the present invention provides an
apparatus for measuring arterial and venous blood flow. The
apparatus comprises:
a cuff including a flexible, non elastic band, one face
of which is covered with at least one plastic container capable
of being filled with a fluid,
means to position, close and firmly hold the non
elastic band around a body appendage of the patient, such as the
penis, so that, in the closed position, the container will remain
on the inside of the cuff,
a pressure transducer in direct communication with the
fluid inside the container to measure its pressure, and
electronic means to modify the sensitivity of the
pressure transducer and to amplify and/or display the signals
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generated by the transducer.
The apparatus further comprises a photoplethysmograph
having a probe attachable to the container so that the light beam
emitted by the probe is directable either toward the container
and the fluid therein or toward the appendage around which the
cuff is positioned. Also included are electronic means to modify
the sensitivity of the photoplethysmograph and to amplify and/or
display the signals generated thereby.
The method of this invention for measuring penile
rigidity of the patient comprises the following steps:
prior to use, filling the at least one plastic
container covering the internal face of the cuff with a fluid,
liquid or gas,
attaching the photoplethysmography probe to the outside
of the container on the face opposite the non elastic band,
positioning the cuff around the non erect penis of the
patient with the fluid filled plastic container and the
photoplethysmography probe in direct contact with the penis,
measuring the fluid pressure inside the plastic
container,
during pressure measurement, activating the
photoplethysmography probe to emit a light beam and measuring the
reflected light using the photoelectric cell of the same probe,
amplifying, record~ng and/or displaying the
measurements performed.
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The invention also provides a method of obtaining a
curve of arterial blood flow changes which comprises the
following steps:
recording the pulse signal generated by the
photoplethysmography probe during the flaccid stage and then
during tumescence for measured pressures inferior to a preset
value,
recording the pulse signal generated by the pressure
transducer for pressures greater than the previous preset value,
evaluating the pulse using the surface area under the
curve obtained from the two previous recordings in order to
obtain a curve of arterial blood flow changes.
The present invention further provides a method for
obtaining the curve of venous blood flow changes whereby the
presence of a venous leak may be determined. The method of
obtaining this curve comprises the following steps:
obtaining the curve of arterial blood flow changes as
described above,
recording the pressure transducer signal for pressures
below the preset pressure value,
calculating from the previous pressure curve and the
curve of arterial blood flow changes, using fluid mechanics laws,
the changes in venous blood flow in order to obtain their curve.
If the arterial inflow increases without an increase in
pressure and volume, it can be deduced that the inflow is equal
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to the outflow which allows one to establish that there is no
blood retention in the penis.
Preferably, the method includes the continuous
measurement of pulse frequency, duration and amplitude of ICP
changes, as well as the measurement of arterial blood flow
changes. It is then possible, from these measurements, to
classify each patient in a group. To provide this
classification, the following steps are added to the method:
measurement of fluid pressure according to the
described method,
plotting of the obtained curve,
identification for each tumescence period of a pressure
plateau corresponding to the vascular phase and of pressure peaks
corresponding to the muscular phase,
evaluation of the surface area of the plateau and the
surface area of the peaks corresponding to the plateau,
transfer of these results into a diagram with the
plateau surface area on the X-axis and the surface area of the
peaks on the Y-axis, or inversely,
plotting of a curve with time on the X-axis and plateau
pressure as well as maximum peak pressures on the Y-axis.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view of a first embodiment of the
apparatus of the invention.
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Fig. 2 is a schematic view of a second embodiment of
the apparatus of the invention.
Fig. 3 is a schematic view of a third embodiment of the
apparatus of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Several embodiments of the apparatus are proposed. In
a first embodiment, shown in Fig. 1, the cuff comprises one
plastic container which is preferably filled with water. The use
of water or another liquid is optimal for pressure measurement.
In a second embodiment, shown in Fig. 2, the cuff comprises two
containers, one filled with water in direct communication with
the pressure transducer, the other filled with air and maintained
at constant pressure and to the outside of which the
photoplethysmography probe is attached on the face opposite the
non elastic band. Although water and air are the preferred
fluids for use in the apparatus, other fluids suitable for
pressure measurement may be used.
The invention will be well understood by following the
description below with reference to the drawings shown herein.
These drawings are non restrictive examples of apparatus which
conforms to the invention and provide means for implementation of
the methods described herein.
The first embodiment, an apparatus to measure ICP and
blood flow in the penis of a patient, is represented in Fig. 1.
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The apparatus comprises a penile cuff 1 including a non elastic
band 2 with one of its faces covered with a transparent plastic
container 3 capable of being filled with a fluid, such as water,
using a syringe 4. A stopcock 5 is mounted between the syringe 4
and the container 3 in order to be able to remove the syringe 4
once the container 3 is filled. A pressure transducer 6 measures
the pressure inside the container 3. A pressure tubing line 7
links the pressure transducer 6 to the container 3.
The signals measured by the pressure transducer 6 are
amplified and transmitted to a computer 8 which records them and
displays them on its screen. The computer 8 also allows for
numerical treatment of these signals in order to analyze them and
produce a statistical analysis. A printer 9 allows printing of
the curves displayed on the screen as well as of all numerical
results.
The probe 10 of a photoplethysmograph 11 is attached to
the outside of the container 3 on the face opposite the band 2.
The probe 10 comprises a photo-emitting diode and a photoelectric
cell. A light beam is emitted by the diode and the reflected
beam is captured by the photoelectric cell. The probe 10 is
preferably mounted so that the emitted light beam will be
directed toward the skin of the appendage on which the cuff 1 is
positioned. However, in some cases better measurements are
obtained when the probe 10 is mounted so that the light beam is
directed toward the cuff 1. Accordingly, it is considered to be
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within the scope of this invention to mount the probe 10 in
either fashion.
The signal generated by the photoelectric cell is
amplified, recorded into the memory of the computer 8 and can
then be displayed on the computer screen and/or printed on the
printer 9.
Every erection of the penis is the consequence of an
increase in ICP and, with the plastic container being firmly held
around the penis, this increase in pressure compresses the fluid
inside the container. Therefore, the measurement of the pressure
of the fluid allows one to know the ICP which is directly related
to the rigidity of the penis.
The photoplethysmograph is used to measure blood flow.
Such devices have been widely used to measure blood flow in
capillaries under the skin. However, the most interesting blood
flow to measure here is arterial flow inside the corpus
cavernosum. The latter is surrounded by a thick membrane, the
tunica albuginea, which can hardly be crossed by the light of a
photoplethysmograph. Some measurements have revealed that the
photoplethysmograph can measure penile blood flow when the light
beam of the photoplethysmography probe is directed toward the
skin. Surprisingly, measurements have also been found possible
when the light beam of the photoplethysmography probe is directed
toward the liquid filled container. In some instances these
measurements are better than those obtained when the light is
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directed toward the skin. In this manner, a measurement of the
global penile pulse and, therefore, of the global arterial flow
of the penis, is obtained.
To carry out measurements of penile rigidity, the
plastic container 3 is filled with water and the cuff 1 is then
wrapped around the penis of the patient (not shown), while non
erect, so that the plastic container 3 and the
photoplethysmography probe are in direct contact with the penis.
When erection occurs, pressure inside the corpus
cavernosum increases. the container 3 is held between the penis,
which exerts a pressure, and the non elastic band 2. The
pressure inside the corpus cavernosum is transmitted to the
container 3 which is compressed. During a predetermined period,
a complete sleep period for example, the pressure transducer 6
measures pressure changes which are amplified and sent to the
computer 8 for analysis.
Alternatively, the measurements taken by the pressure
transducer 6 and the photoplethysmograph 11 may be stored by a
portable recording unit 14 for later downloading to the computer
8. In this manner, the apparatus may be made portable and the
patient may use the system at home to record nocturnal
measurements and return the recording unit 14 to his doctor for
subsequent downloading and analysis. In a further alternative,
using common modem technology, the data may even be stored in the
recording unit 14 and then transferred via modem to the doctor's
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office.
Simultaneously, the photoplethysmograph 11 measures
changes in arterial blood flow.
In the preferred manner of use, i.e., with the light
emitted toward the skin, the photoplethysmograph provides a
signal resulting from two physical phenomena:
absorption of emitted photons, mainly by red
blood corpuscles, which absorption varies
with the level of oxygenation of the red
blood corpuscles, which changes during the
erection, and
reflection of the emitted photons by the
walls of the vessels and tissues.
The light beam of a photoplethysmograph ordinarily has
a low intensity and can only penetrate through a few millimeters
of tissue. Therefore, it cannot ordinarily reach the internal
face of the tunica albuginea and measure the blood flow in the
cavernous artery within the tunica albuginea.
Surprisingly, it has also been noticed that by
directing the light beam externally, i.e., toward the container 3
and the penile cuff 1, the photoplethysmograph 11 generates a
signal which is synchronous with the penile pulse.
Variations of the signals generated by the
photoplethysmograph are most likely linked to changes in the
thickness of the container. These changes in thickness are more
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obvious at the beginning of the erection when ICP is low and the
penis is still soft and therefore compressible.
After an increase in pressure in the corpus cavernosum,
tissues are no longer compressible and changes in pulse amplitude
cannot be transmitted to them anymore. Thus, the
photoplethysmography probe 10 no longer records any variation.
On the other hand, the pressure transducer continues to record
the pressure changes.
Thus, the invention provides a means to obtain the
curve of changes in penile arterial blood flow, in particular
during an erection. This curve can be obtained from two sources:
the photoplethysmograph 11 during tumescence
while ICP is low and inferior to a preset
pressure, and
the pressure transducer 6 which records the
pulse on top of the pressure.
These two curves are analyzed and the evaluation of the surface
area under the curves obtained provides a means to calculate the
arterial blood flow curve.
From this curve, it is also possible to get the curve
of changes in venous blood flow. It is then necessary to measure
ICP even for pressures inferior to the preset pressure value.
Using the two curves obtained, ICP and changes in arterial
pressure, and classical laws of fluid mechanics, changes in
venous flow may be calculated and their curve plotted.
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Knowledge of changes in venous blood flow provides
information which can be directly exploited to assess venous
leaks. Using this method it is also possible to identify
pressure plateaus corresponding to tumescence and pressure peaks
linked to contraction of the ischiocavernosus muscles.
Using computer systems with analysis of the signal, it
is then possible to measure the surface area of the plateaus, the
surface area of the peaks, the height of the peaks, the
difference between the highest and the lowest pressure for each
peak, the average of these differences, etc. From these
measurements, a statistical analysis (factor analysis) identifies
the two most representative parameters: the surface area of the
peaks and the surface area of the plateaus.
In order to classify patients into groups to help the
physician in his diagnosis, signals from the pressure transducer
are recorded for a complete night during the patient's sleep.
The corresponding curve is plotted. As previously indicated, to
each tumescence period correspond a pressure plateau and one or
more pressure peaks, the surface areas of which may be
calculated. Results of these evaluations are then plotted on a
chart with the surface area of peaks on the X-axis and the
surface area of the plateau on the Y-axis. A curve with time on
the X-axis and pressure on the Y-axis is also plotted and
provides a representation of the pressure, the length of the
pressure plateau and the maximum pressure of the peaks.
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Four patient groups or clusters are identified:
1. weak: for whom the two surface areas
measured are relatively small; they do not
have tumescence,
2. average: with limited tumescence and
erection lacking in rigidity,
3. muscular pathology: with satisfactory
tumescence but little rigidity,
4. hyper: with satisfactory tumescence and
rigidity.
The fact that the photoplethysmography signal drops
when the ICP increases is a handicap that can be corrected by
software. Establishing the relation between ICP and changes in
the photoplethysmography signal is sufficient to obtain a
measurement of the real flow.
In order to prevent these problems, it is preferable to
have the photoplethysmography probe attached to a compressible
container filled with air, which is compressible. Such a device
(cuff 1 with a container 3 filled with air) also provides a means
to measure pressure. However, to measure pressure it is
preferable to use a non compressible fluid, such as water.
In an alternative embodiment of the apparatus
represented in Fig. 2, the cuff 1 is provided with two containers
31 and 32. The first container 31 is filled with water and is
used to measure pressure in the manner previously described for
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the apparatus of Fig. 1. The second container 32 is filled with
air which is kept at a constant pressure using a pressure
regulator 13. the photoplethysmography probe 10 is attached to
the second container 32 which is transparent. As in the first
embodiment, the light beam emitted by the photoplethysmography
probe diode may be directed toward the container 32 or toward the
skin of the appendage on which the cuff is positioned.
Measurements with this embodiment of the apparatus are
carried out using the same method as with the first embodiment.
the difference in this case being that the signal from the
photoplethysmograph is more sensitive and more accurate.
Additionally, the apparatus of this invention may be
combined with a penile circumference measuring means, such as a
mercury filled gauge 15 like the standard plethysmograph used to
measure increases in penile circumference. This combination
provides a means whereby the compliance of the corpus cavernosum
may be calculated as the result of the change in Volume divided
by the change in ICP. Thus, the ICP is measured using the
pressure cuff of the invention simultaneously with the
measurement of penile circumference from the mercury gauge. The
change in Volume is derived from the change in penile
circumference, and is then divided by the change in ICP as
measured by the pressure cuff to obtain a value for the
compliance of the corpus cavernosum. The mercury gauge, or
plethysmograph, may be provided as a separate cuff which is
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applied to the penis adjacent to the cuff 1 of the present
apparatus, or it may be incorporated into the cuff 1 as shown in
Fig. 3. In this embodiment, the mercury filled gauge 15 is
formed as a separate container 16 on the cuff 1. A signal
generator 17 senses the variation in electrical resistance and
provides a signal to the recording unit 14 or the computer 8
which is translated into a measure of the increase in penile
circumference.
Although described primarily in connection with the
measurement of tumescence and intra-cavernosal pressure of the
penis for diagnosis in cases of erectile dysfunction, the
apparatus of this invention is suitable for use in the
measurement of blood flow and pressure in other appendages of the
body, for example the hand or foot of stationary or ambulatory
patients. Using the apparatus of this invention and the same or
similar methods, one can measure, monitor and evaluate changes in
arterial and venous blood flow and tissue pressures in other
appendages over a period of time and particular activity.
The above embodiments and drawings illustrate the
preferred embodiments of the present invention and it is
understood that many variations and modifications of those
embodiments will be evident to those skilled in the art and may
be carried out without departing from the spirit and scope of the
present invention.
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