U.S. patent application number 12/130988 was filed with the patent office on 2008-11-06 for method and device for measurements in blood.
Invention is credited to Anna Dahlstrom, Hans Pettersson, Magnus Pettersson.
Application Number | 20080275320 12/130988 |
Document ID | / |
Family ID | 32684367 |
Filed Date | 2008-11-06 |
United States Patent
Application |
20080275320 |
Kind Code |
A1 |
Pettersson; Magnus ; et
al. |
November 6, 2008 |
METHOD AND DEVICE FOR MEASUREMENTS IN BLOOD
Abstract
We present an optical probe arrangement that surrounds blood in
a receptacle. It comprises LED's and light detector arranged to
overcome the variations when the receptacle is translucent medical
tubing and the like. Also, a signal processing algorithm is used to
average signals from a plurality of light detectors, to further
enhance results when measuring hematocrit. The invention makes it
possible to add the feature of hematocrit measurement into dialysis
system without major alterations to the dialysis machine or
transport tubing.
Inventors: |
Pettersson; Magnus;
(Linkoping, SE) ; Dahlstrom; Anna; (Linkoping,
SE) ; Pettersson; Hans; (Linghem, SE) |
Correspondence
Address: |
HAYES SOLOWAY P.C.
3450 E. SUNRISE DRIVE, SUITE 140
TUCSON
AZ
85718
US
|
Family ID: |
32684367 |
Appl. No.: |
12/130988 |
Filed: |
May 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10528091 |
Mar 16, 2005 |
7420658 |
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PCT/SE03/02013 |
Dec 18, 2003 |
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12130988 |
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Current U.S.
Class: |
600/322 ;
356/39 |
Current CPC
Class: |
G01N 2015/0065 20130101;
A61B 5/14535 20130101; G01N 21/53 20130101; G01N 15/0211 20130101;
G01N 21/05 20130101; A61B 5/14557 20130101 |
Class at
Publication: |
600/322 ;
356/39 |
International
Class: |
A61B 5/1455 20060101
A61B005/1455; G01N 33/49 20060101 G01N033/49 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2002 |
SE |
0203868-5 |
Dec 20, 2002 |
SE |
0203869-3 |
Claims
1-3. (canceled)
4. Sensor device for the measuring of the density of a fluid
flowing through a transparent tubing, said device comprising an
elongate frame sized to fit around the tubing, said frame carrying
a light beam emitter facing the tubing, and one or several
sensor(s) also facing the vessel and so arranged that its or their
sense sectors do not intersect the beam of the light source in the
vessel or tubing.
5. Sensor device according to claim 4, wherein the locations of the
light source and sensor(s) respectively are separated lengthwise of
the frame.
6. Sensor device according to claim 4, wherein two sensors are
arranged with their sensing directions perpendicular to the light
beam.
7. An optical probe arrangement that surrounds a fluid flowing
through an elongate transparent tubing, said optical probe
arrangement comprising a frame sized to surround said receptacle in
part, said frame supporting at least two sets of light emitters and
light detectors, each set comprising one light emitter and at least
one detector, each set arranged to transilluminate the fluid at a
preferred angle between said light emitter and said light
detector--or detectors--of each set, where said angle is at least
sufficient to avert direct light from said light emitter to said
light detector, for the detection of constituents in said
fluid.
8. An optical probe arrangement according to claim 7, comprising
four sets of light emitters and two or three light detectors in
each set, wherein a light detector represents a detector
incorporated in an adjacent set.
9. An optical probe arrangement according to claim 7, wherein the
light emitters are arranged as an array to encircle said elongated
tubing at longitudinally one location around said tubing's
circumference, and the light detectors are arranged to encircle the
tubing at a different circumferential location.
10. An optical probe arrangement according to claim 7, wherein a
second array of light detectors are longitudinally located at a
third location around said tubing's circumference, and the light
detectors are arranged to encircle the tubing at that
circumferential location.
11. A method for processing signals from sensor devices as claimed
in claim 4, including an amplifier for amplifying signals from the
sensor devices, which comprises applying a signal processing
algorithm on the signals from said sensor devices to calculate
density.
12. A method for processing signals from light detectors as claimed
in claim 11, which comprises applying a signal processing algorithm
on the signals from said light detectors, to detect said
constituents.
13. A method according to claim 12, which comprises applying a
multi variable analysis of signals from all light detectors engaged
in the signaling process.
14. A sensor device as claimed in claim 4, wherein a third array of
light sensors is longitudinally located at a fourth location around
said tubing's circumference, and the light sensors are arranged to
encircle the tubing at that circumferential location and an second
array of light beam emitters is longitudinally located at a fifth
location around said tubing's circumference, and the light sensors
are arranged to encircle the tubing at that circumferential
location.
15. A method for processing signals from light sensors as claimed
in claim 14, including an amplifier for amplifying signals from the
light sensors, which comprises applying a signal processing
algorithm on the signals from said light sensors, calculate
density.
16-17. (canceled)
18. A method according to claim 11, wherein signals are processed
in a time domain.
19. A sensor device according to claim 4, further comprising a
system to calculate density, and presenting the data to a display,
and/or transferring data to another application.
20. (canceled)
21. Method for the measuring of the density of a fluid flowing in a
tube, comprising directing of a light beam into the tube and that
two sensors, are used that are opposed to each other.
22. Method according to claim 21, characterized in that light beam
and sensor beam(s) are perpendicular to each other.
23. A sensor device as claimed in claim 4, characterized in that
the measuring takes place in a tubing that is clamped in a holder
with generally V-shaped recesses so that tube is given a
substantially square cross section and that light emitters and
sensors are arranged at the flat surfaces.
24. A method for processing signals from light detectors as claimed
in claim 7, including an amplifier for amplifying signals from the
light detectors, which comprises applying a signal processing
algorithm on the signals from said light detectors, to detect
constituents in the fluid.
25. A method according to claim 24, which comprises applying a
multi variable analysis of signals from all light detectors engaged
in the signaling process.
26. An optical probe arrangement as claimed in claim 7, wherein a
third array of light detectors is longitudinally located at a
fourth location around said tubing's circumference, and the light
detectors are arranged to encircle the tubing at that
circumferential location, and an second array of light emitters
longitudinally is located at a fifth location around said tubing's
circumference, and the light detectors are arranged to encircle the
tubing at that circumferential location.
27. A method for processing signals from light detectors as claimed
in claim 26, including an amplifier for amplifying signals from the
light detectors, and which comprises applying a signal processing
algorithm on the signals from said light detectors, to detect said
constituents.
28. A method according to claim 15, wherein signals are processed
in a time domain.
29. A method according to claim 24, wherein signals are processed
in a time domain.
30. A method according to claim 27, wherein signals are processed
in a time domain.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 10/528,091, filed Mar. 16, 2005.
BACKGROUND OF THE INVENTION
[0002] Hematocrit is the concentration of red blood cells (RBC) in
blood. The measurement of hematocrit values is of great importance
in the assessment of the condition of a patient. The established
method of measuring hematocrit is by drawing blood from the subject
(patient). Various methods to optically measure hematocrit by
optical or ultrasonic means have been attempted, e.g., during a
dialysis treatment of a patient. In these situations, not only the
level of hematocrit is of high importance but also the relative
variation of this parameter. In order to provide an optimized but
still safe dialysis treatment the change of the hematocrit or
relative blood volume has to be monitored during the treatment. The
attempts to monitor this have so far not resulted in any product
that can measure the hematocrit without a special cuvette
integrated in the transport tubing. The methods used so far have
therefore increased the cost of every dialysis treatments since the
transport tubing must be equipped with this single-use cuvette. The
invention presented here does not require any special cuvette,
instead it provides the possibility to measure the hematocrit, or
monitor the change of relative blood volume directly on any
standard dialysis transport tubing on the market without increasing
the cost of each treatment.
TECHNICAL FIELD
[0003] The invention relates to measuring various blood
constituents with optical means. Blood is irradiated
with--preferably--near infrared or infrared light. Light scattering
and attenuation of the light is measured and novel compensations
for optical variations in the receptacle walls, flow etc. is used
to calculate blood constituents such as hematocrit. The invention
makes it possible to add the feature of hematocrit measurement
without major alterations into any dialysis system. The addition of
this feature makes blood volume measurements at hand.
PRIOR ART
[0004] Hematocrit has been measured with various methods since the
beginnings of medical diagnosis. Continuous measurement is
particularly useful during dialysis treatment. During the process
of dialysis, liquids are extracted from the blood stream. As a
result, hematocrit increases during the process. For the assurance
of good quality in the dialysis treatment, the hematocrit value
should be monitored, as this provides the care provider with
essential information regarding the rate of extraction of fluids
from the patient's bloodstream.
[0005] Various techniques have been presented in the field of
optical measurements of hematocrit in blood. Several make use of
the scattering effect RBC has on light passing trough blood in a
vessel, cuvette or the like. Oppenheimer presents in U.S. Pat. No.
5,601,080 a method to measure the degree of scatter to derive blood
constituents.
[0006] Other patents are U.S. Pat. No. 4,745,279 to Karkar,
describing scattering effect of blood in a cuvette. U.S. Pat. No.
6,493,567 to Krivitski et al. describes a measuring instrument
using one light emitting diode and one sensor. U.S. Pat. No.
6,064,474 to Wylie et al is another description of a hematocrit
measuring method using the scattering effect RBC has on light.
However the known methods and devices do not provide a satisfactory
precision.
THE INVENTION
[0007] The above objects are in accordance with the invention
achieved by emitting light into the blood and then two detectors
placed opposite each other are used to execute the measuring.
[0008] In accordance with the present invention, a new method and a
novel apparatus are presented to measure blood properties with a
procedure comprising a new optical probe arrangement that overcomes
the problem of the prior art, as for instance optical variations,
such as optical density, refractions etc. The invention may even
take the shape of a clamp that with great ease can be applied on a
transparent tubing such as transport tubing in dialysis. The new
probe makes hematocrit values available with unsurpassed precision
in the art, in spite of the fact that it measures through
transparent tubing that vary in thickness and shape.
[0009] In the practical embodiment of the invention the blood is
measured as it flows through a transparent tubing. A beam of light,
for instance from a laser is directed perpendicular into the tube
and two sensors opposed to each other and perpendicular to the
light beam pick up light and the sensor signals are used for the
evaluation. The light source and the sensors may lie in the same
plane but the plane of the sensors may also be slightly offset in
relation to the light beam, for instance along the tubing. One can
also consider using several pairs of sensors offset along the
tubing and upstream as well as downstream in order to increase
precision. Also a third sensor may be added to each pair, this
third sensor being placed close to the light source.
[0010] In this solution the sensor offset in relation to the light
source may advantageously be so large that the sensing sectors of
the two sensors do not intersect the light beam. With increasing
offset the sensitivity to relative changes is increased, whereas a
smaller offset will provide a more accurate absolute measurement of
the hematocrit value. It is thus possible to use one set of sensors
to establish an absolute value and then use a set of more offset
placed sensors for the monitoring and controlling of the level
during dialysis.
[0011] Further preferable developments are apparent from the claims
and the following description of a preferred embodiment of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross section of an optical probe arrangement 1,
accommodating light emitting diodes 5 in holes 4 in a framework
comprising two halves 2 and 3 suited to fit a receptacle 8 such as
tubing for blood 9.
[0013] FIG. 2 is a cross section of an optical probe arrangement 1,
accommodating light detectors 6 in holes 4 in a framework
comprising two halves 2 and 3 suited to fit a receptacle 8 such as
tubing for blood 9.
[0014] FIG. 3 depicts the arrangement of the array of light
detectors 5 and light emitting diodes 6 on the optical probe
arrangement 1. This is a suggestion where the arrays according to
FIG. 1 and FIG. 2 are located with indication "A-A" for the light
emitting diodes, and "B-B" for the light detectors.
[0015] FIG. 4 depicts the arrangement of a second array of light
detectors 7.
[0016] FIG. 5 depicts the optical probe arrangement 1 with the
farther embodiment of light emitting diodes 9, and photo detectors
8.
[0017] FIG. 6 depicts the resulting hematocrit values with
reference to measurements performed at an accredited clinical
laboratory.
DESCRIPTION
[0018] We have achieved very good results by using the following
arrangement of light-emitting diodes (LED's) and photo detectors,
when assessing hematocrit values. These values correlate very well
with laboratory reference values.
[0019] Four LED's are arranged in a preferably--but not limited
to--perpendicular fashion to each other around a receptacle, such
as tubing, for the blood as apparent in FIG. 1. The light detectors
are arranged in a fashion where they similarly are preferably
perpendicular to each other according to FIG. 2, but at a distance
longitudinally away from the encirclement by the LED's, as
exhibited in FIG. 3. In a further embodiment, a second encirclement
of light detectors is fitted. The arrangement is apparent in FIG.
4.
[0020] The LED and photo detector arrangement should for best
understanding be viewed as groups of LED's and photo detectors: For
instance, LED 5 a, and photo detector 6 b is one group. Another
group can be LED 5 b, and photo detector 6 a and 6 c. Note that no
LED's and photo detectors are aligned to achieve direct transmitted
light. The invention does not make use of directly transmitted
light, as often is the case in prior art.
[0021] A sample of light detected from a group of one or several
photo detectors can be taken at any one short instance in time.
Another sample can be taken from the same or another group as a
second sample. Preferably, a first sample is taken from a first
group comprising LED 5 a, and light detectors 6 b and 6 d, a second
sample is taken from a second group comprising LED 5 b, and light
detectors 6 a and 6 c, a third sample is taken from a third group
comprising LED 5 c, and light detectors 6 b and 6 d, and finally a
forth sample is taken from a fourth group comprising LED 5 d, and
light detectors 6 a and 6 c. A first result is derived from theses
four sequentially acquired samples being signal processed. The
process can include variations of amplification factors for the
signals from the detectors, and also correlation factors between
these signals, to further enhance the detection of the blood
constituent to be measured. The results make a first result for
blood constituents, such as hematocrit. In this process, the error
occurring from variations in the cross section of the flow pattern
in the vessel is reduced. Furthermore averaging may reduce the
effect the vessel wall has on the measurement. This is highly
beneficial if the vessel is the extracorporal circuit of a dialysis
system. One of the major advancements in the disclosed invention
resides in the new possibility to measure hematocrit trough the
walls of dialysis extracorporal circuit, namely the so-called
transport tubing of the circuit. It is highly advantageous that no
special cuvettes or dedicated arrangements to the disposable
bloodlines are necessary. Our process even makes it unnecessary to
fit dedicated tubing to the extracorporeal circuit. This feature is
considerably cost saving for the health care provider. Fitting the
hereby disclosed probe on the transport tubing also has the
advantage that the probe is not interfering with the ordinary
functions of the dialysis system. Also, it furnishes the highly
beneficial possibility to upgrade any already existing dialysis
system with measurement of hematocrit, even if it is not prepared
for such purpose. Subsequently blood volume changes can be
calculated and displayed.
[0022] In one embodiment of the invention, two arrays of detectors
are employed. Downstream (or upstream) a blood flow in a vessel
such as tubing, a second array of detectors is fitted. This is
apparent in FIG. 4. The mathematical signal processing can further
enhance the results by including this "second order" of detectors
in the process.
[0023] In another embodiment of the invention, a second arrangement
of LED's and photo detectors, including a second array of detectors
is fitted. This is exhibited in FIG. 5. In this embodiment, the
LED's emits a different wavelength. This allows limited spectral
analysis for further calculation of blood constituents, such as
saturation of hemoglobin as known in the art. The results derived
from this second array, can beneficially be incorporated in a
signaling process with the values derived from the aforementioned
first array. Such process makes it possible not only to output all
parameters from blood constituents, but also let the saturation
value influence the input of signals from the first array to the
signaling process. This is beneficial, as blood saturation may
influence the first results of blood constituents from the first
process from the first array.
[0024] In the drawings and the above description a transparent
blood transporting tubing is shown clamped between two essentially
V-shaped profiles in the walls of which the led and sensors are
arranged. In an alternative embodiment V-shaped groves in blocks
may be used to clamp and shape the tubing so that its walls become
essentially flat at LEDs and sensors.
[0025] In a further embodiment the sensors may be arranged in small
holes with even smaller openings serving as collimators towards the
tubing.
[0026] It is not today clear why the invented measuring method and
device are so superior in relation to the prior art, one theory
could be the offset between sensors and light source. Only light
that has been dispersed from the volume of the blood in the path of
the light and into the sense sector of the sensor and from this
into the sensor will be registered. In other words only light that
has been dispersed at least twice will reach the sensor. By
arranging source and sensor perpendicularly blood cells in a major
part of the tube cross section will have the opportunity to
contribute so that the signals from the sensors become a function
of the hematocrite value.
* * * * *