U.S. patent application number 09/725865 was filed with the patent office on 2001-11-22 for apparatus for determining concentrations of hemoglobins.
Invention is credited to Kanemoto, Michio, Kobayashi, Naoki, Ukawa, Teiji, Usuda, Takashi.
Application Number | 20010044700 09/725865 |
Document ID | / |
Family ID | 26576468 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010044700 |
Kind Code |
A1 |
Kobayashi, Naoki ; et
al. |
November 22, 2001 |
Apparatus for determining concentrations of hemoglobins
Abstract
An apparatus for determining concentrations of hemoglobins
additionally uses a light source 3 which emits light of a third
wavelength in an orangy red wavelength region of 590 to 660 nm. The
apparatus includes light receiving means 6 for receiving lights
that are emitted by the light sources and transmitted through or
reflected by a living tissue, attenuation ratio processing means 15
for processing attenuation ratios .PHI. on the wavelengths based on
variations of signals associated with the wavelengths output from
the light receiving means, which variations are caused by a
pulsation of blood, and concentration ratio processing means 16 for
processing concentration ratios of at least oxyhemoglobin,
deoxyhemoglobin and carboxyhemoglobin based on the output signals
from the attenuation ratio processing means. The apparatus thus
constructed can properly measure carboxyhemoglobin COHb, and
present its concentration display and an alarm display in a simple
manner, which is clinically effective.
Inventors: |
Kobayashi, Naoki; (Tokyo,
JP) ; Kanemoto, Michio; (Tokyo, JP) ; Usuda,
Takashi; (Tokyo, JP) ; Ukawa, Teiji; (Tokyo,
JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
2100 Pennsylvania Avenue N.W.
Washington
DC
20037
US
|
Family ID: |
26576468 |
Appl. No.: |
09/725865 |
Filed: |
November 30, 2000 |
Current U.S.
Class: |
702/31 |
Current CPC
Class: |
A61B 5/14551 20130101;
A61B 5/0059 20130101 |
Class at
Publication: |
702/31 |
International
Class: |
G06F 019/00; G01N
031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 1999 |
JP |
P. HEI. 11-339605 |
Sep 21, 2000 |
JP |
P. 2000-286927 |
Claims
What is claimed is:
1. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of at least three
different wavelengths, a first wavelength in a near-infrared
wavelength region of 790 to 100nm, a second wavelength in a red
wavelength region of 640 to 675 nm, and a third wavelength in an
orangy red wavelength region of 590 to 660 nm; light receiving
means for receiving light emitted by said light source, transmitted
through a living tissue or reflected by the living tissue;
attenuation ratio processing means for processing attenuation
ratios on said wavelengths based on variations of signals
associated with said wavelengths output from said light receiving
means, said variations are caused by a pulsation of blood; and
concentration ratio processing means for processing concentration
ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means.
2. An apparatus for determining concentrations of hemoglobins
according to claim 1, wherein said concentration ratio processing
means processes concentration ratios of oxyhemoglobin,
deoxyhemoglobin and carboxyhemoglobin on the assumption that an
optimized linear relation is present between the concentrations of
said hemoglobins and the attenuation ratios .PHI. output from said
attenuation ratio processing means.
3. An apparatus for determining concentrations of hemoglobins
comprising; a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light sourcer transmitted through a living tissue or reflected
by the living tissue; attenuation ratio processing means for
processing attenuation ratios on said wavelengths based on
variations of signals associated with said wavelengths output from
said light receiving means, said variations caused by a pulsation
of blood; concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means; and oxygen saturation processing means for
processing one of a functional oxygen saturation and a fractional
arterial oxygen saturation based on an output signals of said
concentration ratio processing means.
4. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light source , transmitted through a living tissue or
reflected by a living tissue; attenuation ratio processing means
for processing attenuation ratios on said wavelengths based on
variations of signals associated with said wavelengths output from
said light receiving means, said variations caused by a pulsation
of blood; concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means; and alarm display means for displaying an
alarm in accordance with a level of a concentration ratio of
carboxyhemoglobin produced from said concentration ratio processing
means.
5. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light source, transmitted through a living tissue or reflected
by the living tissue; attenuation ratio processing means for
processing attenuation ratios on said wavelengths based on
variations of signals associated with said wavelengths output from
said light receiving means, said variations caused by a pulsation
of blood; concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means; event input means for inputting events on
the medical treatment on a patient when said events occur; and
storing means for storing times and event information as input by
said event input means, and the processing results output from said
concentration ratio processing means.
6. An apparatus for determining concentrations of hemoglobins
according to claim 5, further comprising: display means for
displaying trends of said processing results, and said event
information that is stored in said storing means.
7. An apparatus for determining concentrations of hemoglobins
according to claim 5, further comprising: an interface used for
transmitting said event information, said times and said processing
results, which are stored in said storing means, to an external
device.
8. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light source, transmitted through the living tissue or
reflected by the living tissue; value input means for inputting a
concentration value of at least one kind of light absorbing
material in blood for calibration; attenuation ratio processing
means for processing attenuation ratios on said wavelengths based
on variations of signals associated with said wavelengths output
from said light receiving means, the variations caused by a
pulsation of blood; and concentration processing means for
processing concentrations of at least oxyhemoglobin,
deoxyhemoglobin and carboxyhemoglobin based on the output signals
from said attenuation ratio processing means and said concentration
value of said in-blood material input by said value input
means.
9. An apparatus for determining concentrations of hemoglobins
according to claim 8, further comprising: storing means for storing
data on attenuation ratio, wherein said concentration processing
means retrospectively processes over again at least one of
oxyhemoglobin, deoxyhemoglobin and carboxyhemoglobin by using said
data stored in said storing means and said in-blood material
concentration value input to said value input means.
10. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light source , transmitted through or reflected by a living
tissue; attenuation ratio processing means for processing
attenuation ratios on said wavelengths based on variations of
signals associated with said wavelengths output from said light
receiving means, which variations are caused by a pulsation of
blood; concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means; and select means for giving an instruction
to process a concentration ratio of carboxyhemoglobin; wherein when
said select means does not give an instruction to process a
concentration ratio of carboxyhemoglobin, said concentration ratio
processing means processes concentration ratios of oxyhemoglobin
and deboxyhemoglobin on the basis of variations of signals output
from said light receiving means upon reception of lights of at
least two different wavelengths that are emitted from said light
source and transmitted through and reflected by a living tissue,
and when said select means gives an instruction to process a
concentration ratio of carboxyhemoglobin, said concentration ratio
processing means processes concentration ratios of oxyhemoglobin,
deoxyhemoglobin and carboxyhemoglobin on the basis of variations of
signals output from said light receiving means upon reception of
lights of at least three different wavelengths that are emitted
from said light source and transmitted through and reflected by a
living tissue.
11. An apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving light emitted by
said light source, transmitted through a living tissue or reflected
by the living tissue; attenuation ratio processing means for
processing attenuation ratios on said wavelengths based on
variations of signals associated with said wavelengths output from
said light receiving means, said variations caused by a pulsation
of blood; concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from said attenuation
ratio processing means; and display means for displaying measured
values of oxyhemoglobin, deoxyhemoglobin and carboxyhemoglobin on
the X-Y coordinates.
12. An apparatus for determining concentrations of hemoglobins
according to claim 3 , wherein said light source for emitting
lights of at least three different wavelengths, a first wavelength
in a near-infrared wavelength region of 790 to 1000nm, a second
wavelength in a red wavelength region of 640 to .sup.675 nm, and a
third wavelength in an orangy red wavelength region of 590 to 660
nm.
13. An apparatus for determining concentrations of hemoglobins
according to claim 4, wherein said light source for emitting lights
of at least three different wavelengths, a first wavelength in a
near-infrared wavelength region of 790 to 1000nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
14. An apparatus for determining concentrations of hemoglobins
according to claim 5, wherein said light source for emitting lights
of at least three different wavelengths, a first wavelength in a
near-infrared wavelength region of 790 to 1000 nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
15. An apparatus for determining concentrations of hemoglobins
according to claim 8, wherein said light source for emitting lights
of at least three different wavelengths, a first wavelength in a
near-infrared wavelength region of 790 to 1000 nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
16. An apparatus for determining concentrations of hemoglobins
according to claim 10, wherein said light source for emitting
lights of at least three different wavelengths, a first wavelength
in a near-infrared wavelength region of 790 to 1000 nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
17. An apparatus for determining concentrations of hemoglobins
according to claim 11, wherein said light source for emitting
lights of at least three different wavelengths, a first wavelength
in a near-infrared wavelength region of 790 to 1000nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the measurements of oxygen
saturations and concentrations of hemoglobins in arterial blood by
using a pulse oximeter, and more particularly to the measurement of
a concentration of carboxyhemoglobin.
[0003] 2. Related art
[0004] A conventional pulse oximeter is constructed such that
near-infrared rays of light and red rays of light are irradiated
onto a living tissue, ratios of the pulsating components of
attenuations of these lights having passed through the living
tissue are processed, and an arterial oxygen saturation is
noninvasively measured from the result of the computation.
[0005] The measuring principle of the pulse oximeter is known as
disclosed in JP-A-53-26437, proposed by the applicant of the
present patent application. The measuring principle of the pulse
oximeter will be described in brief hereunder.
[0006] AS shown in FIGS. 9(A) and 9(B), a living tissue R is
divided into a blood layer R1 and a layer R2 of a tissue from which
blood has removed (this tissue will be referred to as a pure
tissue), and it is assumed that a thickness of the blood layer R1
is pulsated, but a thickness of the pure tissue layer R2 is not
pulsated, viz., it is constant, where the living tissue R is
irradiated with light, an incident light amount IO is reduced by
the living tissue R, and an amount of light passing through the
living tissue R is I. When a thickness of the blood layer R1 is
pulsated to be increased by .DELTA.Db, the amount of the
transmitted light is reduced to be (I-.DELTA.I). In this case, an
attenuation .DELTA.A of the light, which is produced by a thickness
change .DELTA.Db of the blood layer R1, is given by
.DELTA.A=log [I/(I-.DELTA.I)]
[0007] When lights of different wavelengths .lambda.1 and .lambda.2
are irradiated onto the living tissue R, a ratio .PHI. of
attenuations .DELTA.A1 and .DELTA.A2 of lights of the wavelengths
.lambda.1 and .lambda.2, which are produced by the pulsation of the
tissue thickness is mathematically approximated by
[0008] [Expression 1]
.PHI.=.DELTA.A1/.DELTA.A2=[{square root}{square root over
(])}(E1(E1+F)}]/[{square root}{square root over ( )}{E2(E2+F)}]
(1)
[0009] This is theoretically and empirically confirmed.
[0010] In the above expression, E1,2(Ei) are absorption
coefficients, F is a scattering coefficient of light in blood and
has no wavelength dependency, and suffixes 2 represent the
wavelengths .lambda.1 and .lambda.2. Assuming that light absorbing
materials in blood are only oxyhemoglobin and deoxyhemoglobin, then
the absorption coefficient Ei of the hemoglobin is given by the
following expression.
Ei=SEOi+(1-S)Eri (2)
[0011] In the expression, S is an oxygen saturation, and Eoi and
Eri are an absorption coefficient Eoi of oxyhemoglobin and
absorption coefficient Eri of deoxyhemoglobin. Substituting the
expression (2) for the expression (1), then we have the following
expression
[0012] [Expression 3] 1 = A1 / A2 = [ { [ SEo1 + ( 1 - S ) Er1 ) {
SEo1 + ( 1 - S ) Er1 + F ) } ] / [ { ( SEo2 + ( 1 - S ) Er2 ) (
SEo2 + ( 1 - S ) Er2 + F ) } ] ( 3 )
[0013] In the expression (3), Eo1, Er1, Eo2, Er2 and F are known
values. Therefore, an oxygen saturation S can be obtained in a
manner that .PHI.=.DELTA.A1/.DELTA.A.sub.2 is measured, substituted
for the expression (3), and the expression is solved for the S.
[0014] The conventional pulse oximeter using two wavelengths of
near-infrared rays of light and red rays of light cannot detect an
increase of a concentration of carboxyhemoglobin COHb in blood.
Accordingly, it has a disadvantage that an arterial oxygen
saturation displayed is higher than an actual one. When the pulse
oximeter is coupled to a patient suffering from carbon monoxide
poisoning and operated for the monitoring, the result of the
measurement by the pulse oximeter will lead to such
misunderstanding by the medical staff that the sufficient amount of
oxygen is present even though an amount of transporting oxygen is
actually reduced. This is tremendously dangerous for the patient.
In diagnosing a patient showing the carbon monoxide poisoning, it
is very difficult to judge the illness as the carbon monoxide
poisoning from only the symptoms of the patient. Accordingly, the
carbon monoxide poisoning has frequently been missed in the
diagnosis of the patient, though it is dangerous.
[0015] It is reported that in the operation under anesthesia, a
patient shows the carbon monoxide poisoning in which a
concentration of the carbon monoxide in blood reaches 10 to 30%.
The cause of it is estimated that inhalative anesthetic and dried
CO2 absorbent generate carbon monoxide. However, the conventional
pulse oximeter cannot find the generated carbon monoxide.
Accordingly, there is a danger of missing the generation of the
carboxyhemogrobin.
[0016] Meanwhile, where the arterial blood pulsates, the theory
teaches that concentration ratios of "n" number of light absorbing
materials in the blood can be measured by using "n" number of
wavelengths of lights. Accordingly, the theory also teaches that it
is impossible to measure concentration ratios of three hemoglobins,
oxyhemoglobin O2Hb, deoxyheoglobin RHband carboxyhemoglobin COHb by
using two wavelengths of lights, and at least three wavelengths
must be used for the measurement.
[0017] Actually, however, the influence by puretissues other than
the blood will produce measuring errors. Accordingly, to accurately
measure concentrations of "n" number of light absorbing materials
in the blood, it is preferable to use (n+1) number of wavelengths.
This fact was found and confirmed by us. The applicant of the
present patent application developed an apparatus for determining
concentrations of materials in blood based on the above fact, and
filed the patent application on the apparatus (JP-B-5-88609). Other
light absorbing materials, such as methemoglobin and bilirubin, are
also contained in the blood. To remove the influence by those
materials is attempted, the number of wavelengths used is further
increased, and further cost to manufacture the apparatus is also
increased.
[0018] In adding a third wavelength for measuring the
carboxyhemoglobin COHb to the pulse oximeter (JP-A-5-228129), the
absorption coefficients of it at the wavelengths of lights, which
are longer than the red wavelengths, as shown in FIG. 10, are
extremely small. Accordingly, it is very difficult to detect it.
The absorption coefficient of the carboxyhemoglobin COHb at the
wavelength of 700 nm is about {fraction (1/10)} as large as that of
oxyhemoglobin O2Hb. Accordingly, in this case, a change of the
transmitted light which results from a change of the
carboxyhemoglobin COHb, is about {fraction (1/10)} as large as a
change of the same which results from a change of the oxyhemoglobin
O2Hb, and is extremely small. For this reason, where the third
wavelength is selected from those wavelengths ranging from the red
wavelengths to near-infrared wavelengths, a sensitivity of the
apparatus is too small to discriminate the carboxyhemoglobin COHb
from other hemoglobins Hb., and it is very difficult to measure the
carboxyhemoglobin COHb. Scharf proposed in his patent (U.S. Pat.
No. 5,830,137) the use of the green wavelength region for the third
wavelength. The absorption coefficient of every kind of hemoglobin,
as shown in FIG. 10, is considerably large in the yellow and green
wavelength regions. The absorption coefficients of the
carboxyhemoglobin COHb and the oxyhemoglobin O2Hb in the wavelength
region of 500 nm to 590 nm are at least 10 times as large as those
at 660 nm. Light having passed through the blood is very weak, and
the measurement at good S/N ratio is very difficult.
SUMMARY OF INVENTION
[0019] Accordingly, an object of the present invention is to
provide an apparatus for determining concentrations of hemoglobins
which, using an orange or orangey red wavelength region for the
third wavelength in addition to the near-infrared and red
wavelengths, which are conventionally used, can detect a change of
the transmitted light by a change of the carboxyhemoglobin COHb at
good S/N ratio, and can easily discriminate between the
carboxyhemoglobin COHb and the deoxyhemoglobin RHb, and hence can
perform a proper measurement of carboxyhemoglobin COHb.
[0020] Another object of the invention is to provide an apparatus
for determining concentrations of hemoglobins, which includes a
hemoglobin concentration indication system capable of indicating
carboxyhemoglobin COHb concentrations measured by the apparatus as
referred to in the major object, in a clinically effective, simple
manner.
[0021] To achieve the above object, there is provided an apparatus
for determining concentrations of hemoglobins comprising: a light
source for emitting lights of at least three different wavelengths,
a first wavelength in a near-infrared wavelength region of 790 to
1000 nm, a second wavelength in a red wavelength region of 640 to
675 nm, and a third wavelength in an orangy red wavelength region
of 590 to 660 nm;
[0022] light receiving means for receiving lights that are emitted
by the light source and transmitted through or reflected by a
living tissue;
[0023] attenuation ratio processing means for processing
attenuation ratios .PHI. on the wavelengths based on variations of
signals associated with the wavelengths output from the light
receiving means, which variations are caused by a pulsation of
blood; and
[0024] concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from the attenuation
ratio processing means.
[0025] In the apparatus for determining concentrations of
hemoglobins, the concentration ratio processing means processes
concentration ratios of oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin on the assumption that an optimized linear
relation is present between the concentrations of the hemoglobins
and the attenuation ratios .PHI. output from the attenuation ratio
processing means.
[0026] The apparatus further comprises oxygen saturation processing
means for processing a functional oxygen saturation or a fractional
arterial oxygen saturation based on an output signals of the
concentration ratio processing means.
[0027] The apparatus further comprises alarm display means for
displaying an alarm in accordance with a level of a concentration
ratio of carboxyhemoglobin determined by the concentration ratio
processing means.
[0028] The apparatus further comprises event input means for
inputting events on the medical treatment on a patient when the
events occur, and storing means for storing times and event
information as input by the event input means, and the processing
results output from the concentration ratio processing means.
[0029] The apparatus further comprises display means for displaying
trends of the processing results, and the event information that is
stored in the storing means .
[0030] The apparatus further comprises an interface used for
transmitting the event information, the times and the processing
results, which are stored in the storing means, to an external
device. According to another aspect of the invention, there is
provided an apparatus for determining concentrations of hemoglobins
comprising: a light source for emitting lights of different
wavelengths; light receiving means for receiving lights that are
emitted by the light source , transmitted through or reflected by a
living tissue; value input means for inputting a concentration
value of at least one kind of light absorbing material in blood for
calibration; attenuation ratio processing means for processing
attenuation ratios .PHI. on the wavelengths based on variations of
signals associated with the wavelengths output from the light
receiving means, which variations are caused by a pulsation of
blood; and concentration processing means for processing
concentrations of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from the attenuation
ratio processing means and the concentration value of the in-blood
material input by the value input means.
[0031] The apparatus further comprises storing means for storing
data on attenuation ratio .PHI., and wherein the concentration
processing means retrospectively processes over again at least one
of oxyhemoglobin, deoxyhemoglobin and carboxyhemoglobin by using
the data stored in the storing means and the in-blood material
concentration value input to the value input means.
[0032] The apparatus for determining concentrations of hemoglobins
comprises select means for giving an instruction to process a
concentration ratio of carboxyhemoglobin.
[0033] When the select means does not give an instruction to
process a concentration ratio of carboxyhemoglobin, the
concentration ratio processing means processes concentration ratios
of oxyhemoglobin and deoxyhemoglobin on the basis of variations of
signals output from the light receiving means upon reception of
lights of at least two different wavelengths that are emitted from
the light source and transmitted through and reflected by a living
tissue.
[0034] When the select means gives an instruction to process a
concentration ratio of carboxyhemoglobin, the concentration ratio
processing means processes concentration ratios of oxyhemoglobin ,
deoxyhemoglobin and carboxyhemoglobin on the basis of variations of
signals output from the light receiving means upon reception of
lights of at least three different wavelengths that are emitted
from the light source, transmitted through or reflected by a living
tissue.
[0035] According to yet another aspect of the invention, there is
provided an apparatus for determining concentrations of hemoglobins
comprising:
[0036] a light source for emitting lights of different
wavelengths;
[0037] light receiving means for receiving lights that are emitted
by the light source, transmitted through or reflected by a living
tissue;
[0038] attenuation ratio processing means for processing
attenuation ratios .PHI. on the wavelengths based on variations of
signals associated with the wavelengths output from the light
receiving means, which variations are caused by a pulsation of
blood;
[0039] concentration ratio processing means for processing
concentration ratios of at least oxyhemoglobin, deoxyhemoglobin and
carboxyhemoglobin based on the output signals from the attenuation
ratio processing means; and
[0040] display means for displaying measured values of
oxyhemoglobin, deoxyhemoglobin and carboxyhemoglobin on the X-Y
coordinates.
[0041] In the apparatus, the light source for emitting lights of at
least three different wavelengths, a first wavelength in a
near-infrared wavelength region of 790 to 1000 nm, a second
wavelength in a red wavelength region of 640 to 675 nm, and a third
wavelength in an orangy red wavelength region of 590 to 660 nm.
BRIEF DESCRIPTION OF DRAWINGS
[0042] FIG. 1 is a block diagram showing a system arrangement of an
apparatus for determining concentrations of hemoglobins, which is
an embodiment of the present invention.
[0043] FIG. 2 is a diagram showing a display arrangement of a
hemoglobin Hb concentration display unit in the FIG. 1
apparatus.
[0044] FIG. 3 is a diagram showing another display arrangement of
the hemoglobin Hb concentration display unit in the FIG. 1
apparatus.
[0045] FIG. 4 is a diagram showing still another display
arrangement of the hemoglobin Hb concentration display unit in the
FIG. 1 apparatus.
[0046] FIGS. 5(A) and 5(B) are diagrams showing additional display
arrangements of the hemoglobin Hb concentration display unit in the
FIG. 1 apparatus.
[0047] FIGS. 6(A) and 6(B) are diagrams showing different displays
by a trend display unit shown in FIG. 1.
[0048] FIG. 7 is a graph showing characteristic curves describing
relationships between two attenuation ratios .PHI.12 and .PHI.13 at
the wavelengths of lights applied to the hemoglobin concentration
determining apparatus.
[0049] FIG. a is a graph showing characteristic curves describing
relationships between two attenuation ratios .PHI.12 and .PHI.13 in
the hemoglobin concentration determining apparatus when a third
infrared wavelength of 805 nm is additionally used.
[0050] FIGS. 9(A) and 9(B) are cross sectional views showing a
pulsation of a pure tissue layer, which pulsates with a blood
layer.
[0051] FIG. 10 is a graph showing a relationship between absorption
coefficient and wavelengths, which are applied to the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0052] Principle of the invention
[0053] The inventors of the present patent application discovered
the following fact: when any of the orange or orangey red
wavelengths is used for the third wavelength, in addition to the
near-infrared and red wavelengths, which are conventionally used, a
change of the transmitted light which results from a change of the
carboxyhemoglobin COHb is detected at good S/N ratio, it is easy to
discriminate between the carboxyhemoglobin COHb and the
deoxyhemoglobin RHb, and hence it is possible to properly measure
the carboxyhemoglobin COHb.
[0054] Where the near-infrared wavelength is 940 nm, the red
wavelength is 660 nm, the near-infrared wavelength is 805 nm, and
the orange wavelength is 621 nm, the values of the concentration
ratios of deoxyhemoglobin RHb and carboxyhemoglobin COHb .PHI.12
and .PHI.32 were investigated. From the investigation, it was seen
that at the infrared wavelength of 805 nm, the directions in which
.PHI.12 and .PHI.32 change are coincident with each other for the
changes of both the deoxyhemoglobin RHb and the carboxyhemoglobin
COHb. In this state, it was found that it was difficult to
discriminate between the deoxyhemoglobin RHb and the
carboxyhemoglobin COHb as shown in FIG. 8. In the case of the
orange wavelength of 621 nm, the orthogonality of a changing
direction of the deoxyhemoglobin RHb and a changing direction of
the carboxyhemoglobin COHb, increases. Accordingly, the
discrimination is easy as shown in FIG. 7. This fact was found and
confirmed.
[0055] COHb concentrations are conventionally expressed every 10%
about acute carbon monoxide poisoning states (clinical symptoms) as
in the following table (1).
1TABLE 1 COHb concentration (%) Clinical symptoms less than 10% No
obvious symptoms 10-20 frontal pain, headache, vasodilation of the
skin 20-30 headache (pulsating), lack of vigor, emotional
disturbance 30-40 splitting, confusion, vomiting, lack of strength,
visual disorder 40-50 serious ataxia, hallucination, lack of
strength, muscle weakness, hyperventilation, tachycardia 50-60
coma, convulsion, Cheyne-Stokes respiration, death sometimes 60-70
deep coma, weak breathing more than 70% respiratory standstill,
circulatory collapse, death
[0056] As seen from Table 1, the correspondence between the
carboxyhemoglobin COHb concentration and the clinical symptoms will
suffice for the clinical purposes, while not depending on precise
expression of the COHb concentration (%) in steps of 1%. In an
example of the concentration expression, acute carbon monoxide
poisoning states may be expressed in two levels, "YES" and "NO",
with the CORb concentration of 20% as a critical value, in another
example of it, it may be expressed in three levels, "low
concentration", "medium concentration" and "high
concentration".
[0057] The preferred embodiment of an apparatus for determining
concentrations of hemoglobins, which is constructed according to
the present invention, will be described with reference to the
accompanying drawings.
[0058] Embodiments
[0059] FIG. 1 is a block diagram showing a system arrangement of an
apparatus for determining concentrations of hemoglobins constructed
to the present invention. In FIG. 1, reference numerals 1, 2 and 3
indicate light emitting elements as light sources. Those elements
1, 2 and 3, respectively, emit near-infrared light of a first
wavelength .lambda.1, which is any of 790 nmto 100nm, preferably
940 nm.+-.5 nm, red light of a second wavelength .lambda.2, which
is any of 640 nm to 675 nm, preferably 660 nm.+-.5 nm, and orangy
red light of a third wavelength .lambda.3, which is any of 590 nm
to 660 nm, preferably 621 nm.+-.5 nm. Those light emitting elements
are driven by a drive circuit 4. The lights emitted from those
elements 1, 2 and 3 transmit through a living tissue 5, and is
received by a light receiving element 6 as light receiving means.
The light receiving element 6 converts the lights into
corresponding electrical signals. Those electrical signals are
amplified by an amplifier 7, and applied to a multiplexer 8. The
multiplexer then delivers respectively those signals to filters 9,
10 and 11, which are provided corresponding to the wavelengths of
the lights.
[0060] Those filters 9 to 11 remove the high frequency components
from those signals, and send the resultant signals to an A/D
converter 12, which in turns converts those signals into digital
signals. Then, the digital signals are input to a logarithm
processing circuit 14, a .PHI. processing circuit 15 as attenuation
ratio processing means for processing attenuation ratios .PHI., and
an Hb concentration processing circuit 16 as hemoglobin Hb
concentration processing means. Reference numeral 13 indicates a
timing control circuit 13. The timing control circuit sends
necessary timing signals to the drive circuit 4, multiplexer 8 and
A/D converter 12 to control the operations of those circuits.
[0061] The logarithm processing circuit 14 processes I1, I2, and I3
as the output signals of the A/D converter 12 to produce the
logarithms lnI1, lnI2 and lnI3 of them. The .PHI. processing
circuit 15 extracts the pulsating components from the logarithms
lnI1, lnI2 and lnI3 obtained by the logarithm processing circuit
14, and processes .PHI.12=.DELTA.lnI1/.DELTA.lnI2 and
.PHI.13=.DELTA.lnI1/.DELTA.lnI3. The Bb concentration processing
circuit 16 solves simultaneous equations describing the ratios
.PHI., and obtains concentration ratios of oxyhemoglobin O2Hb,
deoxyhemoglobin RHb and carboxyhemoglobin COHb.
[0062] The computation expression in the Hb concentration
processing circuit 16 is as given by the following expression.
[0063] [Expression 4]
.PHI.12=.DELTA.A1/.DELTA.A2=[{square root}{square root over (
)}{(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)(Eo1.multidot.O2-
Hb+Er1.multidot.RHb+Ec1.multidot.COHb+F)}]/[{square root}{square
root over (
)}{(Eo2.multidot.O2Hb+Er2.multidot.RHb+Ec2.multidot.COHb)(Eo2.multidot.-
O2Hb+Er2.multidot.RHb+Ec2.multidot.COHb+F)}] (4)
.PHI.13=.DELTA.A1/.DELTA.A3=[{square root}{square root over (
)}{(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)(Eo1.multidot.O2-
Hb+Er1.multidot.RHb+Ec1.multidot.COHb+F)}]/[{square root}{square
root over (
)}{(Eo3.multidot.O2Hb+Er3.multidot.RHb+Ec3.multidot.COHb)(Eo3.multidot.-
O2Hb+Er3.multidot.RHb+Ec3.multidot.COHb+F)}] (4')
[0064] In the above expressions, RHb is a concentration ratio of
the deoxyhemoglobin, O2Hb is a concentration ratio of
oxyhemoglobin, and COHb is a concentration ratio of
carboxyhemoglobin. Eoi (i=1,2,3) is an absorption coefficient of
the oxyhemoglobin O2Hb. Eri (i=1,2,3) is an absorption coefficient
of the deoxyhemoglobin RHb. Eci(i=1,2,3) is an absorption
coefficient of the carboxyhemoglobin COHb. F is a scattering
coefficient, i=1, 2, 3 represent wavelengths .lambda.1, .lambda.2,
.lambda.3. Those coefficients Eoi, Eri, Eci and F are known.
Accordingly, the concentration ratios of the oxyhemoglobin O2Hb,
the deoxyhemoglobin RHb and the carboxyhemoglobin COHb can be
obtained in a manner that .PHI.2=.DELTA.A1/.DELTA.A2 and
.PHI.13=.DELTA.A1/.DELTA.A3 are measured, the measured ones are
substituted for the simultaneous equations, and those equations are
solved.
[0065] While the concentration ratios of the oxyhemoglobin O2Hb,
the deoxyhemoglobin RHb and the carboxyhemoglobin COHb are obtained
from .PHI.12 and .PHI.32 by solving the simultaneous equations, the
ratios may be obtained by referring to a table, which is prepared
in advance by using computations or experiment results.
[0066] A concentration ratio of the carboxyhemoglobin COHb may also
be obtained by using the following equations.
[0067] The blood is a light scattering material. Accordingly, an
equation describing an actual relation between an attenuation and
each concentration light absorbing materials in blood is
non-linear. Practically, the equations may be handled as linear
equations, however. For a non-light scattering material,
Lambert-Beer's law is generally applicable for that relation, and
the relation may be expressed by a linear equation, and expressed
by the following equations. However, those equations cannot be
applied to the blood having a light scattering nature directly.
[0068] [Expression 5]
.PHI.12[(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)]/[(Eo2.mult-
idot.O2Hb+Er2.multidot.RHb+Ec2.multidot.COHb)] (5)
.PHI.13=[(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)]/[(Eo3.mul-
tidot.O2Hb+Er3.multidot.RHb+Ec3.multidot.COHb)] (5')
[0069] The present invention newly presents the novel simplest
computation expressions instead of the conventional computation
expressions by Lambert-Beer, for example. To start, a population is
set up, and blood is actually sampled from the population.
Concentrations of various types of hemoglobins Hb are measured in a
highly accurately measuring manner, for example, by using a CO--
Oximeter. At this time, the pulsating waves are also measured,
whereby attenuation ratios .PHI. are processed. The values of those
measured hemoglobins Rb and the attenuation ratios .PHI. are
substituted for the following equations.
[0070] [Expression 6]
.PHI.12=A12.multidot.O2Hb+B12.multidot.RHb+C12.multidot.COHb
(6)
.PHI.13=A13.multidot.O2Hb+B13.multidot.RHb+C13.multidot.COHb
(6')
[0071] Where a plural number of measurements are carried out for
the population, the same number of the above equations ([Expression
6]) as that of the number of the measurements are prepared. The
equations ([Expression 6]) contain a total of six unknown
quantities, A12, B12, C12, A13, B13, and C13. Therefore, those
unknown quantities may be obtained by using six equations. By
substituting the thus processed unknown quantities for the
equations ([Expression 6]), the concentration ratios of the
hemoglobins Hb can be processed by using the attenuation ratios
.PHI. measured.
[0072] If the population is increased and more than six number of
computation expressions are set up, the coefficients satisfying all
the expressions cannot be obtained. If the functions of those
computation expressions are optimized and the coefficients are
processed, the optimum coefficients in the population can be
obtained. As the population becomes larger, the universality of the
computation expressions increases. A process of optimizing the
functions is as by the following expression 2n number of equations
are obtained.
[0073] [Expression 7]
.PHI.12i=A12.multidot.O2Hbi+B12.multidot.RHbi+C12.multidot.COHbi
(7)
.PHI.13i=A13.multidot.O2Hbi+B13.multidot.RHbi+C13.multidot.COHbi
(7')
[0074] A process in which the square sum of a difference between a
value .PHI.12ci obtained by processing the right sides of the
linear equations (Equation 7) and an actually measured value
.PHI.12mi is used as an objective function to be optimized, and is
minimized, can be realized by using the following expression.
[0075] [Expression 8]
f=.SIGMA.(i=1.about.n){((.PHI.12ci-.PHI.12mi).sup.2+(.PHI.13ci-.PHI.13mi).-
sup.2}=.SIGMA.(i=1.about.n){(A12.multidot.O2Hbi+B12.multidot.RHbi+C12.mult-
idot.COHbi-.PHI.12mi).sup.2+(A13.multidot.O2Hbi+B13.multidot.RHbi+C13.mult-
idot.COHbi-.PHI.13mi).sup.2} (8)
[0076] The coefficients A12, B12, C12, A13, B13, and C13, which
minimize f as the objective function of the equations ([Expression
8]) are obtained by using the steeptest descent method or the like,
whereby computation expressions may be determined.
[0077] In FIG. 1, signals representing concentration ratios of
oxyhemoglobin O2Hb, deoxyhemoglobin RHb and carboxyhemoglobin COHb,
which are processed by the above-mentioned processing process in
the Hb concentration processing circuit 16, are input to an Hb
concentration display unit 17 as hemoglobin Hb concentration
display means, a trend display unit 18 as trend display means, a
storage circuit 19 as storing means, and an alarm circuit 20 as
alarm display means. In this case, the Hb concentration display
unit 17, as shown in FIGS. 2 to 5, displays an arterial oxygen
saturation SpO2 and a carboxyhemoglobin COHb concentration.
[0078] FIG. 2 exemplarily shows an arrangement of the Hb
concentration display unit 17. In the display arranged as shown in
FIG. 2, SpO2(%)=O2Hb/(O2Hb+RHb) (%) as a functional oxygen
saturation or SpO2 (%)=O2Hb/(O2Hb+RHb+COBb)(%) as a fractional
oxygen saturation is selected by a functional/fractional display
select circuit 23 (see FIG. 1), and the selected one is displayed.
Specifically, the display, as shown, contains an oxygen saturation
SpO2 (%) numerical display section 30 and a COHb concentration (%)
numerical display section 31. The display further contains a
functional select switch/select status display section 34 and a
fractional select switch/select status display section 35, which
are provided in association with the oxygen saturation SpO2 (%)
numerical display section 30. The "functional oxygen saturation" or
"fractional oxygen saturation" is selected and the selected one is
displayed by use of the related section 34 or 35.
[0079] A numerical value to be displayed in the oxygen saturation
SpO2 (%) numerical display section 30 is the one processed using
three wavelengths or two wavelengths of red and near-infrared
lights as in the conventional case, which is selected by
3-wavelength/2-wavelength calculation display select circuit 24
(FIG. 1). in this case, to display the selected numerical value, a
COHb measuring button 36 is used. When the COHb measuring button 36
is turned on, concentrations of various types of hemoglobins
inclusive of carbon monoxide hemoglobin may be measured using three
wavelengths. When it is turned off, an oxygen saturation (SpO2) may
be measured as in the conventional manner using two
wavelengths.
[0080] FIG. 3 shows another display arrangement of the Hb
concentration display unit 17. In the display arranged as shown in
FIG. 3, the fractional SpO2 (%) is displayed in the oxygen
saturation SpO2 (%) numerical display section 30. The COHb
concentration (%) is indicated in any of three dangerous levels by
a dangerous level indicator 32. Two levels may be used in lieu of
three levels, for the purpose of a dangerous indication of the COHb
concentration. The remaining display arrangement is the same as
that of the FIG. 2 one. No further description of it will be given
here, while like portions are indicated by like reference numerals
in FIG. 2.
[0081] FIG. 4 shows yet another display arrangement of the Hb
concentration display unit 17. In the display arranged as shown in
FIG. 4, a dangerous level indicator 33 is used for indicating a
dangerous level of the COHb concentration (%). In the dangerous
level indicator 33, three dangerous levels shown in FIG. 3 are
expressed in terms of numerical values. The remaining display
arrangement is the same as of that the FIG. 2 one. No further
description of it will be given here, while like portions are
indicated by like reference numerals in FIG. 2.
[0082] A display of the Hb concentration display unit 17 may also
be designed as shown in FIGS. 5(A) and 5(B). In the display of FIG.
5(A), the abscissa represents the carboxyhemoglobin concentration,
the ordinate represents the fractional oxygen saturation
(oxyhemoglobin concentration), and the oblique line represents the
deoxyhemoglobin concentration. The display thus designed visually
presents three kinds of concentrations at a time. In the FIG. 5(A)
display, a point A indicates that the carboxyhemoglobin
concentration is 10%, the fractional oxygen saturation
(oxyhemoglobin concentration) is 85%, and the deoxyhemoglobin
concentration is 5%. A display designeddifferently from
thejust-mentioned one is shown in FIG. 5(B). In this display, the
abscissa represents the carboxyhemoglobin concentration, the
ordinate represents the deoxyhemoglobin concentration, and the
oblique line represents the fractional oxygen saturation
(oxyhemoglobin concentration). The display also visually presents
three kinds of concentrations at a time by use of the X-Y
coordinates.
[0083] In FIG. 1, the alarm circuit 20 generates an alarm by light,
sound, a message or the like when a concentration of
carboxyhemoglobin COHb is higher than a value set by an alarm
setting circuit 25. The alarm by light may be realized in the form
of the lighting of an alarm lamp, the flickering of the lamp for
indicating a dangerous level of the COHb concentration, the
flickering of the COHb concentration (%) indicator or the like. The
alarm by sound may be realized by an alarm sound representing the
presence of COHb. In this case, the COHb concentration may be
informed by varying the sound volume or the sound interval in
accordance with its concentration. The sound volume or interval may
be varied continuously in accordance with the concentration or
intermittently in accordance with a dangerous level. Additionally,
a sound synchronous with a pulsation may be changed in accordance
with the COHb concentration. In this case, frequency of the sound
or sounding duration may be changed in accordance with the presence
of COHb. In FIG. 1, reference numeral 26 designates a clock circuit
for clock operating the storage circuit 19.
[0084] A further display of the trend display unit 18, which may be
a liquid crystal display unit, is arranged as shown in FIGS. 6(A)
and 6(B). The display visually presents trends of SpO2 (%) and COHb
concentration (%). when events on the medical treatment applied to
an acute carbon monoxide poisoning patient or the like occurs,
information on the events is input to the hemoglobin concentration
determining apparatus from an event input circuit 21 (FIG. 1), and
displayed on the display screen of the trend display unit 18. The
event information may be oxygen inhalation, arrival at hospital,
blood sampling forcalibration, start of artificial respiration, and
start of anesthesia or the like. The attenuation ratio .PHI. and
the concentration ratios of oxyhemoglobin O2Hb, deoxyhemoglobin RHb
and carboxyhemoglobin COHb, which are processed in the Hb
concentration processing circuit 16, and the event information are
transmitted to and stored in the storage circuit 19. Even after the
power supply is interrupted or stopped, the data thus stored in the
storage circuit 19 is retained, and is displayed by the trend
display unit 18.
[0085] As show in FIG. 6(A), trends of the concentrations of the
hemoglobins may be displayed for both the functional and the
fractional oxygen saturations (SpO2). The concentrations of the
oxyhemoglobin O2Hb, deoxyhemoglobin RHb and carboxyhemoglobin COHb
may be displayed in terms of t, together with the event information
(FIG. 6B). In the apparatus, the data that is stored in the storage
circuit 19 may be sent to an external device, e.g., personal
computer, through an external interface (FIG. 1).
[0086] The hemoglobin concentration determining apparatus shown in
FIG. 1 includes a value input circuit for calibration 22 for
inputting an in-blood light absorbing material concentration, which
is measured by the blood sampling. The data from the value input
circuit for calibration 22 is input to the Hb concentration
processing circuit 16. The Hb concentration processing circuit 16
performs calibration computations on the oxyhemoglobin O2Hb,
deoxyhemoglobin RHb and carboxyhemoglobin COHb. The calibration
computation may be performed in the following way.
[0087] When a change of an attenuation by a pulsation of a living
tissue, which is caused by a pulsation of blood is allowed for, a
ratio .PHI. of the attenuations is expressed by (as described in
JP-A-8-322822)
[0088] [Expression 9]
.PHI.12=.DELTA.A1/.DELTA.A2=[{square root}{square root over (
)}{(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)(Eo1.multidot.O2-
Hb+Er1.multidot.RHb+Ec1.multidot.CORb+F)}-Ex]/[{square root}{square
root over ( )}{(Eo2.multidot.O2Hb+Er2.multidot.RHb
+Ec2.multidot.COHb)(Eo2.mul-
tidot.O2Hb+Er2.multidot.RHb+EC2.multidot.COHb+F)}-Ex] (9)
.PHI.13=.DELTA.A1/.DELTA.A3=[{square root}{square root over
(])}{(Eo1.multidot.O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb)(Eo1.multidot.-
O2Hb+Er1.multidot.RHb+Ec1.multidot.COHb+F)}-Ex]/[{square
root}{square root over
(])}{(Eo3.multidot.O2Hb+Er3.multidot.RHb+Ec3.multidot.COHb)(Eo3.mult-
idot.O2Hb+Er3.multidot.RHb+Ec3.multidot.COHb+F)}-Ex] (9')
[0089] In the above equations, EX is a term indicating an
attenuation caused by the pulsation of the pure tissue, and is
unknown.
[0090] The unknown quantity EX may be determined by substituting
the values obtained by sampling blood and measuring it for the
above equations. Subsequently the simultaneous equations containing
the thus determined unknown quantity EX are used, and highly
accurate measurement results based on the pure tissue pulsation
will be produced. Further, if the computation is carried out over
again on the attenuation ratios .PHI. or the concentration rations
of hemoglobins that are stored in the storage circuit 19 before the
values for calibration are input by using the in-blood material
concentration values obtained by sampling blood and measuring it,
highly accurate measurement results can be obtained
retrospectively.
[0091] Another calibration process will be described. The
calibration process is applied for a calibration on an error caused
by other light absorbing materials in blood, such as methemoglobin
and bilirubin. A computation expression constructed while allowing
for methemoglobin MeHb is given by
[0092] [Expression 10]
.PHI.12=.DELTA.A1/.DELTA.A2=[{square root}{square root over (
)}{(Eo1.multidot.O2Hb+Er1.multidot.RHb+Em1.multidot.MetHb+Ec1.multidot.CO-
Hb)(Eo1.multidot.O2Hb+Er1.multidot.RHb+Em1.multidot.MetHb+Ec1.multidot.COH-
b+F)}-Ex]/[{square root}{square root over (
)}{(Eo2.multidot.O2Hb+Er2.mult-
idot.RHb+Em2.multidot.MetHb+Ec2.multidot.COHb)(Eo2.multidot.O2Hb+Er2.multi-
dot.RHb+Er2.multidot.MetHb+Ec2.multidot.COHb+F)}-Ex] (10)
.PHI.13=.DELTA.A1/.DELTA.A3=[{square root}{square root over (
)}{(Eo1.multidot.O2Hb+Em1.multidot.RHb+Em1.multidot.MetHb+Ec1.multidot.CO-
Hb)(Eo1.multidot.O2Hb+Er1.multidot.RHb+Em1.multidot.MetHb+Ec1.multidot.COH-
b+F)}-Ex]/[{square root}{square root over (
)}{(Eo3.multidot.O2Hb+Er3.mult-
idot.RHb+Em3.multidot.MetHb+Ec3.multidot.COHb)(Eo3.multidot.O2Hb+Er3.multi-
dot.RHb+Em3.multidot.MetHb+Ec3.multidot.COHb+F)}-Ex] (10')
[0093] The unknown quantity EX may be processed by substituting
measured hemoglobins O2Hb, RHb, COHb, and MetHb for the above
equations. Further, the concentration ratios of the hemoglobins
O2Hb, RHb and COHb may be obtained by substituting the processed
unknown quantity EX and the methemoglobin MetHb measured by the
blood sampling method for the equations, and solving the
simultaneous equations on the assumption that EX and MetHb are
constant. Incidentally, in an alternative computation, terms of
bilirubin are incorporated into the above equations, and a
bilirubin value measured by the blood sampling method is
substituted for the equations. The same thing is valid for any of
other in-blood light absorbing materials.
[0094] While the preferred embodiment of the invention has
specifically be described, it should be understood that the present
invention is not limited to the embodiment mentioned above, but may
variously be modified, altered and changed within true spirits of
the invention.
[0095] As seen from the foregoing description, an apparatus for
determining concentrations of hemoglobins comprises: a light source
for emitting lights of at least three different wavelengths, a
first wavelength in a near-infrared wavelength region of 790 to
1000 nm,, a second wavelength in a red wavelength region of 640 to
675 nm, and a third wavelength in an orangy red wavelength region
of 590 to 660 nm; light receiving means for receiving lights that
are emitted by the light source and transmitted through or
reflected by a living tissue; attenuation ratio processing means
for processing an attenuation ratio .PHI. on the wavelengths based
on variations of signals associated with the wavelengths output
from the light receiving means, which variations are caused by a
pulsation of blood; and concentration ratio processing means for
processing concentration ratios of at least oxyhemoglobin,
deoxyhemoglobin and carboxyhemoglobin based on the output signals
from the attenuation ratio processing means. Accordingly, the
apparatus can detect a change of the transmitted light by a change
of the carboxyhemoglobin COHb at good S/N ratio, and can easily
discriminate between the carboxyhemoglobin COHb and the
deoxyhemoglobin RHb, and hence can perform a proper measurement of
carboxyhemoglobin COHb.
[0096] Where the hemoglobin concentration determining apparatus is
used, in measuring SpO2 when COHb is not present in blood, the
measurement using two wavelengths is better than that using three
wavelengths in the measuring accuracy since the former is based on
the data accumulated for a long time. To diagnose a patient not
suffering from carbon monoxide poisoning, the COHb measuring button
36 is turned off, the apparatus highly accurately measures an
oxygen saturation (SpO2) by using two wavelengths as in the
conventional case. To diagnose a patient who may suffer from carbon
monoxide poisoning, the COHb measuring button 36 is turned on, the
apparatus measures concentrations of various types of hemoglobins
including carboxyhemoglobin by using three wavelengths. A simple
display of presence or absence of carbon monoxide or a dangerous
level, not a precise display of a carbon monoxide concentration in
steps of 1%, will be very useful when an ambulance man decides if
the patient is to be transported to a hospital installed with
hyperbaric oxygen therapy, or when the medical staff decides how
the medical treatment progresses. Further, when a concentration of
a light absorbing material in blood, measured by the blood sampling
method, is used as a calibrated value, a concentration of each
hemoglobin can be measured more accurately.
[0097] The best method of measuring a concentration of
carboxyhemoglobin COHb in blood is a method of measuring the same
by the blood sampling method using the CO-oximeter. When highly
reliable, measured values obtained by such a method are further
calibrated, the accuracy of the measured values is further
increased. It is a common practice that oxygen inhalation is used
for the treatment of the patient suffering from the acute carbon
monoxide poisoning. In such a treatment, the apparatus of the
invention enables one to highly reliably monitor a process in which
the concentration of carboxyhemoglobin COHb progressively
decreases.
[0098] When the apparatus for determining concentrations of
hemoglobins is used, the concentrations of three hemoglobins, i.e.,
carboxyhemoglobin concentration, deoxyhemoglobin concentration and
fractional oxygen saturation (oxyhemoglobin concentration), are
displayed on the X-Y coordinates, and hence one can visually grasp
those concentrations at a time.
[0099] In the apparatus, a change of each hemoglobin concentration
with time may be checked together with an event marker or the like
concerning the treatment for the patient. The data obtained is very
useful in mapping out the course of treatment. Further, the effects
of the treatment can visually be checked.
[0100] With the event information on a trend graph provided by the
storing functions and event marker functions , the subsequent
medical treatment of a patient of acute carbonate monoxide
poisoning who has been transported into a hospital is made easy.
When the patient resprirates the air spontaneously, a period that
the quantity of carboxyhemoglobin COHb is reduced to half quantity
is about 4 hours. It is about 80 minutes by the oxygen inhalation,
and is about 14 minutes by the positive pressure ventilation by
oxygen. It is vital to rapidly reduce the carboxyhemoglobin
concentration in blood by the oxygen inhalation. The function of
storing and reproducing a change of the in-blood hemoglobin Hb
concentration of the patient for a period from a time that a
patient of carbon monoxide poisoning is found till he is
transported to the hospital, and the history of oxygen inhalation,
provides important data in mapping out the course of medical
treatment.
* * * * *