Patent Grant
6990426
1. Field of the Invention
The present invention relates to a diagnostic method and apparatus using light. More particularly, the present invention relates to a method and apparatus for measuring blood hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels using light.
2. Description of the Related Art
Hemoglobin in red blood cells is responsible for supplying oxygen throughout the human body and is essential for the normal function of every cell in the body. A reduced supply of oxygen to the body restricts the intercellular energy metabolism in tissues, and a lack of oxygen for a prolonged period of time results in death. Hemoglobin content is used as a measure of anemia and is measured to qualify a blood donor and to determine the volume of blood that may safely be taken from a blood donor.
There is a need for real-time monitoring of a patient's condition by measuring hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels, especially in patients that are bleeding as the result of a traffic accident and in patients in need of a surgical operation. In addition, there is a need for introducing a convenient method that enables a health care provider to check frequently biological conditions of children and pregnant females, in particular, by measuring these parameters.
Conventionally, hemoglobin concentration is measured in a medical institute for therapeutic or prophylactic purposes through chemical analysis of blood drawn from the body. The measurements of pulse rate, respiration rate, or degree of aging of blood vessels are typically conducted only by health care providers. Therefore, a convenient method enabling the general public to personally measure each of these parameters at home is required.
The present invention provides a method and apparatus for measuring blood hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels using light.
According to an aspect of the present invention, there is provided a diagnosis apparatus using light, including an input/output unit for receiving a command for measurement from a user and for providing information on the result of a measurement to the user; a control unit for receiving the command for measurement from the input/output unit and for generating a control signal; a light generating unit for generating at least two light beams, each light beam having an initial intensity, for measurement according to the control signal; a light receiving unit for detecting the intensity of each of the at least two light beams after transmission through an object that is subject to measurement and for converting the received light beams into electrical signals; and a data processing unit for processing the electrical signals received from the light receiving unit and for outputting information on the result of a predetermined measurement to the input/output unit.
Preferably, the light generating unit includes a digital-to-analog converter for receiving the control signal from the control unit and for converting the received control signal into an analog signal; a light emitting diode driver for driving a light emitting diode to generate the at least two light beams according to the analog signal; and a light radiator for radiating the generated light beams onto the object.
Preferably, the light receiving unit includes a photodetector for detecting the intensities of the at least two light beams after transmission through the object and for converting the detected light beam intensities into analog electrical signals; a low-pass filter for filtering out a high frequency component of the analog electrical signals (representing the intensity of the at least two light beams received from the photodetector); and an analog-to-digital converter for converting the analog electrical signals (representing the intensity of the light beams, from which the high-frequency component has been removed) into digital electrical signals.
In one embodiment of the present invention, the data processing unit may include a ratio calculation portion for receiving the electrical signals (representing the intensity of the at least two light beams received by the light receiving unit) from the light receiving unit and for calculating, for each wavelength of the at least two light beams, a ratio of the intensity of the light received by the light receiving unit with respect to the initial intensity of the light radiated from the light generating unit; and a hemoglobin concentration and oxygen saturation calculation portion for calculating a hemoglobin concentration value using the ratio calculated by the ratio calculation portion based on a correlation between light intensity variations and hemoglobin concentrations and for calculating an oxygen saturation value using the calculated hemoglobin concentration value.
In another embodiment of the present invention, the data processing unit may include a pulse rate calculation portion for receiving the electrical signals (representing the intensity of the at least two light beams output from the light receiving unit) from the light receiving unit, for extracting a pulse wave signal having a frequency corresponding to an average pulse rate per minute for humans from the received electrical signals, and for calculating a pulse rate based on an average time interval between peaks detected from the extracted pulse wave signal.
In yet another embodiment of the present invention, the data processing unit may include a respiration rate calculation portion for receiving the electrical signals (representing the intensity of the at least two light beams output from the light receiving unit) from the light receiving unit, for extracting a respiration signal having a frequency corresponding to an average respiration rate per minute for humans from the received electrical signals, and for calculating a respiration rate based on an average time interval between peaks detected from the extracted respiration signal.
In still another embodiment of the present invention, the data processing unit may include a degree of aging of blood vessels calculation portion for receiving the electrical signals (representing the intensity of the at least two light beams output from the light receiving unit) from the light receiving unit, for extracting a first pulse wave signal having a frequency corresponding to an average pulse rate per minute for humans from the received electrical signals, for differentiating the extracted first pulse wave signal into a second pulse wave signal to detect inflection points therein, for calculating a diagnostic index for the degree of aging of blood vessels using the values of the inflection points, and for calculating a degree of aging of blood vessels using the calculated diagnostic index, based on a correlation between the degrees of aging of blood vessels and diagnostic indices therefor.
In addition, the data processing unit may further include a data storage portion for storing measured results and for outputting to the input/output unit a calculated result according to a control signal of the control unit.
According to another aspect of the present invention, there is provided a diagnosis method using light, including (a) receiving a command for measurement from a user; (b) generating a control signal according to the received command for measurement; (c) generating at least two light beams, each light beam having an initial intensity, for measurement according to the control signal; (d) radiating the at least two light beams onto an object that is subject to measurement, detecting the intensities of the at least two light beams after transmission through the object, and converting the detected intensities of the at least two light beams into electrical signals; and (e) processing the electrical signals to obtain information on the result of a predetermined measurement.
Preferably, generating the at least two light beams includes (c1) receiving the control signal and converting the received control signal into an analog signal; (c2) generating the at least two light beams according to the analog signal; and (c3) radiating the generated light beams onto the object.
Preferably, radiating the light beams onto an object includes (d1) detecting the intensities of the at least two light beams after transmission through the object and converting the detected light beam intensities into analog electrical signals; (d2) filtering out a high frequency component of the analog electrical signals (representing the intensity of the transmitted light beams); and (d3) converting the analog electrical signals (representing the intensity of the light beams, from which the high-frequency component has been removed) into digital electrical signals.
In one embodiment of the present invention, processing the electrical signals may include (e1) calculating, for each wavelength of the at least two light beams, a ratio of the intensity of the light beam detected in (d) with respect to the initial intensity of the light generated in (c); (e2) calculating a hemoglobin concentration value using the ratio calculated in (e1) based on a correlation between light intensity variations and hemoglobin concentrations and calculating an oxygen saturation value using the calculated hemoglobin concentration value.
In another embodiment of the present invention, processing the electrical signals may include extracting a pulse wave signal having a frequency corresponding to an average pulse rate per minute for humans from the electrical signals obtained in (d); and calculating a pulse rate based on an average time interval between peaks detected from the extracted pulse wave signal.
In yet another embodiment of the present invention, processing the electrical signals may include extracting a respiration signal having a frequency corresponding to an average respiration rate per minute for humans from the electrical signals obtained in (d); and calculating a respiration rate based on an average time interval between peaks detected from the extracted respiration signal.
In still another embodiment of the present invention, processing the electrical signals may include extracting a first pulse wave signal having a frequency corresponding to an average pulse rate per minute for humans from the electrical signals obtained in (d); differentiating the extracted first pulse wave signal into a second pulse wave signal to detect inflection points therein; calculating a diagnostic index for the degree of aging of blood vessels using the values of the inflection points; and calculating a degree of aging of blood vessels using the calculated diagnostic index, based on a correlation between the degrees of aging of blood vessels and diagnostic indices therefor.
The diagnosis method may further include providing the result of the predetermined measurement to the user, wherein the user may be remotely located from the object subject to measurement. The diagnosis method may also further include storing the information on the result of the predetermined measurement.
In any of the aspects and embodiments of the present invention, preferably, the at least two light beams have different wavelengths. Also preferably, the at least two light beams are selected from a range of wavelengths in which the extinction coefficient for water is smaller than that of hemoglobin and have a wavelength no longer than 1300 nm. Preferably, the at least two light beams are isobestic and each has a wavelength selected from the group consisting of 422 nm, 453 nm, 499 nm, 529 nm, 546 nm, 569 nm, 584 nm, 805 nm, and 1300 nm.
Another feature of an embodiment of the present invention is to provide a computer readable medium having embodied thereon a computer program for any of the above-described diagnosis methods.
The above features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:
Korean Patent Application No. 2002-14277, filed on Mar. 16, 2002, and entitled: “Diagnostic Method and Apparatus Using Light,” is incorporated by reference herein in its entirety.
Several embodiments of a diagnosis method and apparatus for measuring blood hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels using light, according to the present invention, will now be described with reference to the appended drawings.
In operation, a user provides the input/output unit 101 a parameter to be measured, such as blood hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, degree of aging of blood vessels (hereinafter “DOA”). The input/output unit 101 informs the user of the result of a measurement of the input parameter. The input/output unit 101 may use a button, a mouse, a keyboard, or the like as an input device and may use a computer monitor, a liquid crystal display (LCD), or other display as an output device for providing the information regarding the result of the measurement to the user. Alternatively, information on the result of a measurement may be transmitted via, for example, an RS232 port to an external personal computer (PC), a personal digital assistant (PDA), or the like. Accordingly, the user may be remotely located from the patient and the object subject to the measurement.
The control unit 102 receives a command to measure a predetermined parameter from the input/output unit 101 and transmits information on the parameter to the light generating unit 103, the light receiving unit 104, and the data processing unit 105. The control unit 102 also verifies the operation of each unit of the diagnosis apparatus.
The light generating unit 103 generates at least two light beams having predetermined wavelengths for measurement according to the information on the parameter received from the control unit 102. A detailed configuration of the light generating unit 103 is shown in
Referring back to
Referring back to
Referring to
The ratio calculation portion 401 receives the digital intensity signals for the received light beams output from the light receiving unit 104 and, for each of the light beams, calculates a ratio of the intensity of the light received by the light receiving unit 104 with respect to the initial intensity of the light radiated from the light generating unit 103 onto the object that was subjected to the measurement.
The hemoglobin concentration and oxygen saturation calculation portion 402 calculates a hemoglobin concentration value using the ratio calculated by the ratio calculation portion 401 based on a correlation between light intensity variations and hemoglobin concentrations, and calculates an oxygen saturation value using the calculated hemoglobin concentration value. A method for calculating oxygen saturation following the calculation of hemoglobin concentration is briefly described below. Oxygen saturation, which is expressed as a percentage of the concentration of oxyhemoglobin bound to oxygen with respect to total hemoglobin concentration, is measured to quantify the amount of oxygen saturated in blood for the normal function of body cells. To measure oxygen saturation, red light and infrared light are transmitted through biological tissues, the absorbance for each wavelength of the radiated lights is measured using pulses of arterial blood, and a ratio of the measured absorbances is calculated as the oxygen saturation. Most of the light radiated on the human body is absorbed by bones, tissues, etc., which are not involved in pulsing, via predetermined travelling paths, and only 1–2% of the light radiated is absorbed by arterial blood, which induces pulses. By measuring the intensity of the light transmitted through the body, the light absorbencies of the pulsing components and the non-pulsing components for each wavelength of the radiated light beams can be calculated, which will give the light absorbance of hemoglobin present in the arterial blood. As a result, the oxygen saturation of hemoglobin can be determined from the absorbance ratio between the two wavelengths of light.
The pulse rate calculation portion 403 receives the digital signals corresponding to the intensities of the received light beams from the light receiving unit 104, extracts a pulse wave signal having a frequency corresponding to an average pulse rate per minute for humans from the received digital signal, and calculates a pulse rate per minute based on an average time interval between peaks detected from the extracted pulse wave signal.
More specifically, the pulse rate calculation portion 403 receives the digital signals corresponding to the intensities of the light beams sequentially transmitted through a predetermined body site to be measured, e.g., a finger, and extracts only a pulse wave signal having a frequency in accordance with an average pulse rate for humans from the received signals using, for example, software such as a filtering program. Differentiation is performed on the pulse wave signal passed through a filter, and inflection points, at which the slope changes from positive to negative, are detected from the differentiated pulse wave signal. When an inflection point has a value greater than a predetermined threshold value, the inflection point is stored as a peak. An average time interval between detected peaks is calculated, and the number of peaks in a 60 second interval is calculated based on the average time interval as a pulse rate.
A received signal, as described above, may be classified into pulse waves, velocity pulse waves, or acceleration pulse waves according to the signal processing technique applied to the received signal. In general, pulse waves refer to the original waveform of body pulses and are used to characterize the original body pulses. However, the original body pulses have too smooth a waveform for variations to be detected. To compensate for this smoothness, the original body waves are differentiated for clinical applications. These differential body waves are called “velocity pulse waves.” Velocity pulse waves are used to analyze variations in the waveform of the original body waves. Velocity pulse waves, i.e., differential pulse waves, are used in currently available pulse wave detectors. However, variations in the original body waves cannot be fully analyzed with velocity pulse waves. For this reason, velocity pulse waves are further differentiated into “acceleration pulse waves” for clinical uses. Recent advances in the medical engineering field, especially in the diagnosis of circulatory system disorders, have put greater importance on the use of electrocardiograms, photocardiograms, cardiac catheterizations, and the like. Although various experiments have been conducted on pulse waves, the consequence of pulse waves as a diagnostic index tends to be underestimated due to the simple pulse waveform and its nature of being susceptible to a number of factors. Pulse waves are considered to be significant only to some extent in a limited number of peripheral vascular diseases. However, based on the possibility of measuring cardiac failure by the palpation of the radial artery, research on pulse waves as a measure of cardiac reserve or cardiac insufficiency has been conducted. Measuring cardiac failure by the palpation of the radial artery is based on the fact that certain types of cardiac disorders lead to a typical alternation in the pulse waveform resulting from abnormal hemokinetic behaviors. In addition, pulse waves can be used as a diagnostic index for vascular diseases, such as arterial occlusive disorders, alterations in vascular elasticity, etc.
An example of a pulse wave is illustrated in
Referring back to
The method for calculating the respiration rate per minute will be described in detail. A respiration signal having a frequency in accordance with the average respiration rate for humans is extracted from a pulse wave signal using a bandpass filter. This bandpass filter used may be implemented using software.
Normal adults breathe 10–20 times a minute in a stable state and up to about 45 times a minute when exercising. Therefore, the respiration signal has a relatively low frequency of about 0.1–0.5 Hz with respect to the pulse wave signal and can be separated from the pulse wave signal using an appropriate bandpass filter. Inflection points, at which the slope changes from positive to negative, are detected from the separated respiration signal that has passed a digital filter. Since one inflection point corresponds to one breath, the respiration rate per minute can be calculated by counting the number of inflection points in a 60 second interval.
The DOA calculation portion 405 receives the digital signals corresponding to the intensities of the received light beams, extracts a first pulse wave signal having a frequency in accordance with the average pulse rate for humans, differentiates the extracted first pulse wave signal into a second pulse wave signal to detect inflection points therein, calculates a diagnostic index for the degree of aging of blood vessels using the values of the inflection points, and calculates a degree of aging of blood vessels for a subject using the calculated diagnostic index, based on a correlation between the degrees of aging of blood vessels and diagnostic indices therefor.
The method for calculating a degree of aging of blood vessels according to the present invention will now be described in detail with reference to
Referring back to
By using the methods described above, in step 705, hemoglobin concentration and oxygen saturation may be calculated, in step 706 pulse rate and respiration rate may be calculated, or, in step 707, degree of aging of blood vessels may be calculated. Next, in step 708, the calculated results may be stored and provided to the user.
Light beams used in the present invention for measurement are selected from a range of wavelengths in which the extinction coefficient for water is smaller than that of hemoglobin, i.e., from wavelengths no longer than 1300 nm. At least two isobestic wavelengths, i.e., a wavelength having the same extinction coefficient for any forms of hemoglobin irrespective of whether hemoglobin is in oxidized or reduced form, are selected from that wavelength range. Accordingly, light beams having a wavelength of 422 nm, 453 nm, 499 nm, 529 nm, 546 nm, 569 nm, 584 nm, 805 nm, or 1300 nm may be used in the present invention.
The above embodiments of the present invention may be embodied in a general purpose digital computer by running a program from a computer readable medium, which includes but is not limited to storage media such as magnetic storage media (e.g., ROM's, floppy disks, hard disks, etc.), optically readable media (e.g., CD-ROMs, DVDs, etc.), and carrier waves (e.g., transmissions over the Internet).
The present invention effects measurements of hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels using the same apparatus in a non-invasive manner. A diagnosis apparatus using light, according to the present invention, is convenient to carry and use and enables simultaneous real-time monitoring of hemoglobin concentration, oxygen saturation, pulse rate, and respiration rate.
A diagnosis apparatus using light, according to the present invention, is able to measure multiple parameters including hemoglobin concentration, oxygen saturation, pulse rate, respiration rate, and degree of aging of blood vessels, without withdrawing blood from a patient, and is very convenient to use as compared to conventional apparatuses that separately measure each of the parameters separately. In addition, the ability to measure at least the five parameters listed above using a single apparatus is cost effective.
According to the present invention, since only one photodetector is used, measurements can be achieved with a higher degree of accuracy. Measurements of such parameters of interest are less affected by body tissues excluding blood vessels. With the installation of a communication device in a diagnosis apparatus according to the present invention, the result of a measurement performed at home can be directly transmitted to a hospital via the Internet. Therefore, there is no inconvenience of going to a hospital for a checkup. A patient at home may be directly informed of his/her state of health by a doctor at a hospital or other remote location.
Preferred embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2002-0014277 | Mar 2002 | KR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3593704 | Schwab | Jul 1971 | A |
| 4869253 | Craig et al. | Sep 1989 | A |
| 5137023 | Mendelson et al. | Aug 1992 | A |
| 5206807 | Hatke et al. | Apr 1993 | A |
| 5273036 | Kronberg et al. | Dec 1993 | A |
| 5482036 | Diab et al. | Jan 1996 | A |
| 5499627 | Steuer et al. | Mar 1996 | A |
| 5800348 | Kaestle | Sep 1998 | A |
| 5830137 | Scharf | Nov 1998 | A |
| 5833602 | Osemwota | Nov 1998 | A |
| 5862805 | Nitzan | Jan 1999 | A |
| 5941837 | Amano et al. | Aug 1999 | A |
| 6011985 | Athan et al. | Jan 2000 | A |
| 6067462 | Diab et al. | May 2000 | A |
| 6325761 | Jay | Dec 2001 | B1 |
| 6398727 | Bui et al. | Jun 2002 | B1 |
| 6702752 | Dekker | Mar 2004 | B2 |
| Number | Date | Country |
|---|---|---|
| 1 120 427 | Apr 1996 | CN |
| 0 555 553 | Aug 1993 | EP |
| 0 555 553 | Aug 1993 | EP |
| 1-232928 | Sep 1989 | JP |
| 5-269116 | Oct 1993 | JP |
| 6-507485 | Aug 1994 | JP |
| 7-213500 | Aug 1995 | JP |
| 9-135819 | May 1997 | JP |
| 10-216114 | Aug 1998 | JP |
| 10-216115 | Aug 1998 | JP |
| 2000-23928 | Jan 2000 | JP |
| 3054437 | Jun 2000 | JP |
| 2000-217797 | Aug 2000 | JP |
| 2002-65621 | Mar 2002 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20030236647 A1 | Dec 2003 | US |
