JPH0666633U - Pulse oximeter - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a pulse oximeter which uses a wide-wavelength light source for a light emitting section and is equipped with three or more types of filters and a light receiving section and which is suitable for measuring oxygen saturation of arterial blood with higher accuracy. A finger insertion part 8 is provided on one cross section of a pulse oximeter fingertip mounting device 1, and a light emitting part 2 of a wide-wavelength light source 2a connected to a lead wire 6 is provided above the finger insertion part 8 and the light emitting part 2 is opposed to the light emitting part 2. The filters 3A, 3B and 3C for filtering light of three or more kinds of predetermined wavelengths and the photodiodes of the light receiving portions 4A, 4B and 4C corresponding to these filters are arranged below the finger insertion part 8 to obtain a correct result. The transmitted light from the photodiode 4A,
A pulse oximeter configured to be converted into signals at 4B and 4C, respectively, and to be coupled to the pulse oximeter main body 10 arranged outside the pulse oximeter fingertip mounting device 1 by the lead wire 5 together with the lead wire 6 described above.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pulse oximeter suitable for continuously measuring arterial oxygen saturation.

[0002]

[Prior art]

 For example, when a patient is prone to respiratory disorders such as anesthesia, artificial respiration, oxygen administration, surgery, and post-surgical treatment, monitoring of oxygen content in arterial blood is indispensable and frequently performed.

For this reason, a blood sampling test was performed in the past. However, although there are risks such as blood clots, and data on the patient's oxygen content at the time of blood sampling, it was There was a problem that it could not be evaluated.

On the other hand, an arterial blood oxygen saturation measuring device (hereinafter referred to as a pulse oximeter), which has recently been rapidly developed and put into practical use, uses a spectroscopic analysis to analyze the change in the absorbance of transmitted light accompanying the pulsation of arterial blood at the fingertip. By using the device to continuously measure the arterial blood oxygen saturation (hereinafter referred to as SpO ₂ ), the drawbacks of the arterial blood gas analysis by traditional blood sampling were overcome.

That is, the conventional pulse oximeter is a fingertip mounting device 11 including light emitting diodes (LEDs) 12a and 12b as light sources of two kinds of wavelengths shown in FIG. 3 and a light receiving element (photodiode) 14. And a pulse oximeter including an oscillation substrate (OSC) for alternately emitting the light emitting diodes 12a and 12b and a microcomputer for activating arithmetic processing, display, recording, alarm device, etc. by a signal from the light receiving element 14. It consists of the main body 20.

The pulse oximeter basically utilizes the fact that the hemoglobin absorbance varies depending on the saturation of oxygen and the wavelength of light. Therefore, the absorbance of only the change in the thickness of the arterial blood layer of the finger 7 to be measured is measured. SpO ₂ can be used as a target for measurement, and is not affected by the color and thickness of fingertip tissue, the coexistence of venous blood, and the like. Can be obtained as a function of the ratio of the logarithmic difference in the amount of transmitted light.

[0007]

[Problems to be solved by the device]

However, even with such a pulse oximeter, there are some problems in its actual measurement. One of the major ones is that SpO ₂ is displayed as the ratio of oxyhemoglobin to total hemoglobin, but carbon monoxide hemoglobin (HbCO) and methemoglobin (MetHb) contained in total hemoglobin are not measured, and the denominator is 1 Like oxyhemoglobin (HbO ₂ ) and reduced hemoglobin (RHb)

[0008]

[Equation 1]

Alternatively, as in Equation 2, HbCO and MetHb handle the correction value added as a constant.

[0010]

[Equation 2]

In view of the above, the present invention provides a pulse oximeter capable of more accurately obtaining the oxygen saturation of arterial blood.

[0012]

[Means for Solving the Problems]

 The pulse oximeter of the present invention is, for example, as shown in FIG. 1, a light emitting section 2 provided with a wide wavelength light source 2a, light receiving sections 4A, 4B, 4C for receiving light from the light emitting section 2, and these. And a finger insertion part 8 provided between the light receiving parts 4A, 4B and 4C of the light receiving part 4A, 4B, 4C, and the light from the light emitting part 2 through the plural filters 3A, 3B and 3C. It is designed to be supplied to 4C.

[0013]

[Action]

According to the pulse oximeter of the present invention, the wide-wavelength light source 2a emits light in a wide-wavelength band, transmits the fingertip, and then passes the light through the plurality of filters 3A, 3B, 3C having the measurement wavelengths. The transmitted light of the wavelength is received by the light receiving parts 4A, 4B, 4C arranged behind the filters 3A, 3B, 3C, and not only oxidized hemoglobin (HbO ₂ ) and reduced hemoglobin (RHb) but also carbon monoxide is received. The amount of hemoglobin (HbCO) and methemoglobin (MetHb) can also be measured, and more accurate SpO ₂ can be obtained.

[0014]

【Example】

 An embodiment of the pulse oximeter of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 3 described above are designated by the same reference numerals, and detailed description thereof will be omitted.

The pulse oximeter fingertip attachment device 1 analyzes changes in absorbance of transmitted light in three wavelength bands due to pulsation of arterial blood in a fingertip or the like to continuously measure SpO _2. Therefore, the fingertip attachment device 1 generally has a finger insertion portion 8 having an opening on one side into which the tip (hereinafter referred to as the finger to be measured) 7 of the index finger is inserted.

The diameter of the finger insertion portion 8 has such a thickness that the finger 7 to be measured can be smoothly inserted, and the entrance portion 8A thereof is made of an elastic material such as rubber and is made of the material to be measured 7. In addition to controlling the position, a light-shielding member 9A that closes the gap between the finger 7 to be measured and the finger insertion part 8 is arranged so that ambient light enters the finger insertion part 8 during measurement, which affects the measurement accuracy. Prevent from exerting.

The light emitting unit 2 is arranged at an upper portion of the finger insertion portion 8 and a central portion of the inserted measured finger 7 such as a portion just above the central portion of the index fingernail. The light emitting section 2 is provided with a wide wavelength light source for emitting light in a wide wavelength band, for example, a tungsten filament light emitting body 2a so as to emit light with a wavelength of, for example, 600 nm to 1000 nm.

Further, for example, three filters 3A, 3B, 3C are arranged at a central portion of the finger 7 to be measured at a lower portion of the finger insertion portion 8 and a portion corresponding to an inner side of a forefinger of the forefinger received by the light emitting portion 2. To do. This filter 3A is supposed to pass 660 nm (red light) which seems to be the most effective in the spectrum analysis, the filter 3C is supposed to pass 940 nm (infrared light), and the filter 3B is placed between them. It has a characteristic of transmitting light of 805 nm.

Photodiodes 4A, 4B and 4C are provided which correspond to these filters 3A, 3B and 3C and detect the light passing through these filters 3A, 3B and 3C.

A detection signal corresponding to the amount of light obtained in each of the photodiodes 4 A, 4 B and 4 C is supplied to the pulse oximeter body 10 via the lead wire 5, respectively. That is, together with the lead wire 6 connected to the rear portion of the light emitting portion 2 described above, the finger tip mounting device 1 is inserted from the lead wire inlet port 8C on the side opposite to the entrance portion 8A of the finger insertion portion 8 of the finger tip mounting device 1. And is connected to the pulse oximeter body 10 via the relay connector 16, for example.

The operation of the pulse oximeter having the above configuration will be described below. For example, the index finger of the left hand is used as the measured finger 7 and is inserted into the finger insertion portion 8 of the pulse oximeter fingertip mounting device 1.

The inside of the finger tip surely contacts the lower portion of the finger insertion portion 8, and the entrance portion 8A of the finger insertion portion 8 surely covers the circumference of the finger to be measured 7 by the light shielding member 9A. To prevent the ambient light from entering the inside of the finger insertion portion 8 through the gap.

A voltage is applied to the light emitting portion 2 from the pulse oximeter main body 10 through the lead wire 6, and the wide wavelength light source 2a emits red light to infrared light having a wavelength of 600 to 1000 nm, and is related to the size and state of the fingertip. It must be light that has sufficient brightness to allow light to pass through.

The light emitted from the light emitting unit 2 is applied to and transmitted through a finger 7 to be measured, which is fixed to receive light at a predetermined portion just below the light emitting unit 2. In the irradiation part of the finger 7 to be measured, the absorption and scattering of light by tissues other than blood and the venous blood layer are always constant with respect to a certain amount of incident light, and it depends on the change in thickness due to the pulsation of the arterial blood layer. The change in transmitted light can be selectively measured.

The filters 3A, 3B and 3C very sharply filter the light having the center wavelengths of 660 nm, 805 nm and 940 nm, and the photodiodes 4A, 4B and 3B arranged below these filters 3A, 3B and 3C. The 4C surely receives the transmitted light of each wavelength, and inputs the detection signal corresponding to the amount of the transmitted light to the pulse oximeter main body 10 through the lead wire 5.

Inside the pulse oximeter body 10, first, selective measurement of arterial blood at each wavelength is performed based on the pulsatile component (transmissive minimum value) and the non-pulsatile component (transmissivity maximum value) at each wavelength. Then, the absorbance (d ₁ , d ₂ and d ₃ ) at each wavelength is determined.

Oxyhemoglobin (HbO) to be obtained next₂), Reduced hemoglobin (RHb) and carbon monoxide hemoglobin (HbCO), respectively, as x, y and z, and three kinds of sample HbO as shown in FIG.₂, RHb and HbCO at three wavelengths 660, 805 and 940 nm, a₁b₁c₁, A ₂ b₂c₂, A₃b₃c₃With x as a coefficient, x, y and z can be obtained from the simultaneous equations of the three-dimensional first order.

The result is displayed as 100 × {HbO ₂ / (HbO ₂ + RHb + HbCO)} as SpO ₂ (%) on the pulse oximeter main body 10 and is continuously and continuously shown.

As described above, in the pulse oximeter of this example, the light emitting section 2 provided with the wide wavelength light source 2a is arranged above the fingertip, and the three types of filters 3A, 3B and 3C are arranged below the fingertip. The photodiodes 4A, 4B and 4C are arranged under these filters 3A, 3B and 3C, and the detection signals of the transmitted light of three kinds of wavelengths are supplied to the pulse oximeter main body 10, a conventional _{100 × {HbO 2 / (HbO} 2 + RHb)} and to SpO had asked ₂ (%), and enable the determination of the _{100 × {HbO 2 / (HbO} 2 + RHb + H bCO)}, conventional smokers Inaccurate SpO ₂ obtained from patients, etc. who have HbCO in their blood can be analyzed more accurately.

Although the above-mentioned embodiment has shown transmitted light of three kinds of wavelengths, a total of four filters 3D for passing a wavelength of 750 nm or 850 nm are added, and a photodiode 4D is further provided below it. The number of methemoglobin (MetHb) that absorbs more red light than carbon monoxide hemoglobin (HbCO) was calculated by adding the four photodiodes as the light receiving part, and the four hemoglobins were used as total hemoglobin. It is also possible to obtain a more accurate SpO ₂ of.

Further, although a plurality of filters are provided in parallel in the above-described embodiment, a plurality of filters may be mechanically switched instead of this. In this case, it is possible to configure a light receiving section consisting of one photodiode, and it is possible to make a more compact finger ox mounting device for a pulse oximeter.

Further, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the gist of the present invention.

[0033]

[Effect of device]

According to the present invention, a wide-wavelength light source is used for the light emitting unit, the transmitted light from the finger to be measured is divided by a plurality of filters, and the pulse oximeter that obtains the detection signal of the transmitted light of each wavelength from each photodiode is used. Not only oxyhemoglobin (HbO ₂ ) and reduced hemoglobin (RHb), but also amounts of carbon monoxide hemoglobin (HbCO) and methemoglobin (MetHb) can be measured, and arterial blood oxygen saturation (SpO ₂ ) can be determined more accurately. The effect is that you can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a pulse oximeter of the present invention.

FIG. 2 is a characteristic curve diagram showing the absorbance characteristics of oxyhemoglobin, reduced hemoglobin, and carbon monoxide hemoglobin.

FIG. 3 is a configuration diagram showing a conventional pulse oximeter.

[Explanation of symbols]

 1 Fingertip mounting device for pulse oximeter 2 Light emitting part 2a Wide wavelength light source 3A, 3B, 3C Filter 4A, 4B, 4C Photodiode 5,6 Lead wire 7 Finger to be measured 8 Finger insertion part 9A Shading member 10 Pulse oximeter body

Claims (1)

[Scope of utility model registration request] 1. A light emitting part having a wide wavelength light source, a light receiving part for receiving light from the light emitting part, and a finger insertion part provided between the light emitting part and the light receiving part. Is supplied to the light receiving section through a plurality of filters.