JP3115374B2 - Patient monitoring system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a patient monitoring system useful for grasping the oxygen supply / demand balance and circulatory dynamics of a patient in an operating room, an ICU or the like in a medical facility such as a hospital.

[0002]

2. Description of the Related Art Conventionally, an indicator dilution method has been used to measure cardiac output by a right heart catheterization method for a cardiac function test. In this indicator dilution method, the cardiac output is measured by heat diffusion. There are a thermodilution method and a dye dilution method for obtaining a cardiac output from a change in illuminance due to dye diffusion. In recent years, a cardiac output measurement device capable of continuously measuring cardiac output from a cardiac output obtained by a thermodilution method and a continuous blood flow velocity obtained by a thermal flow measurement (for example, JP-A-61-125329
Publications).

In addition, oxygen saturation monitors utilizing the absorption (reflection) characteristics of blood have become widespread, and there is also an apparatus for measuring mixed venous oxygen saturation (SvO ₂ ) incorporating an optical fiber in a right heart catheter. Is being developed.

[0004]

The cardiac output is a useful parameter in the evaluation of cardiac function. However, it alone determines the balance of circulation, respiration and metabolism, in other words, the overall balance of oxygen supply and demand. It is not possible. On the other hand, the mixed venous oxygen saturation value is a cardiac output which is an index of circulation, an arterial oxygen saturation which is an index of respiration,
It is a complex parameter that is influenced by any of oxygen consumption, which is an indicator of metabolism, and it is considered that it is difficult to grasp the patient's condition only by its value.

The present invention has been made in view of the above conventional example, and has as its object to provide a patient monitoring system that can more reliably grasp the supply and demand balance of oxygen and is useful for intraoperative and postoperative patient management. .

[0006]

In order to achieve the above object, a patient monitoring system according to the present invention comprises: an oxygen saturation measuring means for continuously measuring the oxygen saturation value of mixed venous blood; Cardiac output measuring means for measuring the output, parameter input means for inputting arterial blood oxygen saturation value and hemoglobin concentration, and the oxygen saturation value of mixed venous blood obtained by the oxygen saturation measuring means Oxygen for continuously calculating oxygen consumption from the cardiac output value obtained by the cardiac output measuring means, and the arterial oxygen saturation value and hemoglobin concentration input by the parameter input means. A consumption calculating means. Further, the oxygen uptake for continuously calculating the oxygen uptake rate from the oxygen saturation value of the mixed venous blood obtained by the oxygen saturation measuring means and the arterial blood oxygen saturation value inputted by the parameter input means. It has a rate calculating means.

Here, the oxygen saturation measuring means continuously measures the oxygen saturation of the blood based on the ratio of the intensity of the reflected light with respect to the irradiation of the blood with light of two different wavelengths. The cardiac output measuring means continuously calculates the cardiac output from the blood temperature and the equilibrium temperature at the time of measurement, based on the blood temperature at the time of calibration, the equilibrium temperature, and the cardiac output obtained by the thermodilution method. Measure.

[0008] Further, a single probe is provided for detecting and supplying necessary signals to the oxygen saturation measuring means and the cardiac output measuring means.

[0009]

In the above configuration, the continuously measured cardiac output and the mixed venous oxygen saturation value, and the hemoglobin concentration and the arterial oxygen saturation value input to the apparatus at the start of monitoring or periodically or continuously. , The oxygen consumption and the oxygen uptake rate are calculated, and are combined with the cardiac output and the mixed venous oxygen saturation value to continuously monitor the oxygen consumption and the oxygen uptake rate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment according to the present invention will be described below in detail with reference to the accompanying drawings. <System Configuration> FIG. 1 shows a patient monitoring system 1 of the present embodiment.
FIG. 3 is a block diagram showing the configuration of FIG. The patient monitoring system 1 of the present embodiment basically includes an oxygen consumption calculating unit 10 for calculating oxygen consumption, a cardiac output monitoring unit 20 for calculating cardiac output (hereinafter also referred to as CCOM), Oxygen saturation (hereinafter C
Oxygen saturation monitor 30 for calculating OSM)
, A power supply unit 40, and a probe 50.

An oxygen consumption calculator 10 includes a main CPU circuit 11 for controlling the entire system, and a main CPU circuit 1
1 for storing a control procedure, a RAM 13 for auxiliary storage including a hemoglobin concentration storage unit 13a and an arterial oxygen saturation storage unit 13b, and an operation key for inputting system operation keys or hemoglobin concentration and arterial blood oxygen saturation. 14, a display unit 15 for displaying monitoring information and the like,
D / A that realizes analog output of data outside the system
It has a conversion and analog output section 16 and a digital output section 17 such as RS-232C for realizing digital output to the outside of the system.

As will be described later in detail, the cardiac output monitoring unit 20 is basically composed of a CCOM measuring unit 21 for input processing of necessary data from a probe installed on a human body and a CCO measuring unit 21.
A CCOM operation unit 22 for calculating the cardiac output based on the data from the M measurement unit 21.

As will be described later in detail, the oxygen saturation monitoring unit 30 basically includes a COSM measuring unit 31 and a COSM measuring unit 31 for inputting necessary data from a probe installed on a human body.
A COSM operation unit 22 that calculates oxygen saturation based on data from the SM measurement unit 31.

A power supply section 40 is a line filter 41 for attenuating power supply noise from a commercial power supply, and a switching / supplying section for creating various power supplies in the system and supplying the power supplies to the respective sections.
The power supply circuit 42 has a regulator.

The probe 50 is a single probe, as shown in detail in FIG. 5, and can collect all the data required for the system.

In this system, the clocks are independent so that each control unit operates independently and asynchronously.
All controls may be synchronized with the clock from the PU circuit 11.

<Operation Procedure> FIG.
5 is a flowchart showing a control procedure of the first embodiment.

First, in step S21, whether a numerical value (hemoglobin concentration or arterial oxygen saturation) is input or not, in step S25, oxygen consumption (and / or oxygen intake rate).
It is determined whether or not the monitor display is performed. If neither of the processes is performed, the process loops steps S21 and S25.

In the case of a numerical value input, it is determined in step S22 which value is to be input. In the case of a hemoglobin concentration, the input value is determined in step S23 in the hemoglobin concentration storage unit 13a.
In the case of the arterial blood oxygen saturation, it is stored in the arterial blood oxygen saturation storage unit 13b in step S24.

On the other hand, in the case of the monitor display of the oxygen consumption,
Proceeding to step S26, the mixed venous blood oxygen saturation is received from the oxygen saturation monitor 30, and the cardiac output is received from the cardiac output monitor 40 in step S27. Step S
Mixed venous oxygen saturation and cardiac output received at 28;
The oxygen consumption is calculated from the hemoglobin concentration and the arterial oxygen saturation previously input and stored.

Here, a method of calculating the oxygen consumption will be described. As shown below, oxygen consumption (VO ₂ ), arterial blood oxygen content (CaC ₂ ), mixed venous blood oxygen content (Cv
O ₂ ) and the cardiac output (CO) include the Fick equation.

VO ₂ = (CaO ₂ −CvO ₂ ) × CO (1) On the other hand, the oxygen content is represented by the following formula, hemoglobin concentration (Hb), oxygen saturation (SxO ₂ ), and oxygen partial pressure (P
xO ₂ ) (where x is a to z), CaO ₂ = 1.34 × Hb × SaO ₂ + 0.0031 × PaO ₂ ... [2] CvO ₂ = 1.34 × Hb × SvO ₂ + 0.0031 × PvO ₂ [3] Since the second term of the equations [2] and [3] is extremely small and can be ignored, the equation [1] is as follows.

VO ₂ = 1.34 × Hb × (SaO ₂ −SvO ₂ ) × CO [4] From equation [4], the oxygen consumption (VO ₂ ) is represented by the hemoglobin concentration (Hb) and the arterial oxygen saturation. (SaO ₂ ), mixed venous oxygen saturation (SvO ₂ ), and cardiac output (CO). Obviously, if the oxygen consumption can be calculated, the oxygen uptake rate can also be calculated.

In step S29, the oxygen uptake rate below the oxygen consumption or the measured mixed venous oxygen saturation, cardiac output, etc. are subjected to format processing as necessary and displayed on the display unit 15.

<Example of Configuration of Cardiac Output Monitor> FIG. 3 is a block diagram of an example of the configuration of the cardiac output monitor.

In FIG. 3, reference numeral 20 denotes a main body of a cardiac output monitor section, to which externally exchangeable cardiac output measuring catheters 102 and 107 are connected. Catheter 102
Is a catheter for injecting an indicator and detecting an indicator temperature based on a thermodilution method, and comprises a temperature-sensitive element 103 for detecting the indicator temperature and a correction resistor 104 for correcting variations in the characteristics of the temperature-sensitive element. An indicator temperature probe circuit 115 is provided. The indicator temperature detection probe circuit 115 is connected to the infusion liquid temperature measurement circuit 124 of the measurement unit 21 of the cardiac output monitor unit via connectors 105 and 106.
And is located in the right atrium of the heart when measuring cardiac output.

The catheter 107 detects the temperature of the blood, and is heated by a constant current from the constant current source circuit 123 and cooled by the blood flow (hereinafter referred to as an equilibrium temperature). ) Is a catheter for detecting blood temperature and equilibrium temperature, and comprises a thermistor 108 for detecting the temperature of blood thermally diluted in the right atrium and right ventricle, and a correction resistor 109 for correcting the characteristics of the thermistor. Blood temperature probe circuit 116 and thermistor 110 for detecting a change in blood flow velocity as an equilibrium temperature by a thermal flow measurement method
An equilibrium temperature detection probe circuit 117 composed of (preferably a self-heating thermistor) is provided.

The blood temperature probe circuit 116 and the equilibrium temperature probe circuit 117 include connectors 111 and 112, respectively.
Via the measuring unit 21 of the main body of the cardiac output monitor unit
Is electrically connected to the blood temperature measurement circuit 125 and the equilibrium temperature measurement circuit 126, and is located in the pulmonary artery at the time of cardiac output measurement, and detects the central body temperature as a blood temperature signal.

Next, the operation of the cardiac output monitor will be described.

The cardiac output monitor 20 is divided as follows in terms of functions. That is, catheters 102 and 10
7, a measurement unit 21 that executes various temperature measurements, an opto-isolation communication circuit 135 that transmits measurement data and the like measured by the measurement unit 21 by optical means, and an opto-isolation communication circuit 135. A main CPU unit 22 for calculating and outputting the cardiac output intermittently by thermodilution method based on the input measurement data or continuously by equilibrium temperature measurement, and a heart calculated by the main CPU unit 22 An external output circuit 15 for outputting a stroke volume value to the outside
It is divided into 1.

In the measuring section 21, the infusate temperature measuring circuit 124 detects the temperature of the indicator discharged from the opening of the catheter 102 into the right atrium, and outputs a voltage signal corresponding to the detected temperature. The blood temperature measurement circuit 125 detects the blood temperature in the pulmonary artery and outputs a corresponding voltage signal,
The equilibrium temperature measuring circuit 126 detects the equilibrium temperature from the relation between the amount of heat applied to the self-heating type thermistor and the amount of heat taken off by the flow rate of the surrounding blood, and outputs a corresponding voltage signal.

The main CPU 144 is the local CPU 13
0, a signal for instructing each of the measuring circuits (the infusate temperature measuring circuit 124, the blood temperature measuring circuit 125, and the equilibrium temperature measuring circuit 126) to execute the measurement according to the program stored in the ROM 145, and controlling the measurement operation. Send. RAM
146 temporarily stores data necessary for control. These signals are transmitted via an opto-isolation communication circuit in a transmission format described later. Also, local C
The PU 130 sends a selection signal to the analog switch 127 to select the measurement data from each of the measurement circuits.
As a result, the measurement data from each measurement circuit reaches the A / D converter 128 via the analog switch, where it is converted into digital data and then taken into the local CPU 130. Then, the local CPU 130
In accordance with the program stored in 9, the received data is sent to the opto-isolation communication circuit 135 as serial data by its own serial communication function.

Opto-isolation communication circuit 135
Performs transmission and reception of data between the measurement unit 21 and the main CPU unit 22 in a state of being completely electrically insulated.
The optical transmission / reception circuits 136 and 137 each composed of a photodiode circuit and a phototransistor circuit, and the optical fiber glass 138 which electrically insulates the optical transmission / reception circuits from each other and serves as a signal transmission medium between them. Be composed. Therefore, the electrical connection between the voltage signal of the measuring section 20 and the voltage signal of the main CPU section 22 is completely cut off, and no closed loop is formed between the human body and the main CPU side. Can be done.

Next, the operation of the main CPU section 22 will be described. Serial data from the opto-isolation communication circuit 135 is received by the main CPU 144. In a case where the cardiac output is calibrated by the thermodilution method, the cardiac output calibrating means 141 measures the temperature of blood caused by the injection of a cooled or warmed infusate. From the blood temperature measurement circuit 125 for measuring a change, a signal relating to the thermodiluted blood temperature is received from the main CPU 144. At the same time, the cardiac output calibrating means 141 calculates the thermodiluted cardiac output from the infusate temperature, the infusate specific heat, the infusate specific gravity, the blood specific gravity, the blood specific heat, and the thermodiluted blood temperature based on the Stuart-Hamilton equation. And outputs the result to the calibration signal storage means 142 as a calibration cardiac output signal. In addition, when the injection of the indicator by the thermodilution method cannot be performed in a serious patient, the corresponding cardiac output is set by a setting switch such as a thumbwheel switch or a digital switch, and a cardiac output input means 150 including a keyboard. Is input and output to the calibration signal storage means 142 as the cardiac output value at the time of calibration.

The calibration signal storage means 142 stores the cardiac output value by the thermodilution method or the cardiac output input means 150.
Is stored as the cardiac output during calibration, and the blood temperature signal from the blood temperature measurement circuit 125 and the equilibrium temperature signal from the equilibrium temperature measurement circuit 126 are respectively calibrated. The blood temperature and the equilibrium temperature during calibration are retained and stored. Then, when there is a request from the continuous cardiac output calculation means 143, the stored data is output.

The continuous cardiac output calculating means 143 calculates the cardiac output at the time of calibration, the blood temperature at the time of calibration, the equilibrium temperature at the time of calibration, and the blood temperature at the time of measurement, which are stored and held by the signal storage means 142 at the time of calibration. Based on the equilibrium temperature at the time of measurement, the continuous cardiac output is calculated based on the following equation [5].

CO = CO _CAL × ((Tt _R− K · (TB−TB _CAL )) / Tt _CAL ) ^{1 / A} (5) where CO: cardiac output, CO _CAL : heart at the time of calibration Output T
t _R : equilibrium temperature at measurement, TB: blood temperature TB _CAL : blood temperature at calibration, K: temperature correction constant Tt _CAL : equilibrium temperature at calibration, A: constant.

From the above equation [5], it can be seen that the correction of the equilibrium temperature change accompanying the blood temperature change from the time of calibration is also performed. Therefore, it is possible to continuously measure the cardiac output with high accuracy without measuring the absolute value of the blood flow velocity.

In the above configuration, the body temperature (blood temperature in the pulmonary artery) at the central part at the time of measurement and calibration, the equilibrium temperature at the time of heating and cooling by the blood flow to reach an equilibrium state, and the heart rate The output is obtained, the change in blood flow velocity is detected as a temperature change, the change in cardiac output is directly obtained from the temperature change information, and it is calculated experimentally using functions and parameters that match the probe output. In addition, the cardiac output can be continuously measured without measuring the absolute value of the blood flow velocity.

<Example of the Configuration of the Oxygen Saturation Monitor> FIG. 4 is a block diagram showing an example of the configuration of the oxygen saturation monitor.

In the figure, reference numeral 211 denotes a catheter which is indwelled in a pulmonary artery or the like and measures the reflected light intensity of light in blood. A pulse timing circuit 212 outputs a drive timing signal of the LEDs 214 (241 and 242) to the LED drive circuit 213, and outputs a timing signal for sampling the intensity of reflected light from light of different wavelengths emitted from each LED. Sample and hold circuit 21
8 is output. Reference numeral 213 denotes an LED driving circuit, which is driven by a timing signal from the pulse timing
One of the two LEDs 241 and 242 of the ED 214 is driven to emit light. Reference numeral 214 denotes a light-emitting diode (LED) capable of outputting light having a wavelength of 660 nm and light having a wavelength of 805 nm. In this example, the light-emitting diode 214 includes an LED 241 (having a wavelength of 660 nm) and an LED 242 (having a wavelength of 805 nm). . In this manner, the light of different wavelengths emitted from each LED is combined by an optical coupler, collected into one optical fiber, and sent to the catheter 211.

The wavelength of the output light of the LED 214 is changed to 660 n by changing the drive voltage or the like.
Assuming that the LED can be changed between m and 805 nm, 1
One LED can be substituted.

A connection portion 215 connects the catheter 211 and the oxygen saturation monitor main body, and the catheter 211 and the main body are connected by an optical cable 228. Reference numeral 216 denotes a portion where the photoelectric conversion unit and the preamplifier are integrated, and inputs reflected light from the catheter 211 and outputs an electric signal corresponding to the intensity of the input light. A main amplifier 217 further amplifies the electric signal from the photoelectric conversion unit 216. The sample hold circuit 218 receives the timing signal from the pulse timing circuit 212, and samples and holds the analog signal from the main amplifier 217 in synchronization with the timing signal.

Since the light of each wavelength emitted from the LED 214 is controlled by the timing signal from the pulse timing circuit 212 so as not to overlap with each other in time, the sample and hold circuit 218 reflects the light for each wavelength. Light intensity can be held independently. The signal thus sampled and held is output to the control unit 32 after the noise component is filtered by the filter circuit 219.

In the control section 32, the analog signal from the filter circuit 219 is converted into a digital signal by the A / D converter 222 and input to the CPU circuit 221. The control unit 32 receives the timing signals 233 and 234 from the pulse timing circuit 212, and
It is possible to determine which one of the digital signals input from the D converter 222 has the reflected light intensity for which wavelength. Here, for example, the timing signal 23
3 indicates the input timing of the reflected light intensity for the light having the wavelength of 660 nm, and the timing signal 234 indicates the wavelength 805n.
The input timing of the reflected light intensity for the light of m is shown.

Reference numeral 221 denotes a C including a microprocessor or the like.
The PU circuit controls according to a control program and various data stored in the ROM 224. A RAM 225 is used as a work area of the CPU circuit and temporarily stores various data. An external output circuit 228 outputs, for example, measurement data to an external device connected through an external output terminal.

When the difference between the absorption characteristics of hemoglobin not bound to oxygen and the absorption characteristics of hemoglobin bound to oxygen increases, the difference between these two characteristics is “0”.
And the corresponding wavelength is 660n
m, 805 nm. Therefore, the blood is irradiated with each of these two wavelengths, the reflected light is detected, and the ratio between the two is obtained, whereby the oxygen saturation in the blood can be obtained.

<Example of Probe Configuration> FIG.
FIG. 3 is a diagram showing an example of the configuration of FIG. This probe includes the cardiac output measuring catheter 107 and the oxygen saturation monitoring catheter 211 as one unit. The probe reflects light incident on the optical fiber for light irradiation or reflected in blood. It integrates an optical fiber for light incidence for taking in. The probe 50 is inserted into, for example, a pulmonary artery or the like, and continuously measures cardiac output and blood oxygen saturation.

[0049]

According to the present invention, it is possible to provide a patient monitoring system which can more reliably grasp the supply and demand balance of oxygen and is useful for intraoperative and postoperative patient management.

That is, the oxygen saturation value and the cardiac output can be continuously monitored with a single probe. Further, the oxygen consumption can be continuously calculated from the continuous information of the mixed venous oxygen saturation (SvO ₂ ) and the cardiac output, and the input information of the hemoglobin concentration and the arterial oxygen saturation. Further, by continuously inputting the arterial blood oxygen saturation from a pulse oximeter or the like, the oxygen consumption can be monitored more accurately and the oxygen intake rate can be calculated.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a patient monitoring system according to an embodiment.

FIG. 2 is a flowchart showing a control procedure of a main CPU circuit.

FIG. 3 is a block diagram of a configuration example of a cardiac output monitor section.

FIG. 4 is a block diagram showing one configuration example of an oxygen saturation monitor.

FIG. 5 is a diagram showing a configuration example of a probe.

[Description of sign]

10: oxygen consumption calculation unit, 20: cardiac output monitor unit, 3
0: oxygen saturation monitoring section, 40: power supply section, 50: probe

Continuation of the front page (56) References JP-A-2-134132 (JP, A) JP-A-2-111343 (JP, A) JP-A-2-13450 (JP, A) JP-A 64-11531 (JP) , A) JP-A-1-146524 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 5/145 A61B 5/00 102 A61B 5/0205

Claims (5)

(57) [Claims] 1. An oxygen saturation measuring means for continuously measuring the oxygen saturation value of mixed venous blood, a cardiac output measuring means for continuously measuring cardiac output, and an arterial oxygen saturation value. Parameter input means for inputting the hemoglobin concentration, the oxygen saturation value of the mixed venous blood determined by the oxygen saturation measurement means, and the cardiac output value determined by the cardiac output measurement means An oxygen consumption calculating means for continuously calculating oxygen consumption from the arterial blood oxygen saturation value and the hemoglobin concentration input by the parameter input means. 2. An oxygen uptake rate is continuously calculated from the oxygen saturation value of the mixed venous blood obtained by the oxygen saturation measurement means and the arterial blood oxygen saturation value inputted by the parameter input means. 2. The patient monitoring system according to claim 1, further comprising: an oxygen intake rate calculating unit that performs the calculation. 3. The oxygen saturation measuring means according to claim 1, wherein the oxygen saturation measuring means continuously measures the oxygen saturation of the blood based on the ratio of the intensity of the reflected light with respect to the irradiation of the blood with light of two different wavelengths. A patient monitoring system as described. 4. The cardiac output measuring means includes a blood temperature at the time of calibration,
To continuously measure the cardiac output from the blood temperature at the time of measurement and the equilibrium temperature depending on the blood flow rate, based on the equilibrium temperature depending on the blood flow rate and the cardiac output determined by the thermodilution method The patient monitoring system according to claim 1, wherein: 5. The patient monitoring system according to claim 1, further comprising a single probe for detecting and supplying signals required for said oxygen saturation measuring means and said cardiac output measuring means. .