JP7081075B2 - Monitor system control method, monitor system and program - Google Patents

Description

The present disclosure relates to control methods, monitor systems and programs for monitor systems.

Conventionally, there has been known a technique for deriving VCO2 or the like, which is the amount of CO2 excreted once, from a volume capnogram analysis method for one breath (see, for example, Patent Document 1 and Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-061071

Hirabayashi G, Tsukakoshi S, Andoh T, More. Effect of pressure-controlled radio ventilation on dead space daring robot-assisted laparoscopic radical prostate EJA. 35 (4): 307-314, April 2018

By the way, functional residual volume FRC (Functional Residental Capacity), which is one of the lung volume fractions by respiratory physiology, is a basic concept that supports the gas exchange function (O2 intake / CO2 excretion) of the lungs.

By adding the next inspiratory volume VTI to the functional residual gas volume FRC, which is the amount of gas remaining in the lungs at the end of exhalation, the pressure difference between the alveolar gas and lung capillary blood expands and gas exchange occurs. .. As a result, the oxygen amount VO2 is ingested into the blood, and the CO2 single excretion amount VCO2 is excreted into the exhaled breath.

FRC abnormalities are a major risk factor for gas exchange normality. In particular, in patients with artificial respiration management such as during surgical anesthesia and intensive care, the FRC is likely to decrease due to the development of atelectasis, and the risk of leading to hypercapnia and hypoxemia increases.

Therefore, it is an object of the present disclosure to make FRC monitoring feasible.

According to one aspect of the present disclosure, a flow sensor that continuously detects the flow of a patient's breathing gas, a breathing gas sensor that continuously detects the concentration of a component gas of the breathing gas, the flow sensor, and the breathing gas sensor. A control method for a monitor system equipped with a control device connected to the
The control device relates to a single breath.
The concentration / partial pressure in two-dimensional coordinates is synchronized with V, which is the ventilation volume based on the measurement result of the flow sensor, and FCO2 or PCO2, which is the concentration or partial pressure of CO2 gas based on the measurement result of the breathing gas sensor. -Create a ventilation loop,
Obtained as VCO2, which is the amount of CO2 gas excreted, based on the area surrounded by the concentration / partial pressure-ventilation volume loop.
Using the VCO2, an inverse proportional curve including the relationship of V = VCO2 / FCO2 or V∝VCO2 / PCO2 is generated.
Based on the concentration / partial pressure-ventilation volume loop and the inverse proportional curve, the FRC, which is the functional residual air volume, is calculated.
A method for controlling a monitor system that outputs the calculated FRC is provided.

According to the present disclosure, FRC monitoring becomes feasible.

It is explanatory drawing of the monitor system which concerns on one Embodiment. It is a figure which shows an example of the hardware composition of a control device. It is explanatory drawing of a volume capnogram and the like. It is a figure which shows the example of a volume capnogram. It is a figure which shows the volume capnogram used in this embodiment. It is explanatory drawing of the volume capnogram which is the premise of the calculation of the functional residual air amount FRC. It is explanatory drawing of the alveolar air CO2 concentration change in FRC and the diffusion inflow of VCO2. It is a figure which shows the model of the respiratory fluctuation of the alveolar air CO2 partial pressure, and the diffusion flow / diffusion amount of CO2. It is explanatory drawing of another example of the calculation method of the functional residual air amount FRC. It is a figure (the 1) which shows the example of FRC calculation during general anesthesia of pneumoperitoneum. It is a figure (No. 2) which shows the example of FRC calculation during general anesthesia of pneumoperitoneum. It is a figure (3) which shows the example of FRC calculation during general anesthesia of pneumoperitoneum. It is a flowchart which shows the operation example for FRC calculation processing realized by the control device. It is a flowchart which shows an example of the FRC calculation process (step S116 of FIG. 11).

Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. The notation such as "CO ₂ " is not the notation "CO ₂ " using subscripts, but has the same meaning as the notation "CO 2".

FIG. 1 is a diagram illustrating a case where the monitor system 200 according to one embodiment is applied to an inhalation anesthesia system 100 having a circulating breathing circuit. The monitor system 200 is a monitor system based on the volume capnogram analysis method. The volume capnogram analysis method plots the ventilation volume and CO2 concentration (partial pressure) obtained from the flow sensor installed at the mouth and the mainstream CO2 sensor on the XY coordinate plane, respectively, as explained below. It is an analysis method that analyzes the drawn volume capnogram (see the thick line in FIG. 6 below) according to a certain rule in terms of CO2 excretion ability.

As shown in FIG. 1, the monitor system 200 includes a control device 3, a flow sensor 13, and a respiratory gas sensor 14.

The inhalation anesthesia system 100 includes a circulating breathing circuit 1, a gas supply device 2, and a ventilator 17. The breathing circuit 1 includes an intake valve 11, a connector 12 connected to the patient, an exhalation valve 15, and a CO2 absorbent canister 16. The intake valve 11 operates so as to allow the flow of gas (intake) from the breathing circuit 1 to the patient, but regulate the reverse flow. The exhalation valve 15 operates to allow gas flow (exhalation) from the patient to the anesthesia system, but regulate the reverse flow. A part of the exhaled breath is guided to the CO2 absorber canister 16 and reused, and the remaining part is discarded as a surplus gas. The CO2 absorber canister 16 is for absorbing and removing carbon dioxide from the exhaled breath of a patient and circulating other anesthetic breathing gas, O2 gas, etc. as a part of inspiration.

A flow sensor 13 and a breathing gas sensor 14 are installed in series on the connector 12 in no particular order. The flow sensor 13 detects a change in the flow rate on the time axis of respiration, integrates it, and measures the tidal volume (VTI, VTE). The breathing gas sensor 14 is composed of, for example, a mainstream type breathing gas sensor, but is a sidestream type that samples sample gas from the 14 positions by a suction pump and a sensor body incorporated in a remote place, for example, a control device. You can also use the breathing gas sensor. The change in the concentration of the component gas of the respiratory gas on the time axis is detected, and the inspiratory concentration and the expiratory terminal concentration are measured from there. Here, the flow sensor 13 and the breathing gas sensor 14 measure an anesthetic breathing gas in which oxygen (O2), volatile anesthetic gas (AA), and nitric oxide (N2O) are mixed in addition to carbon dioxide (CO2). Can be done. When adjusting the concentration of O2 or when supplying and adjusting the anesthetic gas of AA and N2O, the gas supply device 2 is used. The ventilator 17 is used to replace or assist the patient's breathing.

FIG. 2 shows the connection relationship between the flow sensor 13 and the mainstream respiratory gas sensor 14 and the control device 3. The signals detected by the flow sensor 13 and the breathing gas sensor 14 are supplied to the control device 3 by the passing breathing gas.

The control device 3 includes a storage device 31, an arithmetic unit 32, an input device 33, and a display device 34.

The flow sensor circuit 36 and the breathing gas sensor drive circuit 37 are connected to the calculation device 32 via the interface (I / F) 35, and the calculation device 32 acquires a signal from the flow sensor 13 and the breathing gas sensor drive circuit 37. The breathing gas sensor 14 is controlled via the sensor 14 to acquire a signal, and the calculation necessary for processing these signal data is performed. The storage device 31 connected to the arithmetic unit 32 includes means including a breathing gas sensor drive procedure storage means, a signal data storage means, a program storage means, a calculation procedure storage means, and the like, which are necessary for various calculations performed by the arithmetic unit 32. Is stored.

The hardware configuration of the control device 3 shown in FIG. 2 is a hardware configuration of a Neumann computer including a storage device 31, an arithmetic unit 32, an input device 33, and a display device 34. A main storage device or an auxiliary storage device of a Von Neumann computer can be used for data storage and program storage. A volatile DRAM is often used as the main storage device, and a magnetic disk such as a hard disk (HD), a magnetic tape, an optical disk, a magneto-optical disk, a RAM disk, a USB flash memory, or the like can be used as the auxiliary storage device. .. A part of the calculation performed by the arithmetic unit 32 can also be realized as a hardware configuration by another arithmetic unit (CPU) or another computer system. Further, the arithmetic unit 32 is connected to an input device 33 such as a touch panel, a keyboard and a mouse, and a display device 34 such as a printer and a display. The control device 3 is not provided with the display device 34, and the display device 34 may be provided so as to be connected to the control device 3. Further, some or all the functions of the control device 3 may be realized by an external server device (not shown).

As the gas analysis method, it is preferable to use a mainstream gas analysis method capable of continuously monitoring the respiratory gas concentration such as CO2 / O2 / N2O / AA at the patient's mouth. In the conventional sidestream gas analysis method, which is the mainstream in the clinical field, inspiratory gas and exhaled gas are continuously sampled at around 100 mL / min from the mouth, detected by a sensor at a remote location, and the concentration change on the time axis and inspiration. Concentration / end exhalation concentration is measured and displayed. For this reason, it was difficult to handle it integrally with the ventilation volume data due to the delay in the reaction to the concentration change due to mixing during sampling. However, since high-speed sidestream type respiratory gas sensors that can analyze with a smaller sampling flow rate have appeared in recent years, they are not necessarily limited to the mainstream type.

FIG. 3 is a diagram showing a volume capnogram and a predetermined inverse proportional curve (described later) on XY coordinates with the partial pressure P as the X axis and the ventilation volume V as the Y axis.

There are two methods for expressing how much a specific gas is contained in the respiratory gas: partial pressure and concentration. Both are proportional under the same temperature and pressure. In the living body, in order to facilitate comparison with blood, it is usually expressed as a partial pressure at body temperature, atmospheric pressure, and saturated water vapor pressure (BTPS). For example, when the body temperature is 37 ° C. and the atmospheric pressure is 760 mmHg, the saturated water vapor pressure is 47 mmHg. Therefore, in the case of CO2, there is a relationship of [partial pressure PCO2 = (760-47) × concentration FCO2]. Although the relationship of [ventilation volume V x concentration FCO2 = CO2 volume] is established, partial pressure PCO2 is sometimes used in graphs of clinical data and the like. As described above, the partial pressure and the concentration have a one-to-one correspondence with each other, and one is a parameter that can be replaced by the other. Hereinafter, k = (760-47) is set, and for convenience, k is also referred to as a “conversion constant”.

3 and 5 show the partial pressure-ventilation loop of CO2 in respiratory gas in one breath as a volume capnogram. In FIG. 6, which will be described later, as a volume capnogram, the concentration of CO2 in the respiratory gas in one breath-ventilation volume loop is shown.

In FIGS. 3 and 5, the predetermined inverse proportional curve is V = k × VCO2 / PCO2 + (VTI-VTE).

As shown by the arrow on the volume capnogram in FIG. 3, CO2 is normally not contained in the inspiratory, so that the volume capnogram rises on the Y-axis at the time of inspiration to obtain the one-time inspiratory amount VTI in the figure. Reach the point to represent. The air contains about 21% O2, but the O2 gas that enters the lungs from the airways during inspiration travels from the alveoli to the blood of its capillaries. This movement is called ingestion. On the other hand, CO2 generated in the tissue dissolves in venous blood, returns to the heart, passes through the pulmonary artery, and moves to the alveoli in the form of replacing oxygen in the capillaries of the alveoli. This movement is called excretion. When inspiration is replaced by exhalation in terms of the amount of one-time inspiration VTI, excretion of CO2 to the outside of the body begins, and as shown by the arrow on the volume capnogram in FIG. 3, exhaled breath corresponding to the CO2 concentration F in exhalation. The medium CO2 partial pressure P increases according to the exhalation amount, reaches the partial pressure PETCO2 corresponding to the exhalation terminal CO2 concentration FETCO2 in the figure, and ends one breath. By calculating the area surrounded by this volume capnogram, the CO2 single excretion amount (CO2 single call amount) VCO2 can be obtained. Specifically, in FIG. 3, since the horizontal axis is the partial pressure, assuming that the area surrounded by the volume capnogram is S, the conversion constant k is used and the relationship is VCO2 = S / k.

In the following description, the following relational expression (1) is used. C. Bohr proposed a relational expression known as the Bohr equation (see C. Bohr, "Uever die lunatumung", Scand Arch Physiology, vol.22, pp. 236-238, 1891). The following relational expression (the amount of CO2 in one exhaled breath is equal to the amount of CO2 in one alveolar ventilation) is based on the Bohr equation.

VTE x PECO2 = (VTE-VDressp) x PAmaxCO2 (1)

(In one equation, VTE represents the one-time expiratory volume, PECO2 represents the partial pressure corresponding to the mixed expiratory concentration, VDresp represents the respiratory dead space volume, and PAmaxCO2 represents the partial pressure corresponding to the maximum alveolar air CO2 concentration).

Here, VTE-VDresp represents alveolar ventilation VA, and VA means an ideal alveolar air space filled with a homogeneous maximum alveolar air CO2 concentration FAmaxCO2.

As shown in FIG. 5, the exhaled breath CO2 concentration that actually rises continuously according to the change in the exhalation volume is set to the mixed exhaled breath concentration, that is, the ventilation volume less than PECO2 with PECO2, which is a partial pressure corresponding to the expiratory average concentration, as a boundary. Alveolar ventilation filled with FAmaxCO2 corresponding to PAmaxCO2, where the alveoli are homogeneous by complete gas exchange, truncated as ineffective ventilation without gas exchange or respiratory dead space VDressp and after exceeding PECO2. Rounding up to VA, this is the concept of (1).

In order to obtain PAmaxCO2, VCO2 × k (CO2 single excretion amount × k) is first calculated from the volume capnogram (circled number 2 in FIG. 5).

Next, the left side VTE × PECO2 of (1) represents the area of a rectangle whose diagonal lines are a point (X = 0, Y = VTI-VTE) and a point (X = PECO2, Y = VTI). Since this area is the CO2 single excretion amount VCO2 × k, the vertical length × the horizontal length = (VTI- (VTI-VTE)) × (PECO2-0) = VTE × PECO2 = VCO2 × k. , PECO2 (partial pressure corresponding to the mixed exhaled breath concentration FECO2. Circled number 3 in FIG. 5) can be obtained.

When PECO2 is obtained, the Y coordinate of the point G on the volume capnogram is obtained, so that VA (= VTE-VDressp) can be obtained.

Next, the right side (VTE-VDresp) × PAmaxCO2 of the equation (1) is a rectangle having a point (X = 0, Y = VTI-VTE) and a point (X = PAmaxCO2, Y = VTI-VDresp) diagonally. Represents the area. Since this area is also VCO2 × k, the vertical length × the horizontal length = ((VTI-VDressp)-(VTI-VTE)) × (PAmaxCO2-0) = (VTE-VDressp) × PAmaxCO2 = VCO2. × k, and PAmaxCO2 (partial pressure corresponding to the maximum alveolar air CO2 concentration. Circled number 5 in FIG. 5) can be obtained. As described above, (VTE-VDresp) is equal to VA and can be derived based on the point G.

Next, the maximum point (H in FIG. 5) of the area of the rectangle inscribed in the volume capnogram is obtained, and the phase II and phase III branches of the expiratory phase of the volume capnogram are obtained by the Y coordinate of the maximum point. When the Equal Area method is applied to the phase II identified by the point and the I of FIG. 5 is obtained, the airway dead space amount VDaw (circled in FIG. 5) is obtained by VTI- (Y coordinate of the point I). The number 6) can be specified. Since the respiratory dead space VDresp has already been obtained, the alveolar dead space VDalv (circled number 7 in FIG. 5) can be specified by "respiratory dead space VDresp-airway dead space VDaw".

The Equal Area Method is a traditional method for analyzing exhaled CO2 gas, which is described in detail in the following literature, for example.
R. Fletcher, B. Johnson, G.M. Cumming and J. Brew, "THE CONCEPT OF DEADSPACE WITH SPECIAL REFERENCE TO THE SINGLE BREATH TEST FOR CARBON DIOXIDE", Br. J. Anast. , Vol. 53 (1), pp. 77-88, 1981
Conventionally, as shown in FIG. 4, the CO2 waveform of exhaled breath drawn with the ventilation volume on the X-axis and the CO2 concentration on the Y-axis is called a volume capnogram. Volume capnograms are usually divided into phase I, which is CO2-free, phase III, which represents alveolar air equilibrium with pulmonary capillary blood, and phase II, which represents the transition from phase I to phase III. It is divided into anatomical dead space volume VDanat (or airway dead space volume VDaw) and alveolar ventilation volume VA by a line that equalizes the two areas hatched in the middle of Phase II. It is customary.

As shown in FIG. 3, in the volume capnogram of the present embodiment, the X-axis and the Y-axis of the conventional volume capnogram shown in FIG. 4 are exchanged, and the CO2 concentration is on the X-axis and the ventilation volume is on the Y-axis. It is the one that took. There is no essential difference between the two.

In FIG. 5, the inspiratory air is exhaled after reaching VTI on the Y-axis. Phase I from the starting point of exhalation VTI to the rising point of CO2 concentration, and the second II from the rising point of CO2 concentration on the Y-axis to the point H where the rectangular area in contact with the CO2 calling line on the right shoulder is maximized. It is divided into a phase and a phase III from the point H to the point (PETCO2) indicating the exhaled CO2 concentration FETCO2. Phase I is complete dead space qi, phase II is transitional phase, and phase III is alveolar qi. In the present invention, the phase II and the phase III are separated at the point H where the rectangular area in contact with the right shoulder of the CO2 calling line is maximized, and then the Equal Area method is applied to the airway dead space amount VDaw ( The circled number 6) is specified. Alveolar dead space volume VDalv (circled number 7) = respiratory dead space volume VDresp (circled number 4) -from airway dead space volume VDaw (circled number 6) to alveolar dead space volume VDalv (circled number 7) Can be obtained.

In the monitor system 200 according to the present embodiment, the functional residual air amount FRC is further calculated based on the volume capnogram and the PV inverse proportional curve (or the VF inverse proportional curve of FIG. 6). The method for calculating the functional residual air volume FRC will be described in detail below. In another embodiment, the functional residual air volume FRC may be calculated without calculating the airway dead space volume VDaw or the alveolar dead space volume VDalv as described above.

When the control device 3 calculates the functional residual air amount FRC, the control device 3 outputs the calculated functional residual air amount FRC. The output method of the functional residual air amount FRC is arbitrary, and may be accompanied by output such as display and voice. Alternatively, the control device 3 may output the functional residual air amount FRC in a manner of outputting an alarm or the like when the functional residual air amount FRC falls below a predetermined threshold value.

However, for general monitoring applications, the control device 3 preferably displays the functional residual air amount FRC on the display device 34. For example, the control device 3 has the same XY coordinates of a volume capnogram, a rectangle representing a CO2 single excretion amount VCO2 (or VCO2 × k), and a surface positive large rectangle inscribed in the volume capnogram for each breath. CO2 gas excretion per breath VCO2, maximum alveolar air CO2 concentration FAmaxCO2 (or PAmaxCO2), expiratory terminal CO2 concentration FETCO2 (or PETCO2), mixed exhalation concentration FECO2 (or PECO2), The respiratory dead cavity volume VDresp, alveolar ventilation volume VA, airway dead cavity volume VDaw, alveolar dead cavity volume VDalv, and functional residual air volume FRC are displayed in a predetermined area of the display device 34. As described above, in other embodiments, the calculation and display of the airway dead space amount VDaw and the alveolar dead space amount VDalv may be omitted. In addition, the display of an area positively large rectangle inscribed in the volume capnogram may be omitted.

FIG. 6 is an explanatory diagram of a method for calculating the functional residual air amount FRC, and shows a graph similar to the graph shown in FIG. However, in FIG. 6, the horizontal axis is the concentration of CO2, and the origin of the vertical axis corresponds to the case of (VTI-VTE = 0) in the graph shown in FIG. The calculation of the functional residual air amount FRC can also be realized from the graph shown in FIG. 5, and such a difference is not essential. In the case of FIG. 6, the area sandwiched between the volume capnogram waveform and the horizontal axis (X-axis) represents VCO2, which is the amount of CO2 contained in the exhaled breath.

In FIG. 6, the abbreviations and their explanations are as follows.
VTE: Tidal volume (expiratory volume)
FCO2: CO2 concentration. The ratio of partial pressure PCO2 to the total pressure. Under the same temperature and pressure, the ratio of CO2 partial pressure to the total pressure excluding water vapor partial pressure.
VCO2: CO2 excretion amount once. The area within the volume capnogram (thick line), which is the integral value of ventilation volume x concentration.
VP1: Phase I amount. The part of the exhaled air from the airway in the early stage of exhalation that does not contain CO2.
VP2: Phase II amount. Transition phase from VP1 to VP3. The airway dead space volume VDaw is defined as the area from the start of the call to the middle of the area of VP2.
VP3: Phase III amount. Represents exhalation from the alveoli. Corresponds to the Y coordinate of point H.
Point G: The point where the X coordinate of the point on the volume capnogram (thick line) is FECO2. Area C = Area D. The area C and the area D are the areas of the regions hatched by the fine diagonal lines in FIG.
Point H: A point (X, Y) on the volume capnogram (thick line), and the maximum point of the product XY (FAminCO2, VP3).
VD (resp): (breathing) dead space volume. Ventilation volume from the start of the call to point G. Includes airway dead space VDaw and alveolar dead space VDalv (excluding shunt effect).
VA: Alveolar ventilation. It is defined by VA = VTE-VD, and VA = VCO2 / FAmaxCO2.
FECO2: Mixed exhaled breath concentration. Mixed average concentration of CO2 contained in one-time exhalation volume. FECO2 = VOC2 / VTE, which represents the amount of CO2 excreted per unit ventilation volume.
FETCO2: Instantaneous CO2 concentration of exhaled breath that reached the mouth at the end of exhalation (end of exhalation CO2 concentration).
FAmaxCO2: Maximum alveolar air CO2 concentration. It is a point on the X-axis where area A = area B, and represents the terminal alveolar air concentration at the end of exhalation. FAmaxCO2 = VCO2 / VA, which represents the amount of CO2 excreted per unit alveolar ventilation. It should be noted that the area A and the area B are the areas of the areas hatched by "stitches" in FIG.
FAminCO2: Minimum alveolar air CO2 concentration. Corresponds to the X coordinate of point H. Since it is the starting point of VP3, it represents the minimum alveolar air concentration at the end of inspiration.

Here, gas exchange in the lung is microscopically described as diffusion at the alveolar-capillary barrier. Diffusion flow rate = diffusion coefficient x area x pressure difference / distance [Fick's law], that is, the amount of diffusion per unit time is proportional to the area and the pressure difference and inversely proportional to the distance. In the case of human living lung, the area is 50 to 100 square meters, the distance (thickness) is about 0.3 micrometer, and the diffusion coefficient depends on the type of gas. Diffusion flow rate = DL × voltage division difference.

Since carbon dioxide is characterized by rapid movement between gas and liquid, and the partial pressure PCO2 and the concentration FCO2 are in a linear proportional relationship, it is suitable for describing gas exchange between gas and liquid. Under the same temperature and pressure, FCO2 = PCO2 / (Patm-PH2O), and under atmospheric pressure, body temperature 37 ° C., and saturated steam pressure, there is a relationship of FCO2 = PCO2 / k.

Fick's law, that is, the difference in pressure at diffusion flow rate = DL × difference in pressure, is caused by respiration. The carbon dioxide alveolar mood pressure PAmaxCO2, which was maximized at the end of exhalation in a state of almost equilibrium with the pulmonary capillary blood (≈PcCO2 (C represents the capillary capillary)), is minimized to PAminCO2 by the completion of the inflow of the next inspiratory volume VTI. To become. Then, a partial pressure difference PcCO2-PAminCO2 is generated between the blood and the capillary blood, and this serves as a driving force to diffuse carbon dioxide from the blood to the alveoli. The sum of this microscopic diffusion phenomenon is the amount of CO2 excreted per breath in the lungs as a respiratory organ, VCO2 (the amount of CO2 diffused from the blood to the alveoli and called).

Macroscopically, it can be said that VCO2 is produced by fluctuations in alveolar mood pressure (concentration) in the FRC space. If this concept is equationd as it is, FRC × (FAmaxCO2-FAminCO2) = VCO2, and the following equation is obtained.
FRC = VCO2 / (FAmaxCO2-FAminCO2) (2)

In equation (2), VCO2 is obtained from volume capnogram analysis, as described above. As PAmaxCO2, the exhaled terminal alveolar mood pressure (not the exhaled terminal mouth mood pressure) at which the diffusion from the pulmonary capillary blood to the alveoli ends is suitable. PAmaxCO2 is obtained from volume capnogram analysis as described above. As PAminCO2, the first called inspiratory terminal alveolar air, that is, the start point of the phase III (the end point of the phase II) is suitable. That is, as shown in FIG. 6, PAminCO2 is the concentration of CO2 gas corresponding to the maximum point H of the rectangle inscribed in the volume capnogram (see also the maximum point H in FIG. 5). Therefore, the functional residual air volume FRC can be derived from the volume capnogram analysis.

From the above, it can be seen that the functional residual air amount FRC defined by the macroscopic concept can be calculated by the equation (2). Since the right side of the equation (2) represents the amount of CO2 diffused per unit concentration difference (division pressure difference), it is the "CO2 diffusion functional residual air amount". Since it does not include a closed cavity without a diffusion function, it can be said to be a lung function evaluation method from the viewpoint of diffusion and excretion of CO2, not just a gas volume (see FIG. 7).

FIG. 7 is an explanatory diagram of changes in alveolar air CO2 concentration in the FRC and diffusion inflow of VCO2.

In FIG. 7, the abbreviations and their explanations are as follows.
PvCO2: Venous blood CO2 partial pressure PaCO2: Arterial blood CO2 partial pressure In FIG. 7, 700 is an alveolar model schematically representing the entire alveoli, and 702 schematically represents the capillaries related to the alveoli. Further, the arrow R1 schematically shows how CO2 is diffused and excreted in the alveoli. The vertical length of the alveolar model 700 represents the capacity of the FRC space, and the horizontal length of the alveolar model 700 represents the alveolar air concentration FACO2. At the end of inspiration (End Inspiration), the alveolar air concentration FACO2 is FAminCO2, so the total volume of CO2 gas in the FRC space is expressed as FRC × FAminCO2. At the end of exhalation (End Expiration), the alveolar air concentration FACO2 is FAmaxCO2, so the total volume of CO2 gas in the FRC space is expressed as FRC × FAmaxCO2. Between the end of inspiration and the end of exhalation (Mid Expiration), CO2 is diffused and excreted in the alveoli, and the total volume of CO2 gas in the FRC space is represented by FRC × FAmidCO2. FAmidCO2 is larger than FAminCO2 and smaller than FAmaxCO2. In this way, in the FRC space where the vertical length is constant, the horizontal length alveolar air concentration FACO2 changes between FAminCO2 and FAmaxCO2, and it is the one-time excretion of CO2 that promotes diffusion from the pulmonary capillary blood. The amount is VCO2.

FIG. 8 is a diagram showing a model of respiratory fluctuation of alveolar air CO2 partial pressure and diffusion flow rate / diffusion amount of CO2. In FIG. 8, the time-series waveform of the partial pressure PCO2 is shown on the upper side, and the CO2 diffusion flow rate V. The time-series waveform of CO2 is shown, in which "EXP." Represents the expiratory period and "INSP." Represents the inspiratory period.

In FIG. 8, the abbreviations and their explanations are as follows.
PvCO2: Mixed venous blood CO2 partial pressure PACO2: Alveolar air CO2 partial pressure PAmaxCO2: Maximum alveolar mood pressure PAminCO2: Minimum alveolar mood pressure PAmeanCO2: Average alveolar mood pressure = (PAmaxCO2 + PAminCO2) / 2
ΔPACO2: Alveolar mood pressure difference = PAmaxCO2-PAminCO2. ΔPACO2 / 2 is the alveolar air mean pressure difference V. CO2: CO2 diffusion flow rate = lung diffusion capacity DL × partial pressure difference ΔPACO2 (Fick's law. DL is a constant of alveolar membrane and gas characteristics)
V. CO2mean: Average CO2 diffusion flow rate = Lung diffusion capacity DL × Alveolar air average partial pressure difference ΔPACO2 / 2
VICO2: Inspiratory phase diffusion CO2 amount = V. CO2mean x intake time TI
VECO2: Expiratory phase diffusion CO2 amount = V. CO2mean x expiratory time TE
VCO2: CO2 excretion amount = VICO2 + VECO2 = V. CO2mean x one breath time T
As shown in the PCO2 graph of FIG. 8, the alveolar mood pressure PACO2, which reached an approximately equilibrium with the partial pressure of pulmonary capillary blood CO2 at the end of exhalation, reached the minimum at the end of inspiration due to the influx of new CO2-free inspires and was mixed. The difference in partial pressure from venous blood CO2 partial pressure PvCO2 is widened. As a result, CO2 diffuses from the blood to the alveoli and rises toward the end of exhalation toward the partial pressure of blood CO2 in the pulmonary capillaries. In this way, PACO2 respirably fluctuates between PAmaxCO2 and PAminCO2.

According to Fick's law, the diffusion flow rate of CO2 V. CO2 is proportional to the partial pressure difference (PvCO2-PACO2) between the mixed venous blood flowing into the pulmonary capillaries and the alveolar air. Since PACO2 fluctuates between PAmaxCO2 and PAminCO2 as described above, the partial pressure difference (see arrow R2) that actually drives the CO2 diffusion from the blood to the alveoli is (PvCO2-PAminCO2)-(PvCO2-PAmaxCO2). = PAmaxCO2-PAminCO2 = ΔPACO2. Thereby, the diffusion flow rate V. CO2 also fluctuates as shown in the graph, and this area (integral of flow rate) represents the amount of CO2 diffusion, and CO2 single excretion amount VCO2 = inspiratory phase diffusion amount VICO2 + expiratory phase diffusion amount VECO2. Further, since the average partial pressure difference driving the diffusion is (PAmaxCO2-PAminCO2) / 2 = ΔPACO2 / 2, the average diffusion flow rate V. Since CO2mean = DL × ΔPACO2 / 2, VICO2 + VECO2 = V. CO2men x TI + V. CO2mean × TE = V. CO2mean × T = DL × ΔPACO2 / 2 × T = VCO2. Although FRC = VCO2 / (FAmaxCO2-FAminCO2) as in the equation (2), FRC = VCO2 / ΔFACO2 = VCO2 / (ΔPACO2 / 713) = (DL × ΔPACO2 / 2 × T) from the above equation. / (ΔPACO2 / 713) = DL × T × 713/2, and it can be seen that FRC is proportional to the lung diffusion capacity DL and one breathing time T. In addition, "713" of the above formula is a value obtained from the above-mentioned conversion constant k = (760-47) as a saturated water vapor pressure of 47 mmHg when the body temperature is 37 ° C. and the atmospheric pressure is 760 mmHg.

Next, another example of the method of calculating the functional residual air amount FRC will be described.

FIG. 9 is an explanatory diagram of another example of the calculation method of the functional residual air amount FRC.

In FIG. 9, the left is an alveolar air model at the end of inspiration. At the end of inspiration, the tidal volume VTE is sent to the FRC space, which reduces the alveolar air CO2 concentration to the minimum concentration FAminCO2. Since CO2 does not exist in the dead space VD, the total amount of CO2 at this time is (FRC + VA) × FAminCO2, and the partial pressure difference between the partial pressure PcCO2 and FAminCO2 of the lung capillary blood in contact with the alveoli causes the blood to go to the alveoli. VCO2 diffuses rapidly.

In FIG. 9, the right is a model of alveolar air and exhalation at the end of exhalation after diffusion, and the total amount of CO2 at this time is (FRC + VA) × FAmaxCO2.

The equation of the above model is as follows.
(FRC + VA) x FAminCO2 + VCO2 = (FRC + VA) x FAmaxCO2
If you transform this,
(FRC + VA) × (FAmaxCO2-FAminCO2) = VCO2
Therefore, the functional residual air amount FRC is as follows.
FRC = VCO2 / (FAmaxCO2-FAminCO2) -VA
That is, the functional residual air volume FRC can also be derived as a value obtained by subtracting the alveolar ventilation volume VA from VCO2 / (FAmaxCO2-FAminCO2).

More specifically, the change in CO2 partial pressure of alveolar air, which is the driving force of diffusion, is produced by tidal volume VT (VTI, VTE). Since the dead space volume VD, which is a part of the tidal volume VT, is rebreathed, the gas exchange function for that amount is ineffective, and the rest is the effective alveolar ventilation volume VA (= VTE-VD). This VA is added to the functional residual air volume FRC to create the above-mentioned partial pressure change. Therefore, it is also possible to obtain the functional residual air volume FRC by correcting for the alveolar ventilation volume VA. The alveolar ventilation volume VA can be calculated by obtaining the point G in FIGS. 5 and 6 as described above.

From the viewpoint of obtaining the value of the functional residual air amount FRC as the volume, it is preferable that FRC = VCO2 / (FAmaxCO2-FAminCO2) -VA, but FRC = VCO2 / (FAmaxCO2-FAminCO2) also functions. There is no particular problem from the viewpoint of monitoring the target residual air volume FRC (evaluation of CO2 excretion function of the lungs).

By the way, conventionally, the main FRC measurement methods include a helium closed circuit method, a body prestimograph method, a nitrogen wash-out open circuit method, an open circuit method using sulfur hexafluoride gas SF6, and an estimation method by CT cross-sectional area image analysis. .. The helium closed circuit method is a method in which blood-insoluble gas He of a known concentration is breathed from a container of a known volume until the concentration in the container and the alveoli reach equilibrium, and the lung volume is estimated from the change in the concentration before and after. Is. In the body prestimograph method, a subject placed in a closed room with a known volume is made to breathe, and the pressure change in the closed room and the oral pressure change of the subject are equalized by Boyle's law (PV constant) to obtain lung volume. The method. Further, the nitrogen wash-out open circuit method is a method of breathing with pure oxygen to remove all nitrogen N2 in the lungs and estimating the residual air amount from the amount of the removed nitrogen. There is also an indirect method for estimating the change in nitrogen concentration from the oxygen and carbon dioxide concentrations. However, all of them are far from practical use at the bedside (surgical anesthesia, intensive care, ward).

In this respect, the FRC calculation method according to the present embodiment is an analysis method based on the volume capnogram analysis as described above. Therefore, bedside monitoring is possible with a compact, lightweight and simple device.

10A-10C are diagrams showing an example of FRC calculation during general anesthesia for pneumoperitoneum. In FIGS. 10A to 10C, time is taken on the horizontal axis, volume (left side) and pneumoperitoneum on / off (right side) are taken on the vertical axis, and the change mode 1002 of the functional residual air volume FRC and the pneumoperitoneum on The / off variation mode 1001 is shown.

During general anesthesia with pneumoperitoneum, the diaphragm presses on the thoracic cavity by applying abdominal pressure of 10 mmHg, so that the alveoli are less likely to swell and the functional residual air volume FRC tends to decrease. As shown in FIGS. 10A to 10C, changes in the functional residual air volume FRC due to on / off of the pneumoperitoneum are clearly captured. In particular, since atelectasis is likely to occur in a long-term pneumoperitoneum as shown in FIG. 10C, alveolar patency procedure (recruitment maneuver) is required on the way. According to the monitor system 200 according to the present embodiment, since the change in the functional residual air volume FRC can be clearly captured, it is possible to appropriately evaluate the decreasing tendency and the degree of decrease in the functional residual air volume FRC during general anesthesia of the abdomen. Can be expected.

Next, an operation example of the control device 3 will be described.

FIG. 11 is a flowchart showing an operation example for the FRC calculation process realized by the control device 3. The process shown in FIG. 11 may be executed at predetermined intervals after the initialization process.

In step S110, the control device 3 acquires data from the flow sensor 13 and the respiratory gas sensor 14.

In step S112, the control device 3 generates (draws) a volume capnogram on the XY coordinates with the concentration F as the X-axis and the ventilation volume V as the Y-axis based on the data obtained in step S110. The volume capnogram may be drawn in such a manner that it overwrites the volume capnogram associated with the previous breath.

In step S114, the control device 3 determines whether or not the exhaled-end CO2 concentration FETCO2 is obtained based on the volume capnogram drawn in step S112. If the determination result is "YES", the process proceeds to step S116, and in other cases, the processing of the current cycle ends.

In step S116, the control device 3 executes the FRC calculation process. An example of the FRC calculation process will be described later with reference to FIG.

In step S118, the control device 3 outputs the FRC calculated in step S116. The FRC output method may be as described above. The FRC may be output as a numerical value in a manner of being overwritten by the FRC related to the previous respiration, or may be output as a time-series waveform as shown in FIG. 10A or the like.

In step S120, the control device 3 records the FRC calculated in step S116. At this time, the control device 3 may record other parameters (CO2 single excretion amount VCO2, maximum alveolar air CO2 concentration FAmaxCO2, etc.) together with the FRC. Further, in this case, the control device 3 may record FRC data or the like in a file format.

FIG. 12 is a flowchart showing an example of the FRC calculation process (step S116 in FIG. 11).

In step S1160, the control device 3 calculates the tidal volume VTE based on the volume capnogram (volume capnogram related to the current respiration) drawn in step S112.

In step S1162, the control device 3 calculates the CO2 single excretion amount VCO2 based on the volume capnogram.

In step S1164, the control device 3 sets an inverse proportional curve (see FIG. 6) in which V = VCO2 / FCO2, a concentration F on the X axis, and a ventilation volume V based on the CO2 single excretion amount VCO2 calculated in step S1162. Generated on the XY coordinates with the Y axis. The XY coordinates that generate the inverse proportional curve may be the same as the XY coordinates on which the volume capnogram is drawn. Further, in the modified example, an inverse proportional curve (see FIG. 5) such that V = VCO2 / FCO2 + (VTI-VTE) may be generated.

In step S1166, the control device 3 calculates FAmaxCO2, which is the maximum alveolar air CO2 concentration, based on the volume capnogram drawn in step S112 and the inverse proportional curve obtained in step S1164. FAmaxCO2 is calculated as, for example, VCO2 / VA. The VA can be calculated by obtaining the point G (see FIG. 6).

In step S1168, the control device 3 identifies the point H with respect to the volume capnogram drawn in step S112. The point H is, as described above, the point where the rectangle inscribed in the volume capnogram is maximized.

In step S1170, the control device 3 calculates FAminCO2, which is the maximum alveolar air CO2 concentration, based on the point H obtained in step S1168. FAminCO2 is calculated as, for example, the X coordinate of the point H.

In step S1172, the control device 3 calculates the functional residual air amount FRC based on the VCO2 obtained in step S1162, the FAmaxCO2 obtained in step S1166, and the FAminCO2 obtained in step S1170. That is, the functional residual air amount FRC is calculated by FRC = VCO2 / (FAmaxCO2-FAminCO2). In another embodiment, the functional residual air amount FRC may be calculated by FRC = VCO2 / (FAmaxCO2-FAminCO2) -VA.

In this way, according to the processes shown in FIGS. 11 and 12, the functional residual air amount FRC is calculated in real time. This makes it possible to monitor the functional residual air volume FRC at the bedside, for example, during general anesthesia for pneumoperitoneum.

Although each embodiment has been described in detail above, the present invention is not limited to a specific embodiment, and various modifications and changes can be made within the scope of the claims. It is also possible to combine all or a plurality of the components of the above-described embodiment.

For example, in the above-described embodiment, the FRC is calculated using the concentration, but the FRC may be calculated using the partial pressure equivalently. This is because, as described above, the concentration and the partial pressure have a relationship of [partial pressure PCO2 = k × concentration FCO2] in the case of CO2 when the body temperature is 37 ° C. and the atmospheric pressure is 760 mmHg. Therefore, when the body temperature is 37 ° C. and the atmospheric pressure is 760 mmHg, the FRC may be calculated by FRC = k × VCO2 / (PAmaxCO2-PAminCO2) or FRC = k × VCO2 / (PAmaxCO2-PAminCO2) -VA. When the partial pressure is used, an inverse proportional curve including the relationship of V∝VCO2 / PCO2 may be used instead of the above-mentioned inverse proportional curve including the relationship of V = VCO2 / FCO2.

Further, in the above-described embodiment, the case where the above-mentioned monitor system 200 and the control method thereof are applied to the inhalation anesthesia system 100 having the circulation type breathing circuit 1 is exemplified, but the present invention is not limited thereto. For example, the monitor system 200 and its control method described above can be applied to an ICU, a ward, and a home-use respirator.

1 Circulation type breathing circuit 2 Gas supply device 3 Control device 11 Intake valve 12 Connector 13 Flow sensor 14 Breathing gas sensor 15 Exhalation valve 16 CO2 absorber canister 17 Ventilator 31 Storage device 32 Computing device 33 Input device 34 Display device 35 Interface (I / F)
36 Flow sensor circuit 37 Respiratory gas sensor drive circuit 100 Inhalation anesthesia system 200 Monitor system

Claims (10)

A flow sensor that continuously detects the flow of the patient's breathing gas, a breathing gas sensor that continuously detects the concentration of the component gas of the breathing gas, and a control device connected to the flow sensor and the breathing gas sensor. It is a control method of the equipped monitor system.
The control device relates to a single breath.
The concentration / partial pressure in two-dimensional coordinates is synchronized with V, which is the ventilation volume based on the measurement result of the flow sensor, and FCO2 or PCO2, which is the concentration or partial pressure of CO2 gas based on the measurement result of the breathing gas sensor. -Create a ventilation loop,
Obtained as VCO2, which is the amount of CO2 gas excreted, based on the area surrounded by the concentration / partial pressure-ventilation volume loop.
Using the VCO2, an inverse proportional curve including the relationship of V = VCO2 / FCO2 or V∝VCO2 / PCO2 is generated.
Based on the concentration / partial pressure-ventilation volume loop and the inverse proportional curve, the FRC, which is the functional residual air volume, is calculated.
A monitor system control method for outputting the calculated FRC. To calculate the FRC is to derive FAmaxCO2 or PAmaxCO2, which is the maximum alveolar air CO2 concentration or the maximum alveolar air CO2 partial pressure, and FAminCO2 or PAminCO2, which is the minimum alveolar air CO2 concentration or the minimum alveolar air CO2 partial pressure. The method for controlling a monitor system according to claim 1, which comprises. Claim 2 comprises calculating the FRC by dividing the VCO2 by the difference between the FAmaxCO2 and the FAminCO2, or the difference between the maximum alveolar CO2 partial pressure and the minimum alveolar CO2 partial pressure. The control method of the monitor system described. To calculate the FRC, divide the VCO2 by the difference between the FAmaxCO2 and the FAminCO2, or the difference between the maximum alveolar CO2 partial pressure and the minimum alveolar CO2 partial pressure, and by the alveolar ventilation volume. The control method of the monitoring system according to claim 2, which comprises subtracting a certain VA. Claiming that deriving the FAmaxCO2 or the PAmaxCO2 comprises obtaining the mixed breath concentration point of the CO2 gas and deriving the FAmaxCO2 or the PAmaxCO2 based on the inverse proportional curve and the mixed breath concentration point. The method for controlling a monitor system according to any one of 2 to 4. The control method for a monitor system according to claim 5, wherein the mixed exhaled breath concentration point is determined by a value obtained by dividing the VCO2 by the tidal volume VTE and the tidal volume VTE. Deriving the FAminCO2 or the PAminCO2 means deriving the concentration or the partial pressure of CO2 when the area of the rectangle inscribed in the concentration / partial pressure-ventilation loop is maximized as the FAminCO2 or the PAminCO2. The method for controlling a monitoring system according to any one of claims 2 to 6, which includes. The control method for a monitoring system according to any one of claims 1 to 7, wherein outputting the FRC includes displaying the FRC together with the concentration / partial pressure-ventilation volume loop on a display device. .. A flow sensor that continuously detects the flow of the patient's breathing gas, a breathing gas sensor that continuously detects the concentration of the component gas of the breathing gas, and a control device connected to the flow sensor and the breathing gas sensor. It is a equipped monitor system,
The control device relates to a single breath.
The concentration / partial pressure in two-dimensional coordinates is synchronized with V, which is the ventilation volume based on the measurement result of the flow sensor, and FCO2 or PCO2, which is the concentration or partial pressure of CO2 gas based on the measurement result of the breathing gas sensor. -Create a ventilation loop,
Obtained as VCO2, which is the amount of CO2 gas excreted, based on the area surrounded by the concentration / partial pressure-ventilation volume loop.
Using the VCO2, an inverse proportional curve including the relationship of V = VCO2 / FCO2 or V∝VCO2 / PCO2 is generated.
Based on the concentration / partial pressure-ventilation volume loop and the inverse proportional curve, the FRC, which is the functional residual air volume, is calculated.
A monitor system that outputs the calculated FRC. Measurement results related to one breath are obtained from a flow sensor that continuously detects the flow of the patient's breathing gas and a breathing gas sensor that continuously detects the concentration of the component gas of the breathing gas.
For the one breath, V, which is the ventilation volume based on the measurement result of the flow sensor, and FCO2 or PCO2, which is the concentration or partial pressure of CO2 gas based on the measurement result of the breathing gas sensor, are synchronized. Generate a concentration / partial pressure-ventilation loop on two-dimensional coordinates,
For the one breath, it is determined as VCO2, which is the excretion amount of the CO2 gas, based on the area surrounded by the concentration / partial pressure-ventilation volume loop.
For the single breath, the VCO2 is used to generate an inverse proportional curve containing the relationship V = VCO2 / FCO2 or V∝VCO2 / PCO2.
For the single breath, the FRC, which is the functional residual air volume, was calculated based on the concentration / partial pressure-ventilation volume loop and the inverse proportional curve.
The calculated FRC is output for each breath.
A program that causes a computer to perform processing.

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