JP2008000436A - Lung compliance estimation apparatus and estimation method and artificial respiratory apparatus provided with estimation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lung compliance estimation apparatus and estimation method capable of accurately obtaining the compliance of lungs. <P>SOLUTION: An airway flow rate QawO at the point T0 of time of starting support and airway resistance R estimated beforehand are multiplied and an intrapulmonary pressure PalvO (=R×Qaw0) at the point T0 of time of starting the support is computed. Also, the computed intrapulmonary pressure Palv0 at the point T0 of time of starting the support is subtracted from the airway pressure Paw2 at the point T2 of time of an occlusion end stage and a pressure deviation (Paw2-Palv0) is computed. On the basis of the pressure deviation (Paw2-Palv0), computation is carried out as the compliance of lungs of a patient. Immediately after the inspiration operation of the patient is started, a spontaneous breathing pressure Pmus indicating the breathing effort of the patient is extremely low. By using a detected result in such a state that the spontaneous breathing pressure Pmus is extremely low, the compliance of the lungs is accurately estimated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a compliance estimation apparatus for estimating compliance representing lung elasticity and a ventilator including the estimation apparatus.

  FIG. 9 is a graph showing simulation results for explaining a conventional lung compliance estimation method. As a conventional technique, there is a technique for estimating lung compliance C by using a ventilator and closing an exhalation valve and closing a breathing circuit at the end of inhalation of a patient when estimating a patient's lung compliance.

  The ventilator determines the time when the airway flow rate Qr of the support gas supplied to the patient's airway exceeds a predetermined inhalation trigger setting value as the inspiration trigger time T10, and starts the inspiration support operation from the inspiration trigger time T10. To do. Further, the ventilator determines a time point when the airway flow rate Qr of the support gas supplied to the patient's airway becomes less than a predetermined expiratory trigger setting value as an expiratory trigger time point T11, and an inspiratory support operation at the expiratory trigger time point T11. Exit.

In the prior art, when estimating the lung compliance, the airway pressure Paw10 at the inspiration trigger time T10 and the lung ventilation amount Vt10 are detected. Further, the inspiratory duct is closed from the expiration trigger time T11, and the airway pressure Paw12 and the lung ventilation amount Vt12 at the end of the occultation period T12 after about 300 msec from the expiration trigger time T11 are detected. The lung compliance C is estimated by the approximate expression shown in the following expression (a).
C = (Vt12−Vt10) / (Paw12−Paw10) (a)

  Here, C indicates lung compliance. Vt12 represents the lung ventilation at the end of the occultation period T12, and Vt10 represents the lung ventilation at the inspiration trigger time T10. Paw12 represents the airway pressure at the end of the occultation period T12, and Paw10 represents the airway pressure at the inspiration trigger time T10. In the formula (a), the spontaneous breathing pressure Pmus corresponding to the patient's inspiratory effort is not generated at the inspiration trigger time T10 and the occultation end time T12, and the airway pressure Paw and the intrapulmonary pressure Palv coincide with each other. If we assume that the equation holds.

  In the above-described prior art, the inspiration trigger time T10 may be delayed from the inspiration start time T0 when the patient starts the inhalation operation. In this case, the spontaneous breathing pressure Pmus is generated at the expiration trigger time T10, whereas the spontaneous breathing pressure Pmus is not generated at the occultation end point T12. Therefore, there is a problem that the lung compliance cannot be accurately estimated due to the influence of the spontaneous breathing pressure Pmus.

In the simulation result shown in FIG. 9, the lung compliance C obtained at the inspiration start time T0 when the spontaneous breathing pressure Pmus is not generated and the occultation end time T12 is (Vt12−Vt0) / (Palv12−Palv0) = ( 350−90) / (6.8−2.0) = 54.2 ml / (cmH ₂ O). On the other hand, according to the prior art, the lung compliance C obtained at the inspiration trigger time T10 and the occultation end time T12 is (Vt12−Vt10) / (Paw12−Paw10) = (350−80) / (6. 6-0) = 40.9 milliliters / (cmH ₂ O).

As described above, the estimated lung compliance C using the airway pressure Paw at the inspiration trigger time T10 and the occultation end time T12 is shifted from the actual lung compliance C due to the influence of the spontaneous breathing pressure Pmus. Will occur. In the simulation result of FIG. 9, the estimated compliance is about 13 ml / (cmH ₂ O) smaller than the actual compliance. In other words, the estimated compliance is 77% of the actual compliance, and the deviation from the actual compliance is large.

  Moreover, the state of the lung may be dynamic hyperinflation. The dynamic hyperinflation is a state in which the pressure in the lung is higher than the airway pressure at the inspiration start time T0, that is, the residual pressure exists in the lung. In this case, at the inhalation start time T0, the support gas flows through the airway in the direction of escape from the lungs. When the patient's respiration rate is high and the airway pressure R and compliance C are large, dynamic hyperinflation tends to occur.

  When the lung condition is dynamic hyperinflation, the pressure Palv in the lung may be higher than the airway pressure Paw at the time T0 when the patient starts the inhalation operation. In this case, the intrapulmonary pressure Palv10 tends to be larger than the airway pressure Paw10 at the expiration trigger time T10. Due to the fact that the intrapulmonary pressure Palv10 is greater than the airway pressure Paw10, there is a problem that the compliance cannot be estimated with high accuracy.

  FIG. 10 is a diagram showing a simulation result showing a change in the estimated compliance with respect to a change in the respiratory rate per minute of the patient. In FIG. 10, the vertical axis shows the estimated compliance, and the horizontal axis shows the number of breaths per minute on the horizontal axis. As shown in FIG. 10, as the patient's breathing rate per minute increases, the estimated compliance becomes smaller than the actual compliance. As described above, the conventional technique has a problem in that the lung compliance cannot be accurately estimated.

  Accordingly, an object of the present invention is to provide a lung compliance estimation apparatus and estimation method that can accurately determine lung compliance.

The present invention is a compliance estimation device for estimating the compliance of a patient's lungs using a ventilator for a patient performing a spontaneous breathing operation,
Support state detecting means for detecting a support start time T0 at which the ventilator starts an inhalation support operation simultaneously with the start of the patient's inhalation operation and a support end time T1 at which the ventilator ends the inhalation support operation;
From support end T0, until Okarujon period W _O the predetermined has elapsed, a closing means for closing the expiratory conduit for discharging the expiratory air discharged from a patient,
A flow rate detecting means for detecting an airway flow rate of the assisting gas flowing through the patient's airway;
Airway pressure detection means for detecting the airway pressure of the assisting gas flowing through the patient's airway;
Estimating means for estimating patient lung compliance,
The estimation means acquires the detection result from each detection means,
From the support start time T0 to the occultation end time T2 set at the end of the occultation period Wo, the volume of support gas (Vt2-Vt0) flowing into the patient's lung is calculated.
Multiplying the airway flow rate Qaw0 at the support start time T0 and the airway resistance R estimated in advance to calculate the intrapulmonary pressure Palv0 (= R · Qaw0) at the support start time T0,
By subtracting the calculated intrapulmonary pressure Palv0 at the support start time T0 from the airway pressure Paw2 at the end of the occultation period T2, a pressure deviation (Paw2-Palv0) is calculated,
The value ((Vt2-Vt0) / (Paw2-Palv0)) obtained by dividing the volume (Vt2-Vt0) of the assist gas flowing into the patient's lung by the pressure deviation (Paw2-Palv0) is the compliance of the patient's lungs. It is the compliance estimation apparatus characterized by calculating as follows.

  According to the present invention, immediately after the patient's inspiration is started, the spontaneous breathing pressure Pmus representing the patient's breathing effort is extremely small. As described above, by using the detection result in a state where the spontaneous breathing pressure Pmus is extremely small, the lung compliance can be accurately estimated. Further, based on the airway flow rate Qaw0 at the support start time T0, the pulmonary pressure Palv0 at the support start time T0 is obtained. As a result, as compared with the case where the airway pressure Paw0 at the support start time point T0 is used, the compliance of the lung can be obtained with high accuracy even when the residual pressure exists in the lung.

  Further, the present invention is characterized in that the airway resistance R used in the calculation process by the calculation means is an airway resistance R estimated in accordance with a patient's condition.

  According to the present invention, by using the airway resistance value R estimated according to the patient's condition, lung compliance according to the patient's condition can be estimated.

In the present invention, the airway resistance value R used in the calculation process by the calculation means is:
The airway resistance value R, which is fixed in advance, is used in the specified respiratory frequency period in which the patient's inspiratory operation frequency is equal to or less than a predetermined specified number of times since the start of inhalation support by the ventilator,
The airway resistance R estimated according to the patient's condition is used when the specified respiratory frequency period is exceeded after the start of inspiration support by the ventilator.

  According to the present invention, the fixed airway resistance is used in the specified respiratory rate period, and the estimated airway resistance R is not used for compliance estimation. Therefore, even when the estimated airway resistance R varies at the beginning of the support by the ventilator, it is possible to prevent the estimated airway resistance variation from affecting the estimated lung compliance.

Further, the present invention is a control device for controlling a gas supply servo mechanism of a ventilator for supplying a support gas containing oxygen to a patient's airway via an inspiratory line for a patient who performs a spontaneous breathing operation,
The control device controls the gas supply servomechanism based on the patient's lung compliance estimated by the compliance estimation device.

  According to the present invention, by controlling the gas supply servo mechanism using the lung compliance estimated by the lung compliance estimation apparatus described above, it is possible to suitably control the gas supply servo mechanism by improving the compliance estimation accuracy. It can be carried out.

Further, the present invention is a control device for controlling a gas supply servo mechanism for supplying a support gas containing oxygen to a patient's airway via an inspiratory line for a patient performing a spontaneous breathing operation,
Input means for inputting a compliance value of a patient's lung estimated by the compliance estimation device;
Storage means for storing a reference value of a patient's lung as a reference;
A selection means for selecting whether to use a patient lung compliance value estimated by the compliance estimation device or a patient lung compliance value stored by the storage means;
And a control means for controlling the gas supply servo mechanism based on a compliance value of a patient's lung selected by the selection means.

  According to the present invention, the selection means can select whether to use an estimated lung compliance value or a predetermined lung compliance value, thereby improving convenience.

Further, the present invention is a compliance estimation method for estimating the lung compliance of a patient using a ventilator for a patient performing a spontaneous breathing operation,
A support start time detection step of detecting a support time T0 at which the ventilator starts an inspiration support operation simultaneously with the patient's inhalation operation;
A flow rate detecting step of detecting the airway flow rate Qaw0 of the support gas flowing through the patient's airway at the start of support time T0 and starting the integration of the airway flow rate Qaw;
A support end time detection step of detecting a support end time T1 at which the respiratory muscles of the patient end the inspiration action;
From support end T1, until Okarujon period W _O the predetermined has elapsed, a closing step of closing the expiratory conduit,
Completion of the accumulation of the airway flow rate Qaw, and calculates the volume (Vt2-Vt0) of the support gas flowing into the patient's lung from the support start time T1 to the occultation end time T2 set at the end of the occultation period Wo. A volume calculation step to perform,
An airway pressure detecting step of detecting an airway pressure Paw2 at the end of the occultation period T2,
The calculated lung pressure Palv0 (= R · Qaw0) obtained by multiplying the airway flow rate Qaw0 at the support start time T0 and the predetermined airway resistance R is subtracted from the airway pressure Paw2 at the end of the occultation period T2 detected by the airway pressure detection step. Then, the pressure deviation (Paw2-Palv0) is obtained, and the value ((Vt2-Vt0) / (Paw2) obtained by dividing the volume (Vt2-Vt0) of the support gas calculated in the volume calculation step by the pressure deviation (Paw2-Palv0). An estimation step of calculating -Palv0)) as the patient's lung compliance;
An output step of outputting an estimation result.

  According to the present invention, the compliance of the lung can be accurately estimated by using the detection result in a state where the spontaneous breathing pressure Pmus is extremely small. Further, based on the airway flow rate Qaw0 at the support start time T0, the pulmonary pressure Palv0 at the support start time T0 is obtained. As a result, as compared with the case where the airway pressure Paw0 at the support start time point T0 is used, the compliance of the lung can be obtained with high accuracy even when the residual pressure exists in the lung.

Moreover, this invention is a program which makes a computer perform the said estimation method.
According to the present invention, a computer executes a program for executing the present invention. In this case, it is possible to increase the estimation accuracy for the lung compliance output by the computer.

The present invention is also a computer-readable storage medium that stores the program.
According to the present invention, the computer reads the program for executing the present invention stored in the storage medium and executes it. In this case, it is possible to increase the estimation accuracy for the lung compliance output by the computer.

  According to the first aspect of the present invention, lung compliance can be estimated with high accuracy. By accurately estimating the lung compliance, the patient's condition can be grasped with high accuracy, and a response corresponding to the lung compliance can be performed. For example, the patient's burden at the time of inhalation support can be reduced by performing the inhalation support of the patient based on the accurately estimated lung compliance.

  According to the second aspect of the present invention, the lung compliance is determined for each patient condition that changes every moment by determining the lung compliance using the airway resistance value R estimated according to the patient condition. be able to.

  According to the third aspect of the present invention, the airway resistance R used for obtaining the compliance is properly used in the specified respiratory frequency period and after the specified respiratory frequency period has elapsed. As a result, the estimated lung compliance prevents the influence of variations in estimated airway resistance at the beginning of the support, and suppresses the estimated variation in lung compliance.

  According to the present invention as set forth in claim 4, the ventilator is controlled based on the lung compliance estimated with high accuracy. Therefore, the control of the gas supply servo mechanism can be performed with high accuracy, and the burden on the patient with respect to the intake assist operation can be reduced.

  According to the fifth aspect of the present invention, the selection means selects whether to use an estimated lung compliance value or a predetermined lung compliance value according to the patient's condition. Can be improved.

  According to the sixth aspect of the present invention, lung compliance can be estimated with high accuracy. By accurately estimating the lung compliance, the patient's condition can be grasped with high accuracy, and a response corresponding to the lung compliance can be performed. For example, the patient's burden at the time of inhalation support can be reduced by performing the inhalation support of the patient based on the accurately estimated lung compliance.

  According to the seventh aspect of the present invention, it is possible to output accurate lung compliance by causing a computer to execute a program for realizing the above-described method.

  According to the eighth aspect of the present invention, it is possible to output the lung compliance with high accuracy by causing the computer to execute the program stored in the storage medium.

  FIG. 1 is a block diagram showing a ventilator 17 in which the compliance estimation apparatus according to the first embodiment of the present invention is incorporated. The ventilator 17 which is 1st Embodiment of this invention has an estimation function which estimates the compliance C of a patient's lung. In other words, the ventilator 17 also serves as a compliance estimation device.

  The ventilator 17 includes a ventilator main body 17 a and a control device main body 33. The ventilator main body 17 a includes a mounting member 24, a pump 22, a pump actuator 31, an exhalation valve 27, an inspiratory conduit 25, an expiratory conduit 26, and an expiratory valve actuator 32. In the present embodiment, the gas supply mechanism 20 that includes the pump 22 and the pump actuator 31 and can adjust the pressure of the discharged assist gas is configured.

  The attachment member 24 is attached to the patient to supply gas to the patient's airway, and an attachment hole communicating with the patient's airway is formed. The inspiratory duct 25 is a duct connecting the pump 22 and the mounting member 24, and guides the gas supplied from the pump 22 to the patient's airway. The exhalation duct 26 is a duct connecting the mounting member 24 and a discharge place outside the apparatus, and guides the gas flowing out from the patient's airway to the discharge place outside the apparatus. The pump 22 is driven by the pump actuator 31 to supply assist gas containing oxygen to the intake pipe 25. The exhalation valve 27 opens and closes the exhalation duct 32 when the valve body is displaced by the exhalation valve actuator 32.

  The ventilator 17 has an airway flow rate detection means 50 and an airway pressure detection means 60. The airway flow rate detection means 50 detects the flow rate of the support gas flowing through the inspiratory conduit 25 and the expiratory conduit 26. The airway pressure detection means 61 detects the pressure of the assist gas flowing through the inspiratory duct 25 and the expiratory duct 26, respectively.

  For example, a value (Qi−Qe) obtained by dividing the flow rate Qi of the support gas flowing toward the patient's lung through the inspiratory line 25 by the flow rate Qe of the support gas flowing toward the direction of exiting the exhalation line 26 from the patient's lung. Is referred to as airway flow rate Qaw. Further, during the patient's inspiration period, the pressure of the support gas in the exhalation duct 26 is the airway pressure Paw, and during the patient's exhalation period, the pressure of the support gas in the inhalation duct 26 is the airway pressure Paw. Each of the detection means 50 and 61 gives a signal indicating the detection result to the control device main body 33.

  The control device body 33 includes a computer. The control device main body 33 includes an interface 101, a calculation unit 102, a storage unit 103, and a storage unit 104. The interface 101 receives signals from the flow rate detection means 50 and the airway pressure detection means 61 and gives the signals to the calculation unit 102. The storage unit 104 stores a program to be executed by the control device main body 33, and the arithmetic unit 102 reads and executes the program stored in the storage unit 104, thereby performing an operation for controlling the ventilator main body 17a. Do. The control device main body 33 has a patient respiratory state monitoring function for detecting the respiratory state of the patient and an estimation function for estimating the airway resistance R and the compliance R of the patient.

  The ventilator 17 includes an input unit 39, an output unit 40, a pump servo amplifier 48, and an exhalation valve servo amplifier 47. The input means 39 is input with state values indicating the state of the patient, such as a patient's airway resistance R and elastance E, from a doctor or an administrator who manages the gas supply mechanism 20. The input means 39 receives a control parameter value for performing inspiration support, such as an amplification gain for assisting breathing. The input means 39 gives a signal indicating the input information to the control device body 33.

  The output means 40 is given a signal from the control device main body 33 and outputs the patient's condition, the inspiratory support condition, and the like. In the present embodiment, the output means 40 is realized by a display or the like. The output means 40 serves as an informing means for informing the spontaneous breathing pressure ^ Pmus estimated by the control device main body 33, the airway pressure, the lung compliance, and the like. Based on the display command signal received from the control device main body 33, the output means 40 displays a waveform indicating temporal changes such as the estimated spontaneous breathing pressure ^ Pmus on the display screen.

  The control device main body 33 calculates the support pressure of the support gas discharged from the pump and the open / closed state of the exhalation valve 27 based on the signals given from the detection means 50 and 61, and outputs the calculation result as a command signal. To do. The control device main body 33 gives a signal indicating the support pressure of the support gas discharged from the pump to the pump servo amplifier 48 as the first command signal. The pump servo amplifier 48 drives the pump actuator 31 according to the first command signal given from the control device main body 33 so that the pressure of the support gas discharged from the pump becomes the support pressure.

  The control device main body 33 gives a signal indicating the open / closed state of the exhalation valve 32 to the exhalation valve servo amplifier 32 as a second command signal. The exhalation-valve servo amplifier 32 drives the pump actuator 31 so that the pressure of the support gas discharged from the pump becomes the support pressure in accordance with the second command signal given from the control device main body 33. The servo amplifiers 47 and 48 may be included in the control device main body 33. Each servo amplifier 47, 48 is realized by an amplifier circuit.

When determining that the patient's breathing state is the inhalation state, the control device main body 33 provides the exhalation-valve servo amplifier 47 with a signal indicating a command to close the exhalation valve 27 and close the exhalation valve 26. Further, the support pressure is calculated as needed, and a signal indicating the calculated support pressure is given to the pump servo amplifier 48. As a result, a support gas having a predetermined support pressure can be supplied into the lungs via the intake duct 25 and the patient's airway. For example, on the basis of the airway flow rate Qaw detected by the flow rate detection means 50, the pressure of the support gas discharged from the pump is proportionally ventilated (
Control according to Proportional Assist Ventilation (abbreviation PAV method).

  When determining that the patient's breathing state is the exhalation state, the control device main body 33 provides the exhalation-valve servo amplifier 47 with a signal indicating a command for opening the exhalation valve 27 and opening the exhalation conduit 26. Further, the support pressure is calculated as needed, and a signal indicating the calculated support pressure is given to the pump servo amplifier 48. As a result, the pressure in the pipelines 25 and 26 is maintained at a predetermined value or more, for example, a positive end-expiratory pressure (abbreviated as PEEP pressure).

  The control device main body 33 has a function of detecting a respiratory state. Based on the detection results of the flow rate detection means 50 and the pressure detection means 61, the control device main body 33 determines the inspiration start time when the patient starts the inspiration operation and the end of inspiration when the patient finishes the inhalation operation, among the patient's respiration status The time can be determined. The control device main body 33 can determine the intake start time and the intake end time by using, for example, the technique disclosed in International Patent Application WO 2004/002561 A2.

  The control device main body 33 determines the time point when the differential value obtained by differentiating the time change of the airway flow rate Qaw is higher than a predetermined threshold value as the inhalation start time of the patient. Accordingly, even when the airway flow rate Qaw is less than or equal to zero, that is, when the airflow is flowing in the direction of being discharged from the lungs, the inhalation start time of the patient can be detected. Further, the control device main body 33 determines a time point at which the airway flow rate Qaw flowing in the direction toward the patient's lungs is less than a predetermined inhalation end threshold value as a patient inhalation end point. For example, 10% of the maximum airway flow rate is set as the inhalation end threshold value.

  The control device main body 33 according to the present embodiment determines the start of the patient's inhalation operation and starts the inspiration support operation at the same time. Further, the end of the inhalation support operation is determined at the same time as the end of the inhalation operation of the patient is determined. Therefore, the patient's inspiratory operation start time substantially coincides with the ventilator support operation start time T0. Further, the end point of the patient's inhalation operation almost coincides with the support operation start point T1 of the ventilator.

  FIG. 2 is a block diagram showing a configuration for realizing the lung compliance estimation function of the ventilator 17. The ventilator 17 is a compliance estimation device, which includes a support state detection unit 300, an occlusion unit 301, an airway resistance storage unit 302, an airway resistance estimation unit 303, a selection unit 304, a compliance estimation unit 305, and the flow rate. A detection means 50 and the pressure detection means 61 are included. The calculation unit 102 can realize the functions of the support state detection unit 300, the blocking unit 301, the airway resistance estimation unit 303, and the compliance estimation unit 305 described above by executing a program stored in the storage unit 103.

  The support state detection unit 300 determines the inhalation start time of the patient as the support start time T0 of the ventilator. The support state detection means 300 detects the end point of inhalation of the patient as the support end point T1 of the ventilator. The support state detection unit 300 gives a signal indicating the detected detection result to the compliance estimation unit 305 and the blocking unit 301.

  The blocking unit 301 is given a signal indicating the support end time T1 from the support state detection unit 300. When the closing unit 301 determines the support end time T1 in response to the signal from the support state detection unit 300, the closing unit 301 gives a command signal for closing the exhalation valve 27 to the exhalation valve servo amplifier 47. Further, when determining the support end time T1, the closing means 301 gives a command signal for stopping the pump drive to the pump servo amplifier 48. In this way, the closing means 301 stops the driving of the pump 22 and closes the exhalation duct 26. As time elapses from this state, an equilibrium state is reached where the pulmonary pressure Palv and the airway pressure Paw are balanced. For example, when about 250 to 300 msec has elapsed since the closing means 301 closed the expiration line 26, it can be approximated that the intrapulmonary pressure Palv and the airway pressure Paw are in an equilibrium state. The obstruction | occlusion means 301 will cancel | release obstruction | occlusion of the exhalation duct line 26, and will open the exhalation duct line 26, if the predetermined occultation period passes after obstructing the exhalation duct line 26. FIG.

  The airway resistance storage unit 302 stores the patient's airway resistance value input from the input unit 39 by a doctor or an administrator. The airway resistance estimation means 303 estimates the airway resistance R by executing a predetermined airway resistance estimation program. The selection unit 304 stores selection information indicating which of the airway resistance storage unit 302 and the airway resistance estimation unit 303 is used for estimating the compliance C. The compliance estimation unit 305 estimates patient compliance based on signals indicating detection results given from the flow rate detection unit 50, the pressure detection unit 61, and the respiratory state detection unit 300.

The compliance estimation means 305 estimates patient compliance according to the following arithmetic expression.
C = ((Vt2-Vt0) / (Paw2-R · Qaw0)) (1)

  Here, C indicates the patient's compliance that is estimated and calculated. (Vt2-Vt1) indicates the volume of the support gas that has flowed into the lungs of the patient from the support start time T1 to the end of the occultation time T2. The occultation end point T2 is a point set at the end of the occultation period Wo. For example, when the occultation period Wo is set to 260 msec, the occultation end point T2 is set to a point when 250 msec has elapsed from the support end point T1. Paw2 represents the airway pressure at the end of the occultation period T2. R is the airway resistance of the patient obtained in advance. This airway resistance is either the airway resistance stored in the airway resistance storage means 302 or the airway resistance estimated by the airway resistance estimation means 303. Qaw0 indicates the airway flow rate at the support start time T1.

  FIG. 3 is a graph showing simulation results for explaining the compliance estimation method of the present invention. FIG. 3 (1) shows the time change of the intrapulmonary pressure Palv shown by the simulation. FIG. 3 (2) shows the time change of the ventilation amount Vt of the support gas supplied into the lung. FIG. 3 (3) shows the time change of the airway pressure Paw. FIG. 3 (4) shows the time change of the airway flow rate Qaw. It is a flowchart which shows the compliance estimation procedure of the compliance estimation means 305.

  First, in step s0, patient inhalation support by the ventilator is started, and when a compliance estimation command is input from the input means, the process proceeds to step s1. In step s1, when the compliance estimation unit 305 determines the support start time T0 in response to the signal indicating the support start time T0 given from the support state detection unit 300, the process proceeds to step s2.

  In step s2, the compliance estimation unit 305 acquires the airway flow rate Qaw0 at the support start time T0 detected by the flow rate detection unit 50, starts integration of the airway flow rate Qaw, and proceeds to step s3. In step s3, if the occultation end time T2 is determined based on the signal indicating the support end time T1 given from the support state detection means 300, the process proceeds to step s4.

  In step s4, the compliance estimation unit 305 ends the integration of the airway flow rate Qaw acquired by the flow rate detection unit 50. This integrated value is the volume (Vt2-Vt0) of the support gas that has flowed into the patient's lungs from the support start time T1 to the occultation end time T2. The compliance estimating unit 305 obtains the airway pressure Paw2 by the pressure detecting unit 61. When the volume change of the assist gas in the lung and the airway pressure Paw2 are calculated in this way, the process proceeds to step s5.

  In step s5, the compliance estimation unit 305 calculates the compliance according to the above-described equation (1), and when the calculation is completed, the process proceeds to step s6. In step s6, the lung compliance calculated in step s5 is output as the calculation result, and the process returns to step s1. Thus, every time the patient starts the inhalation operation, steps s1 to s6 are repeated.

  When the compliance estimation unit 305 determines that a predetermined end condition is satisfied while performing the operations of steps s1 to s6, the compliance estimation unit 305 ends the compliance estimation operation. For example, when it is determined that a predetermined end condition is satisfied by giving an end command by the input means 39, the control operation is ended.

The simulation results shown in FIG. 3 use the same parameters as the simulation results shown in FIG. The lung compliance C estimated according to the present embodiment is (Vt12−Vt0) / (Paw2-R · Qaw0) = (350−90) / (6.6−0.02 · 90) = 54.1 ml. / (CmH ₂ O). The estimated compliance is almost the same, only about 0.1 ml / (cmH ₂ O) smaller than the actual compliance. In other words, the estimated compliance is 99% or more of the actual compliance, and the deviation from the actual compliance is very small. As described above, according to the present embodiment, it is possible to estimate the compliance with high accuracy.

  As described above, according to the present embodiment, immediately after the patient's inhalation operation is started, the spontaneous breathing pressure Pmus representing the patient's breathing effort is extremely small. Since the support start time T0 of the ventilator is almost the same as the inhalation start time of the patient, the spontaneous respiration pressure Pmus is extremely small at the support start time T0. As described above, the lung compliance can be accurately estimated by using the detection result at the time T0 when the spontaneous breathing pressure Pmus is extremely small.

  Further, the airway flow rate Qaw0 at the support start time T0 and the airway resistance R are multiplied to obtain the intrapulmonary pressure Palv0 at the support start time T0. As a result, compared with the case where the airway pressure Paw0 at the support start time point T0 is approximated as the intrapulmonary pressure Palv0, it is possible to cope with a state in which residual pressure exists in the lung, and the lung compliance can be obtained with high accuracy. . Therefore, as shown in FIG. 10, even when the patient's breathing frequency is increased, it is possible to suppress the estimated compliance from deviating from the actual compliance.

  In principle, the estimated compliance can be obtained for each inhalation operation of the patient. The compliance estimation means 305 can improve the reliability by setting the average value of the estimation results in a plurality of intake operations as the compliance estimation value. Further, the compliance estimation means 305 determines that the estimation result estimated by one intake operation is not normal as compared with the past estimation result (n times average, standard deviation) and a predetermined allowable normal range value. The estimation result may not be adopted as an estimation error. Further, if it is determined as a normal estimation result, it may be included in the estimation result for n times for calculating the moving average as the latest estimation result. In the present embodiment, 20 is used as the number of times n for obtaining the average value of the estimation results. Further, the occurrence of occultation for estimating the compliance C may not be performed every intake operation. For example, the estimation operation may be performed by generating an occultation for every Lth of the intake operation that is set at random in a predetermined intake operation interval using a random number. For example, the intake operation interval is set to an interval at which the intake operation is performed 7 to several tens of times as an example. As a result, the burden on the patient can be reduced compared to the case where occultation is generated for each inhalation operation.

  The compliance estimation means 305 obtains compliance using the airway resistance R estimated by the airway resistance estimation means 302, and uses the airway resistance value R estimated according to the patient's condition, thereby adjusting the patient's condition. The corresponding lung compliance can be estimated. Further, the compliance estimation means 305 uses the airway resistance R stored in the airway resistance storage means 301 so that the estimated lung compliance can be obtained when the airway resistance R estimated by the airway resistance estimation means 302 is unstable. It is possible to prevent the estimated variation in airway resistance from being affected.

  The selection means 304 stores selection information indicating which airway resistance of the airway resistance estimation means 302 and the airway resistance storage means 301 is used. The selection information is set by the input means 39 so that it can be changed by a doctor or the like. As a result, the administrator can select airway resistance for seeking compliance in accordance with the patient's condition and the like, and convenience can be improved. The airway resistance stored in the airway resistance storage unit 301 is a fixed value regardless of the patient's condition, and the magnitude may be input from the input unit 39.

  FIG. 5 is a flowchart showing a compliance estimation procedure of the compliance estimation unit 305 according to the second embodiment of the present invention. The second embodiment of the present invention has the same configuration as the ventilator of the first embodiment except that the estimation procedure of the compliance estimation means 305 is partially different. Therefore, the description of the same configuration is omitted.

  In the second embodiment, when the patient's inhalation support by the ventilator is started in step a0 and a compliance estimation command is input from the input means, the process proceeds to step a1. In step a1, it is determined whether a predetermined occultation condition is satisfied. For example, if it is determined that it is the Lth number of intake times selected at random within a predetermined number of intake time intervals, it is determined that the occultation condition is satisfied. If the occultation generation condition is satisfied, the process proceeds to step a2, and if not, step a1 is repeated. Steps a2 to a5 perform the same operations as steps s1 to s4 shown in FIG. 4, and proceed to step a6.

  In step a6, it is determined whether or not the number of inhalation movements of the patient is equal to or less than a predetermined number after the start of inspiration support by the ventilator. Alternatively, it is determined whether or not the number of effectively estimated airway resistances is equal to or less than a specified number. In the present embodiment, the specified number is set to 10. When the compliance estimating means 305 determines that the number of inhalation motions of the patient or the estimated number of airway resistances is equal to or less than the specified number, the compliance estimating unit 305 proceeds to step a7. In step a7, the compliance estimating unit 305 calculates the compliance using the fixed airway resistance R that is stored in the airway resistance storage unit 302 and is fixed in advance regardless of the patient's condition, in accordance with the above-described equation (1). When the calculation is completed, the process proceeds to step a8. In step a8, the calculated lung compliance is output as a calculation result, and the process returns to step a1.

  In step a6, when the compliance estimating means 305 determines that the number of inhalation motions of the patient or the estimated number of airway resistances exceeds the specified number, the process proceeds to step a9. In step a9, the compliance estimation unit 305 calculates the compliance using the estimated airway resistance R estimated by the airway resistance estimation unit 303 in accordance with the above-described equation (1). When the calculation is completed, the process proceeds to step a8. . In step a8, the calculated lung compliance is output as a calculation result, and the process returns to step a1.

  According to the present embodiment, a fixed airway resistance is used in the specified respiratory rate period, and the estimated airway resistance R is not used for compliance estimation. Therefore, even when the estimated airway resistance R varies at the beginning of the support by the ventilator, it is possible to prevent the estimated airway resistance variation from affecting the estimated lung compliance. Therefore, it is possible to suppress the estimated fluctuation in lung compliance.

  Further, when the specified respiratory frequency period is exceeded, the estimated airway resistance can be settled compared to the initial period. Thus, when the prescribed number of breaths is exceeded, the compliance can be calculated using the airway resistance R estimated according to the patient's condition, and the estimated accuracy of the estimated compliance can be improved.

  In addition, the estimated airway resistance can be further improved in reliability by using an average value of a plurality of estimation results as an estimated value of the airway resistance. If the estimation result estimated by one estimation operation is compared with the past estimation result (n times average, standard deviation) and a predetermined allowable normal range value, the estimation result is estimated. It may not be adopted as an error. Further, if it is determined as a normal estimation result, it may be included in the estimation result for n times for calculating the moving average as the latest estimation result. As a result, when the number of breaths exceeds the specified breath number period, the reliability of the estimated airway resistance can be increased.

  FIG. 6 is a graph showing the principle for estimating the airway resistance R. FIG. 6 (1) is a diagram showing the change over time of the airway pressure Paw. FIG. 6 (2) is a diagram showing the time change of the airway flow rate Qaw. The airway resistance estimating means 303 gives a discharge pressure command of the ventilator and intentionally applies a disturbance signal during the inhalation period of the patient. Then, the airway resistance R is detected based on at least one change data of the airway pressure, the airway flow rate, and the ventilation amount while the airway pressure is disturbed.

  For example, the airway resistance estimation means 303 minutely changes the pressure of the support gas supplied by the ventilator, and changes the pressure fluctuation value ΔPaw that is minutely changed and the flow fluctuation ΔQaw of the support gas caused by the pressure fluctuation. Obtained from the detection means 50 and 61. Next, the airway resistance R is estimated and calculated based on the acquired pressure fluctuation value ΔP and flow rate fluctuation ΔQaw. For example, ΔPaw / ΔQaw is obtained. Such an airway resistance estimation method can use an existing technique. For example, the airway resistance R may be estimated using the technique disclosed in JP-T-11-502755.

FIG. 7 is a graph showing the principle for _obtaining the support start time point T _onset . FIG. 7 (1) is a graph showing the time change of the airway flow rate Qaw, and FIG. 7 (2) is a graph showing the time change of the differential value Qaw dt obtained by differentiating the time change of the airway flow rate Qaw.

  When the patient starts the inhalation operation, the differential value Qaw dt, which is the time change of the flow rate of the support gas, increases beyond the predetermined inhalation start threshold value X1. This is a phenomenon that occurs both when the support gas is flowing in the direction toward the lungs and when the support gas is flowing in the direction of being discharged from the lungs.

In the present embodiment, the support state detection means 300 is based on the time change of the differential value Qaw dt of the flow rate Qaw of the support gas, and when the differential value Qaw dt of the flow rate Qaw of the support gas exceeds the intake start threshold value X1. Is detected as the support start time T. As a result, the support start time T _onset can be determined even when the support gas flows in the direction in which the support gas is discharged from the lungs at the support start time T _onset . Further, in addition to the airway flow rate Qaw, the support start time point T _onset may be obtained based on a differential value that is a temporal change amount of the spontaneous respiratory estimated value represented by (^ R · Qaw + ^ E · ∫Qaw). Further, the technique disclosed in the international patent application (WO 2004/002561 A2) may be used. Similarly, the time point when the change in the flow rate of the support gas or the differential value obtained by differentiating the estimated spontaneous breathing value falls below the predetermined intake end threshold value X2 can be detected as the support end time point T _offset . In addition, a mask 300 is set for the patient to exclude the change in the differential value of the airway flow rate Qaw caused by disturbance such as coughing and sneezing from the detection determination of the support start time point T _onset . This makes it possible to accurately determine the support start time T _onset .

  Further, in addition to the determination based on the airway flow rate, the support state detection unit 300 may be realized by using a detection unit that detects a change state that changes when the patient starts inspiration. For example, the patient's support start time may be obtained by causing a pressure sensor or a position sensor for detecting the movement of the diaphragm to enter the lung using a catheter and directly obtaining the pressure in the lung. As described above, the support state detection unit 300 may be realized using a detection unit capable of entering the lung.

FIG. 8 is a block diagram showing the entire system including the ventilator 17 and the patient 2. In the present embodiment, the ventilator performs the PAV method as an inspiration support method. Specifically, the ventilator determines the target pressure value Pin by the following equation (2).
Pin == A · ^ Pmus = A (^ R · Qaw + ^ E · ∫Qaw) (2)

  Here, Pin indicates the target pressure value of the support gas discharged from the gas supply mechanism toward the airway, and A indicates the amplification gain. ^ Pmus indicates the estimated spontaneous breathing pressure. ^ R indicates the estimated patient airway resistance, and ^ E indicates the estimated patient's lung elastance. Qaw indicates the airway flow rate. Further, ∫Qaw indicates the volume of the support gas supplied into the lung from the inspiration support start time T0. Lung elastance E is the reciprocal of compliance C. Compliance C and airway resistance R can be obtained with high accuracy by the above-described compliance estimation means 305. By appropriately setting the amplification gain A, inspiration can be achieved with spontaneous respiratory pressure Pmus, that is, a force proportional to the patient's respiratory effort. Support operation can be performed. In addition, the stability of the ventilator can be improved. The average value of the estimation results sequentially estimated by the compliance estimation unit 305 may be automatically substituted for the elastance of the above-described arithmetic expression.

  The ventilator may determine the target pressure Pin based on an arithmetic expression other than the expression (2). For example, the ventilator may have an observer as a control system configuration. In this case, the observer uses the respiratory organ model that models the system including the respiratory organ of the patient, and calculates the airway flow rate as the estimated flow rate {circumflex over (Q)} w when the target pressure Pin is given to the pump servo amplifier. The ventilator calculates the target pressure Pin based on the deviation ΔQaw between the estimated flow rate ^ Qaw estimated by the observer and the airway flow rate Qaw detected by the detection means. By using the lung compliance estimated by the compliance estimating means for the respiratory organ model set in the observer, the observer estimation accuracy can be improved and the control performance can be improved. This can improve the stability of the ventilator.

  As still another embodiment of the present invention, a ventilator that also serves as a compliance estimation apparatus includes compliance storage means and selection means. The compliance storage means stores a compliance value of the patient's lung. The selection means stores selection information for selecting which of the lung compliance values stored by the storage means is to be used. An administrator or the like can select selection information stored in the selection means. With this, in the inspiratory support operation in the ventilator, a doctor or the like can select whether to use compliance estimated according to the patient's condition or compliance that is fixed regardless of the patient's condition, Convenience can be improved. Further, as shown in FIG. 5, when the estimated compliance value is smaller than a predetermined threshold value, a fixed compliance value is used, and when the estimated value is larger than the threshold value, the estimated compliance value is used. You may set the program of a calculating part to.

  The embodiment of the present invention described above is merely an example of the present invention, and the configuration can be changed within the scope of the invention. For example, in the present embodiment, the ventilator also serves as the compliance estimation device, but the compliance estimation device may be formed separately from the ventilator. In the present embodiment, the ventilator performs the inspiration support according to the PAV method. However, the present invention is not limited to this, and the inhalation support may be performed according to another inspiration support method other than the PAV method. The present invention also relates to a compliance estimation device, and the structure of the ventilator is not particularly limited. Moreover, a well-known technique can be used suitably about the detection means disclosed in this Embodiment, and the detection means which detects a patient's inhalation start operation | movement, and the detection means which detects a patient's airway resistance. Further, the present invention is effective when the intrapulmonary pressure Palv0 becomes higher than the airway pressure Paw at the support start time T0, but can be applied to other cases.

  In addition to the compliance estimation apparatus and the estimation method, the present invention includes a program for causing a computer to execute the estimation method and a computer-readable storage medium that stores the program.

It is a block diagram which shows the ventilator 17 in which the compliance estimation apparatus which is 1st Embodiment of this invention is integrated. It is a block diagram which shows the structure which implement | achieves the compliance estimation function of the lung of the ventilator. It is a graph which shows the simulation result for demonstrating the compliance estimation method of this invention. It is a flowchart which shows the compliance estimation procedure of the compliance estimation means 305. It is a flowchart which shows the compliance estimation procedure of the compliance estimation means 305 which is 2nd Embodiment of this invention. It is a graph which shows the principle for estimating the airway resistance R. It is a graph which shows the principle for calculating _| requiring support start time _Tonset . 2 is a block diagram showing an entire system including a ventilator 17 and a patient 2. FIG. It is a graph which shows the simulation result for demonstrating the compliance estimation method of the lung of a prior art. It is a figure which shows the simulation result which shows the change of the estimated compliance with respect to the patient's respiration rate change per minute.

Explanation of symbols

17 ventilator 50 flow rate detection means 61 pressure detection means 300 support state detection means 301 obstruction means 302 airway resistance storage means 303 airway resistance estimation means 304 selection means 305 compliance estimation means

Claims (8)

A compliance estimation device that estimates a patient's lung compliance using a ventilator for a patient performing a spontaneous breathing operation,
Support state detecting means for detecting a support start time T0 at which the ventilator starts an inhalation support operation simultaneously with the start of the patient's inhalation operation and a support end time T1 at which the ventilator ends the inhalation support operation;
From support end T0, until Okarujon period W _O the predetermined has elapsed, a closing means for closing the expiratory conduit for discharging the expiratory air discharged from a patient,
A flow rate detecting means for detecting an airway flow rate of the assisting gas flowing through the patient's airway;
Airway pressure detection means for detecting the airway pressure of the assisting gas flowing through the patient's airway;
Estimating means for estimating patient lung compliance,
The estimation means acquires the detection result from each detection means,
From the support start time T0 to the occultation end time T2 set at the end of the occultation period Wo, the volume of support gas (Vt2-Vt0) flowing into the patient's lung is calculated.
Multiplying the airway flow rate Qaw0 at the support start time T0 and the airway resistance R estimated in advance to calculate the intrapulmonary pressure Palv0 (= R · Qaw0) at the support start time T0,
By subtracting the calculated intrapulmonary pressure Palv0 at the support start time T0 from the airway pressure Paw2 at the end of the occultation period T2, a pressure deviation (Paw2-Palv0) is calculated,
The value ((Vt2-Vt0) / (Paw2-Palv0)) obtained by dividing the volume (Vt2-Vt0) of the assist gas flowing into the patient's lung by the pressure deviation (Paw2-Palv0) is the compliance of the patient's lungs. A compliance estimation device that calculates as follows.   The compliance estimation apparatus according to claim 1, wherein the airway resistance R used in the calculation process by the calculation means is an airway resistance R estimated according to a patient's condition. The airway resistance value R used in the calculation process in the calculation means is:
The airway resistance value R, which is fixed in advance, is used in the specified respiratory frequency period in which the patient's inspiratory operation frequency is equal to or less than a predetermined specified number of times since the start of inhalation support by the ventilator,
The compliance estimation apparatus according to claim 1, wherein an airway resistance R estimated according to a patient's condition is used when the specified respiratory frequency period is exceeded after the start of inspiration support by a ventilator. A control device for controlling a gas supply servomechanism of a ventilator that supplies a support gas containing oxygen to a patient's airway via an inspiratory line for a patient performing a spontaneous breathing operation,
The control apparatus which controls a gas supply servo mechanism based on the patient's lung compliance estimated by the compliance estimation apparatus as described in any one of Claims 1-3. A control device for controlling a gas supply servo mechanism for supplying a support gas containing oxygen to a patient's airway via an inspiratory line for a patient performing a spontaneous breathing operation,
Input means for inputting a compliance value of a patient's lung estimated by the compliance estimation device according to any one of claims 1 to 3,
Storage means for storing a reference value of a patient's lung as a reference;
A selection means for selecting whether to use a patient lung compliance value estimated by the compliance estimation device or a patient lung compliance value stored by the storage means;
And a control means for controlling the gas supply servo mechanism based on a compliance value of the lungs of the patient selected by the selection means. A compliance estimation method for estimating compliance of a patient's lungs using a ventilator for a patient performing spontaneous breathing motion,
A support start time detection step of detecting a support time T0 at which the ventilator starts an inspiration support operation simultaneously with the patient's inhalation operation;
A flow rate detecting step of detecting the airway flow rate Qaw0 of the support gas flowing through the patient's airway at the start of support time T0 and starting the integration of the airway flow rate Qaw;
A support end time detection step of detecting a support end time T1 at which the respiratory muscles of the patient end the inspiration action;
From support end T1, until Okarujon period W _O the predetermined has elapsed, a closing step of closing the expiratory conduit,
Completion of the accumulation of the airway flow rate Qaw, and calculates the volume (Vt2-Vt0) of the support gas flowing into the patient's lung from the support start time T1 to the occultation end time T2 set at the end of the occultation period Wo. A volume calculation step to perform,
An airway pressure detecting step of detecting an airway pressure Paw2 at the end of the occultation period T2,
The calculated lung pressure Palv0 (= R · Qaw0) obtained by multiplying the airway flow rate Qaw0 at the support start time T0 and the predetermined airway resistance R is subtracted from the airway pressure Paw2 at the end of the occultation period T2 detected by the airway pressure detection step. Then, the pressure deviation (Paw2-Palv0) is obtained, and the value ((Vt2-Vt0) / (Paw2) obtained by dividing the volume (Vt2-Vt0) of the support gas calculated in the volume calculation step by the pressure deviation (Paw2-Palv0). An estimation step of calculating -Palv0)) as the patient's lung compliance;
A compliance estimation method comprising: an output step of outputting an estimation result.   A program for causing a computer to execute the estimation method according to claim 6.   A computer-readable storage medium storing the program according to claim 7.

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