JP2000175886A - Method and apparatus for processing ventilation data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain C(=1/E) and R even when a patient connected with a respirator performs spontaneous respiration. SOLUTION: Driving pressure of a respirator 1 is measured by means of a pressure sensor 4 at a plurality of points in time and respiration flow rate of a patient amd respiration vol. of the patient in a conduit 2a are measured based on output of a flow rate sensor 5. In this case, measured driving pressure, flow rate and vol. are substituted into a related equation of a linear function between E (a reciprocal of compliance) and R (a respiratory tract resistance) which is held when there exists no spontaneous respiration and has the driving pressure of the respirator 1, the flow rate in the conduit 2a and respiration vol. of the patient as constants to obtain the related equation at each point and points of intersection of a group of straight lines expressing these related equations in the E-R coordinate are obtd. and the point of intersection with the highest frequency is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an output of a pressure sensor for detecting a pressure in a breathing circuit near a mouth of a patient connected to a ventilator and an output of a flow sensor for detecting a respiratory flow rate of the patient. The present invention relates to a method and apparatus for processing ventilation data.

[0002]

2. Description of the Related Art From the viewpoint of ventilation dynamics, compliance C and respiratory resistance (airway resistance) R are mentioned as important parameters for managing the respiration of a patient under a respirator. When a breathing circuit is considered in terms of ventilation dynamics, an equivalent circuit is as shown in FIG. Where the loads are C and R,
The drive sources are the patient's respiratory muscle pressure (general term for respiratory muscle pressure by diaphragm, intercostal muscle, etc.) Pmus and the respirator's drive pressure (respirator pressure) Paw.

According to this configuration, it can be said that a necessary ventilation volume is secured while assisting the respiratory muscle pressure (spontaneous respiratory pressure) Pmus with the respirator pressure Paw according to the patient's C and R. . C and R often change toward weaning. Therefore, knowing the loads C and R whenever necessary is important from the viewpoint of respiratory management, particularly from the viewpoint of ventilation dynamics.

Several methods have been proposed for obtaining C and R, but none of them can measure the spontaneous respiratory pressure Pmus.
There was no spontaneous breathing, that is, it was determined with the condition of Pmus = 0.

Here, a conventional method of calculating C and R by the least square method will be described. First, in the equivalent circuit of FIG. 8, assuming that C and R are constant (no change) during one breathing period, the following equation is established.

ΔPawi0 = R × fi + E × Vi + Pmus (1) where, E = 1 / C fi; flow rate at time i; flow Vi at time i; patient respiratory volume at time i; Set the value to zero. ΔPawi0; equivalent ΔPaw at time i. ΔPaw = Paw-PEEP
(PEEP; positive end-expiratory pres
sure) Pmusi; Pmus at time i

Let ΔPaw at the time i measured be ΔPawi, calculate the square of the difference from ΔPawi0 in equation (1), and calculate
Let S be the sum of the breathing periods. Where there is no spontaneous breathing,
That is, if Pmusi = 0, then S = Σ (ΔPawi- ΔPawi0) ² = Σ (ΔPawi- R × fi- E × Vi) ² ... (2) (2) Since E or R is convex downward, The condition for minimizing S is ∂S / ∂R = 0 and ∂S / ∂E = 0… (3) Equation (3) is a simultaneous equation where E and R are unknowns.
, R. However, when there is spontaneous breathing, the respiratory muscle pressure Pmus is generated, and Pmus cannot be measured, so that E and R cannot be measured accurately.

[0008]

Conventionally, Pm
Since E (= 1 / C) and R were obtained assuming us = 0, these values could not be obtained accurately when there was spontaneous breathing.

An object of the present invention is to accurately obtain E (= 1 / C) and R even when spontaneous breathing is present.

[0010]

The principle of the present invention will be described. In equation (1), Pmusi = 0, ΔPawi0 = ΔPawi, and rearranging E and R, E = − (fi / vi) × R + ΔPawi / Vi (4) Equation (4) shows that at time i, E and R A linear function of R, with the E axis and
Expressed in rectangular coordinates on the R axis.

If there is no spontaneous breathing during one breathing period, the entire straight line is drawn as shown in FIG. The P point is
The points that do not change during one breathing period, that is, E and R to be obtained are shown. Since E and R are constant and there is no spontaneous breathing
This is because equation (4) holds.

On the other hand, the straight line at the time when there is spontaneous breathing is (4)
The formula does not hold and does not pass through point P. Also, Pmus always fluctuates and does not pass through fixed points.

However, during one breathing period, there is a time when there is no spontaneous breathing, so that a certain point is passed at that time, and even if there is some spontaneous breathing, there is a certain fixed concentration point. become. FIG. 3 shows the concentration point Q in such a case. The present invention has been made based on the above principle.

According to a first aspect of the present invention, an output of a pressure sensor for detecting a pressure in a respiratory circuit near a mouth of a patient connected to a ventilator and an output of a flow sensor for detecting a respiratory flow rate of the patient are provided. A method of processing ventilation data,
At a plurality of points in time, the driving pressure of the ventilator is measured by the pressure sensor, the respiratory flow rate and the patient's respiratory volume of the patient are measured based on the output of the flow sensor, and this is established when there is no spontaneous breathing. The driving pressure, flow rate and volume measured by the relational expression of the linear function of E (reciprocal of compliance) and R (airway resistance), where the driving pressure of the ventilator, the respiratory flow of the patient, and the patient's respiratory volume are constants. Is substituted to find the relational expressions at each time point, find the intersection of the straight line group showing these relational expressions in the ER coordinates, and find the intersection with the highest frequency.

According to a second aspect of the present invention, an output of a pressure sensor for detecting a pressure in a respiratory circuit near a mouth of a patient connected to a ventilator and an output of a flow sensor for detecting a respiratory flow rate of the patient are provided. A ventilation data processing device for processing,
At a plurality of points in time, the pressure sensor measures the driving pressure of the ventilator, and based on the output of the flow sensor, measuring means for measuring the patient's respiratory flow rate and patient respiratory volume, and if there is no spontaneous breathing It is determined by the measuring means to a relational expression of a linear function of E (reciprocal of compliance) and R (airway resistance), where the driving pressure of the ventilator, the respiratory flow of the patient, and the patient's respiratory volume are constants. Relational expression creating means for obtaining the relational expression at each time point by substituting the obtained driving pressure, flow rate and volume, intersection detecting means for obtaining an intersection of a group of straight lines indicating these relational expressions in the ER coordinates, and intersection detecting means And a highest frequency intersection detecting means for obtaining an intersection having the highest frequency among the obtained intersections.

[0016]

FIG. 4 is a diagram showing the overall configuration of a measurement system using the ventilation data processing device of the present invention. As shown in this figure, the patient's airway is connected to one end of a conduit 2a. The other end of the conduit 2 a is connected to a first port of the Y adapter 3. The second and third ports of the Y adapter 3 are connected to the inspiratory side and the expiratory side of the ventilator 1 via conduits 2b and 2c, respectively. The conduit 2a near the mouth of the patient is provided with a pressure sensor 4 for detecting the pressure in the conduit 2a, that is, the ventilator pressure Paw, and a flow sensor 5 for detecting the flow rate of the patient's expiration and inspiration. In practice, a differential pressure generating mechanism is provided in the conduit 2a, and the differential pressure is guided by two tubes to a pressure sensor installed at a location away from the mouth of the patient, thereby measuring the flow rate and pressure. However, here, both sensors are conceptually present at the mouth of the patient including such a sensor.

The outputs of the pressure sensor 4 and the flow sensor 5 are
The ventilation data processing device 6 adapted to reach the ventilation data processing device 6 is configured by a computer system as shown in FIG. That is, the ventilation data processing device 6
A CPU (Central Processing Unit) 7 for performing arithmetic control, a memory 8 for storing a processing program and necessary data or for temporarily storing data in the course of processing, a display means 9 for displaying data, The data to be displayed on the means 9 is C
The system includes an image processing unit 15 created under the control of the PU 8, input means 10 including a keyboard and the like, an input interface 11 for taking in external data into the system, and a system bus 12. Further, the A / D converters 13, 1
4, which perform A / D conversion of the output of the pressure sensor 4 and the output of the flow sensor 5 through the input interface 11.

Next, the operation of the measuring system thus configured will be described. FIG. 5 is a flowchart of a process performed by the ventilation data processing device 6. Description will be made with reference to this figure.

When the operation of the ventilation data processing device 6 is started, acquisition of Paw data and flow data is started from the outputs of the pressure sensor 4 and the flow sensor 5, and one breath is recognized (step 101). Here, the intake start point is recognized from the Flow waveform data and stored, and the time immediately before the current intake start point from the previous intake start point stored at the time when the next intake start point is recognized ( Until the end point of expiration) is recognized as one breath.

Next, it is determined whether the difference between the inspiratory volume and the expiratory volume in one recognized breath is equal to or less than a predetermined value a% (for example, 20%) (step 102). This is to eliminate unstable respiratory data. If the determination is no in this step, the process returns to step 101.

If the determination is yes in step 102, the process proceeds to step 103, where the volume waveform data is calculated. This calculation is performed by integrating Flow waveform data. At this time, the volume at the start of intake is set to zero. Here, Flow data, Paw data and Volume data of one breath are stored in the memory 8 and their waveforms are displayed on the display screen of the display means 9. An example is shown in FIG.

Next, PEEP is measured (step 10).
4). Ideally, it is the value of Paw at the end-tidal point. Actually, the end expiration point Paw falls sharply below the PEEP level due to the patient's expiratory effort (the ventilator detects this slight decrease and starts insufflation). For this reason, the flat part of Paw near the end of expiration is detected and this is defined as PEEP.

Next, a calculation range is determined (step 10).
5). The volume is very small near the start point of inspiration and near the end of expiration, and when this area is used as data, the calculation error becomes large (Vi is used in equation (5) in the next step).
Is the denominator), so it is excluded from the calculation range. Specifically, the amount of intake air is determined first, and during the intake period,
Volume gradually decreases during the expiration period while Volume is b% or more of inspiratory volume (for example, 20%), but c% of inspiratory volume
(For example, 20%) or more is set as the calculation range.

Next, for each data measurement time ti within the calculation range,
A relational expression between E and R is obtained (step 106). This relational expression is as follows. E = − (Fi / Vi) × R + ΔPawi / Vi… (5) where, E; elastance seen from the patient's mouth. Reciprocal of compliance. cmH2O / L. R; airway resistance as seen from the patient's mouth. cmH2O / L / s. Fi; Flow at time ti. L / s. Pawi; Paw at time ti. cmH2O. Vi; Volume at time ti. The start time of intake is set to zero. L. ΔPawi; pressure obtained by subtracting PEEP from Pawi at time ti. cmH2O
.

When this relational expression is represented on the orthogonal coordinates of the E-axis and the R-axis, it is a single straight line at one point in time, and it is a group of straight lines when represented for all times ti within the calculation range. Here, these relational expressions are stored in the memory 8 and displayed on the display screen of the display means 9. FIG. 7 shows an example of the display.

Next, the intersection of two straight lines in the straight line group is obtained by combining all the straight lines (step 107). However, combinations of straight line groups whose slopes near the end of the expiration period and the inspiration period are close to zero are excluded (intersection points are not determined).

The reason for excluding the expiration period is as follows. During the expiration period, the respiratory muscles are usually relaxed, in which case
Flow has a waveform according to the time constant of the CR of the patient. For this reason, on the ER plane, the line becomes exactly the same at any time,
This is because the calculation becomes impossible or the error increases. Also, the reason why the combination of straight lines near the end of the inspiration period is close to zero is excluded because the intersection points vary.

Specifically, the absolute value of the slope is d (sec- ¹ )
(Eg, 0.20) Calculate for combinations of straight lines greater than

Next, the intersection of the maximum frequency is obtained (step 108). That is, a frequency distribution is obtained for each of the obtained intersections E and R, and the E and R values having the highest frequency are obtained. However, the frequency distribution needs to be sharp to some extent. As a criterion for judging whether or not it is sharp, for example, if the variance with respect to the average value is c% or less (eg, 50%), it is regarded as sharp. These frequency distributions and the most frequent E
, R values are stored in the memory 8 and displayed on the display screen of the display means 9 (the frequency distribution is superimposed on a group of straight lines as shown in FIG. 7).

According to this embodiment, accurate data can be obtained because the respiratory data at the time of instability and the data near the inspiration start point and the end of expiration in one breath are excluded.

[0031]

According to the present invention, C (= 1 / E) and R can be accurately obtained even when a patient connected to a ventilator is breathing spontaneously.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a device of the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a diagram illustrating the principle of the present invention.

FIG. 4 is an overall view of a measurement system in which the device shown in FIG. 1 is used.

FIG. 5 is a flowchart for explaining the operation of the device shown in FIG. 1;

FIG. 6 is a view showing an example of data displayed on a display screen of a display means.

FIG. 7 is a view showing an example of data displayed on a display screen of a display means.

FIG. 8 is a diagram showing an equivalent circuit of a respiratory circuit based on ventilation dynamics.

[Explanation of symbols]

 Reference Signs List 4 pressure sensor 5 flow sensor 6 ventilation data processing device 7 CPU 8 memory 9 display means

Claims (2)

[Claims] 1. A ventilation data processing method for processing an output of a pressure sensor for detecting a pressure in a breathing circuit near a mouth of a patient connected to a ventilator and an output of a flow sensor for detecting a respiratory flow rate of the patient. At a plurality of times, the driving pressure of the ventilator is measured by the pressure sensor, and the respiratory flow rate and the patient's breathing volume of the patient are measured based on the output of the flow rate sensor, and there is no spontaneous breathing. Is established when the driving pressure of the ventilator, the patient's respiratory flow, and the patient's respiratory volume are constants.
Substituting the measured drive pressure, flow rate and volume into the relational expression of the linear function of (reciprocal of compliance) and R (airway resistance), obtains the relational expression at each time point, and calculates these relational expressions in the E-R coordinates. A method of processing ventilation data, wherein an intersection of the indicated straight line groups is obtained, and an intersection having the highest frequency is obtained. 2. A ventilation data processing device for processing an output of a pressure sensor for detecting a pressure in a breathing circuit near a mouth of a patient connected to a ventilator and an output of a flow sensor for detecting a respiratory flow rate of the patient. At a plurality of points in time, the pressure sensor measures the driving pressure of the ventilator, and the measuring means for measuring the patient's respiratory flow rate and the patient's respiratory volume based on the output of the flow rate sensor; It is established when there is no, and the driving pressure of the ventilator, the respiratory flow rate of the patient, the patient's respiratory volume as constants E
A relational expression creating means for substituting the driving pressure, flow rate and volume measured by the measuring means into a relational expression of a linear function of (reciprocal of compliance) and R (airway resistance) to obtain a relational expression at each time; -An intersection detecting means for obtaining an intersection of a group of straight lines indicating these relational expressions on the R coordinate; and a highest frequency intersection detecting means for obtaining an intersection having the highest frequency among the intersections obtained by the intersection detecting means. Characteristic ventilation data processing device.