JPH0819613A - Positive airway pressure breathing aid - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an improved respiratory-synchronized positive airway pressure type respiratory assist device that predicts the patient's willingness to breathe spontaneously and reduces errors in supply pressure due to control delay. A gas flow generating means for generating a gas flow, a conduit means for guiding the gas flow to an airway, a pressure control means for supplying the gas flow to the conduit means and supplying the airway with a variable pressure, and a gas flow for supplying the airway. Supply pressure target value generating means for generating the pressure target value of the, the flow rate detecting means for detecting the gas flow rate in the conduit, the pressure detecting means for detecting the gas pressure in the conduit, the detected flow rate value, the patient based on the pressure value Of the breathing motivation and calculating a predicted value of the breathing motivation, and an operation amount of the pressure control means such that the pressure supplied to the airway is asymptotic to the supply pressure target value. A positive airway pressure type artificial respiration device, comprising: a second calculation means for calculating the value from the respiratory motivation predicted value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a breathing-synchronized positive airway pressure type respiratory assist device for supplying a pressure gas such as air or high concentration oxygen gas to an output airway.

[0002]

2. Description of the Related Art A breathing assistance device applied to a patient capable of spontaneous breathing is required to have a sufficient ventilation capacity and not give discomfort or damage to the patient. From this viewpoint, it is desirable to perform respiratory assistance in synchronization with the patient's spontaneous breathing. As the auxiliary pattern in the inspiratory phase, in contrast to the conventional positive biphasic positive pressure (for example, JP-A-3-222963), the proportional assist type artificial respiration method (Japanese Patent Application No. 3-297733), etc., causes discomfort and damage to the patient. It is proposed from the viewpoint of reduction.

Thus, there is a need for a technique for finely changing the pressure or flow rate of the gas flow supplied to the patient during the inspiration period of the patient. As a method for realizing these, a method using negative feedback control (for example, Japanese Patent Laid-Open No. 4-2
63867) has been proposed.

[0004]

However, the conventional method has the following problems. That is, generally, the ventilator provided with the gas flow generation means, the conduit means, the pressure control means, etc. is a delay system from the viewpoint of pressure control. When using the proportional assist type artificial respiration method, it is desirable to change the supply pressure at intervals of about 100 msec or less from the viewpoint of reducing the dyspnea of the patient, but such fast control is performed by normal negative feedback control. The method is difficult to implement.

Therefore, control by an open loop can be considered. That is, a method is conceivable in which the relationship between the pressure to be applied and the pressure control means is quantitatively grasped according to the breathing state of the patient, and fast control is realized. For example, consider the case where it is desired to supply the pressure P after Tmsec. If the operation amount of the pressure control means is determined based on the current patient breathing state, the breathing state changes as the patient breathes during this period.
As a result, the operation amount of the pressure control means becomes excessive or insufficient. Therefore, the pressure supplied after Tmsec is P + ΔP including an error.

From the patient's point of view, the patient will feel uncomfortable and will be injured, for example, if he / she wants to inhale more and the supply amount is smaller, or if he / she does not want to inhale so much and the supply amount is too large. . The present invention solves the above problems, and in a breathing assistance device applied to a patient capable of spontaneous breathing, performs pressure assistance with an extremely small error in supply pressure due to control delay by predicting a patient's willingness to breathe. The object of the present invention is to provide a breathing assistance device that can reduce discomfort and damage to the patient and can provide a high therapeutic effect.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a positive airway pressure type artificial respirator, wherein gas flow generating means for generating a gas flow for breathing, conduit means for guiding the gas flow to the airway, and gas flow conduit are provided. Means for supplying a variable pressure to the airway, supply pressure target value generating means for generating a pressure target value of the gas flow supplied to the airway, and flow rate detection for continuously detecting the gas flow rate in the conduit. Means, a pressure detecting means for continuously detecting the gas pressure in the conduit, and the patient's willingness to breathe, that is, the willingness to inhale and / or exhale from the detected flow rate value and pressure value to calculate a predictive value of the willingness to breathe. And a second calculating means for calculating the operation amount of the pressure control means such that the pressure supplied to the airway asymptotically approaches the supply pressure target value from the supply pressure target value and the breathing willingness prediction value. And a calculation means, It is characterized by a door.

The flow rate and pressure of the gas flow supplied to the patient are detected by the flow rate detecting means and the pressure detecting means, respectively. The manner of their detection includes, for example, continuous, ie uninterrupted, but may be a sequence of data discretely measured with a sufficient number of samples during one breathing cycle of the patient.

The first calculation means predicts the patient's willingness to breathe from the detected flow rate value and pressure value, and calculates the predicted value of the willingness to breathe. For example, a value obtained by dividing the square root of the pressure value at a certain time by the flow rate value can be defined as the breathing willing value at that time. In this case, it is considered that the larger the value, the greater the patient's willingness to exhale, and the smaller the value, the greater the patient's willingness to inhale.

Breathing motivation values, or pressure and flow rate values,
It is possible to predict the breathing willingness value at a certain time in the future from the past change transition of. In the simplest case, the predicted value can be defined as an extrapolated value of a straight line obtained by linearly approximating the past change transition. Naturally, it is more desirable to define the predicted value as an extrapolated value of the curve obtained as a result of nonlinear approximation using a higher-order function.

The first calculation means can be easily realized by, for example, an electronic circuit (whether analog or digital).
Further, the measured flow rate value and the pressure value are input to a computer having at least a CPU and a memory via, for example, an A / D converter, and a predicted value is calculated and data is stored, which can be realized by software.

The second calculation means calculates an operation amount of the pressure control means such that the pressure supplied to the airway approaches the supply pressure target value from the supply pressure target value and the breathing willingness prediction value. This can be realized as follows, for example. The quantitative relationship between the supply pressure and the operation amount of the pressure control means is measured in advance using the breathing willingness value as a parameter. The result is stored as a data group of an appropriate form. Thereby, the operation amount of the pressure control means can be calculated from the supply pressure target value and the breathing willingness prediction value.

[0013]

When the pressure P is supplied after Tmsec, the respiratory state of the patient after Tmsec is predicted by using the first calculation means.
Based on the predicted value of the breathing willingness value, the operation amount of the pressure control means for applying the pressure P is calculated using the second calculation means. As a result, it is possible to reduce the excess or deficiency of the operation amount of the pressure control means and to significantly reduce the error in the pressure supplied after Tmsec.

[0014]

EXAMPLES The apparatus of the present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited thereto. FIG. 1 is a configuration diagram of a respiratory assistance device according to an embodiment of the present invention. FIG. 2 shows the relationship between the operation amount and the supply pressure value of the respiratory assistance device according to the embodiment of the present invention.

In the figure, reference numeral 1 is a gas flow generating unit having a variable rotation speed fan, and the rotation speed is adjusted to a desired fan output pressure within a range of several thousand to ten thousand rpm. 2 is a ventilator tube with an inner diameter of about 20 mm which is a conduit means, 3 is a supply pressure target value generation unit that outputs a supply pressure target value that is configured by an electronic circuit as a voltage signal, and 4 receives a manipulated variable as a voltage signal A pressure control unit composed of a stepping motor for controlling the supply pressure and a butterfly valve, 5 is a hot-wire flow meter which is a flow rate detecting means for continuously detecting the gas flow rate in the conduit,
6 is a semiconductor pressure sensor which is a pressure detecting means for continuously detecting the gas pressure in the conduit, 7 is a computer equipped with an A / D converter, a CPU and a memory, and outputs a predicted value of the breathing will as a voltage signal. Breathing motivation prediction value calculation unit, 8
Stores the data group of the result of measurement of the relationship between the supply pressure and the opening of the butterfly valve using the breathing will value as a parameter, calculates the butterfly valve opening from the target supply pressure value and the expected breathing will, and outputs it as a voltage signal. Operation amount calculation unit,
It consists of and.

The gas flow generated by the gas flow generation unit 1 is supplied to the patient by the conduit means 2 via the hot wire flow meter 5 and the semiconductor pressure sensor 6. Flow rate Q of the gas flow
The pressure P and the pressure P are measured by the hot-wire flow meter 5 and the semiconductor pressure sensor 6, respectively. The respiratory motivation predicted value calculation unit 7 is A
Respiration obtained by converting the measured pressure value signal C and the measured flow rate value signal B into a discrete data string at time intervals Ts (for example, 5 msec) via the / D converter, and gradually dividing the square root of the pressure value by the flow rate value. The motivation value is stored as a discrete data string, a straight line obtained by linearly approximating the changes in the past breathing motivation value including the current value is obtained, and as an extrapolated value, the specified time: D seconds
The predicted value signal E of the breathing motivation after (for example, 100 msec) is output.

The supply pressure target value generation unit 3 outputs a supply target pressure value signal A. The target pressure value Pt is, for example, K1, K
2, given by the following formula with C as a constant. Pt = K1∫Q ・ dt + K2 ・ Q (when patient is inspiring) Pt = C (when patient is exhaling)

The operation amount calculation unit 8 calculates the operation amount for making the supplied pressure value asymptotically closer to the target value by using the relationship between the operation amount which is the opening of the butterfly valve and the supply pressure value shown in FIG. To do. That is, the manipulated variable calculation unit 8 calculates the respiratory motivation predicted value signal E (see FIG. 2) and the supply target pressure value signal.
Upon receipt of A, the operation amount signal F, which is the opening of the butterfly valve, is output by referring to the memory contents in the table using those signal values as indexes. Specifically, the operation amount is determined as follows. In FIG. 2, it is now assumed that P = P1 at the opening θ1 of the butterfly valve (it is known that the current willingness to breathe is E1). Consider the case where P = P2 is desired after 100 msec. 100m
If the predicted value of the patient's willingness to breathe after sec is E2, it can be seen that θ = θ2 is required to set P = P2 at the value of the willingness to breathe E2.

The operation amount signal F is input to the stepping motor 4b and the controller, and the operation of rotating the stepping motor to reach the specified valve opening is performed to change the rotational position of the butterfly valve 4a, thereby changing the pressure control unit.
4 controls the supply pressure to the patient.

[0020]

As described in detail above, the present invention reduces the discomfort and damage of the patient by predicting the patient's willingness to breathe and performing pressure assistance with an extremely small error in the supply pressure due to the control delay. As a result, an artificial respiration device with high therapeutic effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic illustration of an embodiment of a respiratory assistance device of the present invention.

FIG. 2 illustrates a relationship between a manipulated variable and a supply pressure value in an embodiment example of a respiratory assistance device of the present invention.

[Explanation of symbols]

 1 Gas flow generation unit 2 Conduit 3 Supply pressure target value generation unit 4 Pressure control unit 4a Butterfly valve 4b Stepping motor and controller 5 Flow rate detection unit 6 Pressure detection unit 7 Breathing motivation predicted value calculation unit 8 Operation amount calculation unit A Supply target pressure Value signal B Measured flow rate value signal C Measured pressure value signal D Prediction time specification signal E Predicted value signal of respiratory motivation F Manipulation amount signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Harutomo Waka 3-4-1, Mihara, Ibaraki-shi, Osaka Inside the Osaka Research Center, Teijin Limited issue

Claims (4)

[Claims] 1. A positive airway pressure breathing assistance apparatus, wherein gas flow generation means for generating a gas flow for breathing, conduit means for guiding the gas flow to the airway, and gas pressure supplied to the conduit means for variable pressure in the airway. , A pressure control means for supplying the pressure, a supply pressure target value generating means for generating a pressure target value of the gas flow supplied to the airway, a flow rate detecting means for detecting the gas flow rate in the conduit, and a gas pressure in the conduit. Pressure detection means, first calculation means for predicting the patient's willingness to breathe from the detected flow rate value and pressure value, and calculating the predicted value of the willingness to breathe, and the pressure supplied to the airway is asymptotic to the target supply pressure value. A positive airway-type breathing assistance apparatus comprising: a second calculation means for calculating the operation amount of the pressure control means from the supply pressure target value and the breathing willingness prediction value. 2. The first calculation means uses a value obtained by dividing a square root of a pressure value detected at a certain time by a detected flow rate value as a respiratory willingness prediction value at a certain time. 1. The breathing assistance device according to 1. 3. The respiratory motivation predictive value is calculated as an extrapolated value of a straight line obtained by linearly approximating a past fluctuation transition of the respiratory motivation predictive value. Breathing assistance device. 4. The predicted value as the extrapolated value of a curve obtained as a result of a non-linear approximation using a higher-order function of at least a quadratic value, wherein the first computing means predicts a past fluctuation transition of the breathing willingness value. The respiratory assistance device according to claim 1, which is for calculating.