Flow control method of electric control flow meter and anaesthesia machine

Abstract

The invention provides a flow control method of an electric control flow meter and an anaesthesia machine, and the method comprises the following steps: during the whole inspiration and expiration period, the electric control flow meter outputs fresh gas only in the inspiration stage; when fresh air is output in the inspiration stage, the flow waveform of the fresh air is the same as that of the inspiration valve of the breathing conveying unit. The method has the advantages that compared with a traditional method, the time that the pressure or the tidal volume reaches the target value can be shortened by several inspiration and expiration periods.

Description

Technical Field

[0001] The present application belongs to the technical field of anesthesia machines, and specifically relates to a flow control method of an electronically controlled flow meter and an anesthesia machine. Background Art

[0002] When the anesthesia machine implements the ventilation control function in clinical practice, it needs to continuously add fresh gas to the circuit. Doctors can control the flow rate and oxygen concentration entering the circuit by controlling the flow meter. At present, flow meters can be divided into two categories: mechanical flow meters and electronically controlled flow meters (ECM). Mechanical flow meters control the flow of three gases entering the circuit by rotating the knobs of oxygen, air, and nitrous oxide in the flow meter; ECM is more advanced than mechanical flow meters. Doctors can set the target total flow rate and oxygen concentration value on the screen, and then after receiving the control target, ECM controls the solenoid valve and proportional valve to adjust the flow of each channel to the target.

[0003] Application scenarios of electronic flowmeters such as Figure 1 As shown, the gas source passes through the proportional valve and the electronically controlled flow meter and then enters the loop. After receiving the target flow value, the electronically controlled flow meter controls the flow of oxygen, air, and nitrous oxide to reach the expected target, and then mixes with the gas in the B path of the inhalation valve and enters the loop.

[0004] In existing anesthesia machines, the system exhausts air outward during exhalation, so fresh gas cannot enter the patient's lungs. During inhalation, the pressure in the ventilation circuit will increase, and even cause pressure control to exceed the tolerance. Summary of the invention

[0005] The purpose of the present application is to overcome the defect of excessive pressure difference in the ventilation circuit during inspiration in the prior art.

[0006] In order to achieve the above object, the present application proposes a flow control method of an electronically controlled flow meter, comprising:

[0007] During the entire breathing cycle, the electronically controlled flow meter outputs fresh gas only during the inspiration phase;

[0008] When fresh gas is output during the inspiration phase, the shape of its flow waveform is the same as the flow waveform of the inspiration valve of the breathing delivery unit.

[0009] As an improvement of the above method, when the control mode of the ventilation mode of the anesthesia machine is the volume control mode, the output flow value of the electronically controlled flow meter is:

[0010]

[0011] Among them, f e Indicates the output flow value of the electronically controlled flowmeter; t i Indicates the duration of the inspiratory phase; V ecmIndicates the total tidal volume output by the electronically controlled flow meter during the inspiratory phase:

[0012]

[0013] Among them, f ecm represents the set flow value of the flow meter; f represents the set breathing frequency.

[0014] As an improvement of the above method, when the control mode of the ventilation mode of the anesthesia machine is the pressure control mode, the output flow value of the electronically controlled flow meter is:

[0015] f e = k * F

[0016] Among them, f e It represents the output flow value of the electronically controlled flow meter; k represents the tidal volume distribution coefficient:

[0017]

[0018] Among them, f ecm Indicates the set flow meter flow value; f indicates the set breathing frequency; P indicates the target pressure; C indicates the system compliance;

[0019] F represents the total flow rate input into the loop by the electronically controlled flowmeter:

[0020]

[0021] F1=P*C / Tslope

[0022] Wherein, Tslope represents the set pressure rise time; R represents the load air resistance; and t represents the time of the inhalation phase.

[0023] The present application also provides an anesthesia machine, which uses the above-mentioned flow control method of the electronically controlled flow meter to control the flow of the electronically controlled flow meter.

[0024] Compared with the prior art, the advantages of this application are:

[0025] By using the method provided in the present application, the time for the pressure or tidal volume to reach the target value can be several respiratory cycles faster than that of the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The following are application scenarios of electronically controlled flow meters;

[0027] Figure 2 Shown is a flow chart of the flow control method of the electronically controlled flow meter. DETAILED DESCRIPTION

[0028] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0029] Through in-depth research on the ventilation control of existing anesthesia machines, the applicant discovered that the reason for the above-mentioned defects is that the flow rate of the existing electronically controlled flowmeter is fixed, that is, after receiving the flow value and adjusting it to the target, a constant flow is maintained to inflate the circuit during the inhalation and exhalation process of the ventilation control of the anesthesia machine. However, because the system is exhausting air to the outside during exhalation, fresh gas cannot enter the patient's lungs. In addition, the constant flow input during inhalation may have an impact on ventilation control. For example, in the ventilation mode of the pressure control mode, the overall flow waveform input into the circuit is a deceleration wave, that is, the flow rate first outputs a large value and then slowly decreases, and gradually shrinks to zero. However, due to the presence of the flowmeter, fresh gas continues to flow into the circuit, which will cause the pressure to rise and the pressure control to exceed the tolerance.

[0030] In order to solve the problem that traditional electronically controlled flow meters always output a constant flow during inhalation and exhalation, which affects ventilation control, the present application provides a flow control method for an electronically controlled flow meter: the fresh gas flow in the exhalation phase in the volume control mode and the pressure control mode is moved to the inhalation phase, and the flow waveform of the ECM is controlled to be the same as the flow waveform of the breathing delivery unit (BDU).

[0031] When the ventilation mode of the anesthesia machine is volume control mode:

[0032] Step 1: Calculate the total tidal volume output by the ECM during the inspiratory phase based on the ventilation frequency and set flow value:

[0033]

[0034] Among them, f is the set breathing frequency, f ecm is the set flow meter flow value.

[0035] Step 2: Then calculate the output flow value of the electronically controlled flow meter:

[0036]

[0037] Among them, t i Indicates the duration of the inhalation phase.

[0038] When the ventilation mode of the anesthesia machine is in pressure control mode:

[0039] Step 1: Calculate the total tidal volume output by the ECM during the inspiratory phase based on the ventilation frequency and set flow value:

[0040]

[0041] Step 2: Calculate the inspiratory tidal volume under the current load, where P is the target pressure and C is the system compliance:

[0042] V=P*C

[0043] Step 3: Calculate the tidal volume distribution coefficient:

[0044]

[0045] Step 4: Calculate the total flow rate of the electronic flow meter input into the loop:

[0046]

[0047] F1=P*C / Tslope

[0048] Among them, Tslope represents the set pressure rise time, which is set by the host computer; t represents the time of the inhalation phase; R represents the load (patient) air resistance, which is monitored by the anesthesia machine like compliance.

[0049] Step 5: Calculate the output flow of the electronically controlled flow meter as:

[0050] f ecm0 = k * F

[0051] In this way, the electronically controlled flow meter is controlled to produce the same flow waveform as the BDU part, and the combination of the two can just complete the pressure control.

[0052] In summary, if Figure 2 As shown, the flow control method of the electronically controlled flow meter provided in the present application is: the fresh gas flow rate originally output by the flow meter at a constant flow rate during the entire breathing cycle is outputted in the inhalation phase, and not in the exhalation phase. When the flow rate is outputted in the inhalation phase, the shape of its flow waveform is equal to the flow waveform of the inhalation valve of the BDU part, ensuring that the flow meter will not affect the ventilation control in any mode.

[0053] In order to achieve the volume target and pressure target, when the inhalation valve is controlled in real time only based on the real-time flow, the flow of the flow meter is equivalent to interference to the controller. If the real-time flow meter value is considered when designing the tidal volume or pressure controller, the interference of the flow meter on the control can be predicted in advance, and the controller can be adjusted in advance to make the pressure or tidal volume reach the target faster. The method provided by this application can make the time for the pressure or tidal volume to reach the target value faster by several respiratory cycles compared with the traditional method.

[0054] The present application also provides an anesthesia machine, which uses the flow control method of the above-mentioned electronically controlled flow meter to control the flow of the electronically controlled flow meter.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A flow control method for an electronically controlled flow meter, comprising: During the entire breathing cycle, the electronically controlled flow meter outputs fresh gas only during the inspiration phase; When fresh gas is output during the inspiration phase, the shape of its flow waveform is the same as the flow waveform of the inspiration valve of the breathing delivery unit.

2. The flow control method of the electronically controlled flow meter according to claim 1 comprises: When the ventilation mode of the anesthesia machine is controlled in volume control mode, the output flow value of the electronically controlled flow meter is: Among them, f e Indicates the output flow value of the electronically controlled flowmeter; t i Indicates the duration of the inspiratory phase; V ecm Indicates the total tidal volume output by the electronically controlled flow meter during the inspiratory phase: Among them, f ecm represents the set flow value of the flow meter; f represents the set breathing frequency.

3. The flow control method of the electronically controlled flow meter according to claim 1 comprises: When the ventilation mode of the anesthesia machine is in pressure control mode, the output flow value of the electronically controlled flow meter is: f e =k*F Among them, f e It represents the output flow value of the electronically controlled flow meter; k represents the tidal volume distribution coefficient: Among them, f ecm Indicates the set flow meter flow value; f indicates the set breathing frequency; P indicates the target pressure; C indicates the system compliance; F represents the total flow rate input into the loop by the electronic flowmeter: F1=P*C / Tslope Wherein, Tslope represents the set pressure rise time; R represents the load air resistance; and t represents the time of the inhalation phase.

4. An anesthesia machine, characterized in that: The anesthesia machine uses the flow control method of the electronically controlled flow meter described in any one of claims 1 to 3 to control the flow of the electronically controlled flow meter.

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