A flow control method for an electrically controlled flow meter and an anesthesia machine

Abstract

This application provides a flow control method for an electronically controlled flow meter and an anesthesia machine. The method includes: during the entire inspiratory-expiratory cycle, the electronically controlled flow meter only outputs fresh gas during the inspiratory phase; when outputting fresh gas during the inspiratory phase, the shape of its flow waveform is the same as the flow waveform of the inspiratory valve of the respiratory delivery unit. The advantage of this application is that, compared to traditional methods, the time to reach the target pressure or tidal volume is several inspiratory-expiratory cycles faster.

Description

Technical Field

[0001] This application belongs to the field of anesthesia machine technology, specifically relating to a flow control method for an electronically controlled flow meter and an anesthesia machine. Background Technology

[0002] When anesthesia machines are used for ventilation control in clinical settings, a continuous supply of fresh gas is required to the circuit. Doctors can control the flow rate and oxygen concentration entering the circuit by manipulating flow meters. Currently, flow meters can be divided into two main categories: mechanical flow meters and electronically controlled flow meters (ECMs). Mechanical flow meters control the flow rate of the three gases entering the circuit by rotating knobs for oxygen, air, and nitrous oxide. ECMs are more advanced than mechanical flow meters. Doctors can set the target total flow rate and oxygen concentration on the screen. After receiving the control target, the ECM controls solenoid valves and proportional valves to adjust the flow rates of each gas to the target.

[0003] Application scenarios of electronically controlled flow meters, such as Figure 1 As shown, the gas source passes through a proportional valve and an electronically controlled flow meter before entering the circuit. After receiving the target flow rate value, the electronically controlled flow meter controls the flow rates of oxygen, air, and nitrous oxide to reach the expected target, and then mixes with the gas from the intake valve B before entering the circuit.

[0004] In existing anesthesia machines, the system exhausts gas during exhalation, so fresh gas cannot enter the patient's lungs. During inhalation, the pressure in the ventilation circuit increases, which can even lead to poor pressure control. Summary of the Invention

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

[0006] To achieve the above objectives, this application proposes a flow control method for an electronically controlled flow meter, comprising:

[0007] Throughout the entire inspiratory-expiratory cycle, the electronically controlled flow meter only outputs fresh gas during the inspiratory phase;

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

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

[0010]

[0011] Among them, f e This indicates the output flow rate value of the electronically controlled flow meter; t i Indicates the duration of the inhalation phase; V ecmThis indicates the total tidal volume output by the electronically controlled flow meter during the intake phase:

[0012]

[0013] Among them, f ecm This indicates the set flow rate value of the flow meter; f indicates the set inhalation and exhalation frequency.

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

[0015] f e =k*F

[0016] Among them, f e This represents the output flow rate of the electronically controlled flow meter; k represents the tidal volume distribution coefficient.

[0017]

[0018] Among them, f ecm This indicates the set flow rate value of the flow meter; f indicates the set inspiratory and exhalation frequency; P indicates the target pressure; C indicates system compliance;

[0019] F represents the total flow velocity input into the loop by the electronically controlled flow meter:

[0020]

[0021] F1 = P * C / Tslope

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

[0023] This application also provides an anesthesia machine, wherein the anesthesia machine uses the above-described flow control method of the electronically controlled flow meter to control the flow of the electronically controlled flow meter.

[0024] Compared with existing technologies, the advantages of this application are:

[0025] The method provided in this application can achieve the target pressure or tidal volume several inspiratory cycles faster than traditional methods. Attached Figure Description

[0026] Figure 1 The image shows an application scenario for an electronically controlled flow meter.

[0027] Figure 2 The diagram shows the flow control method of an electronically controlled flow meter. Detailed Implementation

[0028] The technical solution of this application will be 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 aforementioned defects arise because the flow rate of existing electronically controlled flowmeters is fixed. That is, after receiving the flow rate value and adjusting it to the target, a constant flow rate is maintained to inflate the circuit during the inhalation and exhalation processes of the anesthesia machine's ventilation control. However, because the system is expelling gas during exhalation, fresh gas cannot enter the patient's lungs. Furthermore, the constant flow rate input during inhalation may affect ventilation control. For example, in pressure-controlled ventilation modes, the overall flow rate waveform input to the circuit is a decelerating wave, meaning the flow rate initially outputs a large value and then gradually decreases until it reaches zero. However, due to the presence of the flowmeter, fresh gas continuously flows into the circuit, leading to pressure increases and excessive pressure control.

[0030] To address the issue that traditional electronically controlled flow meters continuously output a constant flow rate during inhalation and exhalation, which can affect ventilation control, this application provides a flow control method for an electronically controlled flow meter: shifting the fresh gas flow rate during the exhalation phase from the volume control mode and pressure control mode to the inhalation phase, and controlling the flow waveform of the ECM to be the same as the flow waveform of the breathing delivery unit (BDU).

[0031] When the ventilation mode of the anesthesia machine is set to 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 rate:

[0033]

[0034] Where f is the set inhalation and exhalation frequency, f ecm The set flow rate value for the flow meter.

[0035] Step 2: Then calculate the output flow rate of the electronic 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 rate:

[0040]

[0041] Step 2: Calculate the intake tidal volume under the current load condition, 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 velocity input from the electronic flow meter into the loop:

[0046]

[0047] F1 = P * C / Tslope

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

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

[0050] f ecm0 =k*F

[0051] This controls the electronic flow meter to produce the same flow waveform as the BDU section, and the combination of the two completes the pressure control.

[0052] In summary, such as Figure 2 As shown, the flow control method of the electronically controlled flow meter provided in this application is as follows: the fresh gas flow rate, which is normally output at a constant flow rate throughout the entire inspiratory and expiratory cycle, is output only during the inspiratory phase and not during the expiratory phase. Furthermore, when the flow rate is output during the inspiratory phase, its waveform is identical to the flow waveform of the inspiratory valve in the BDU section, ensuring that the flow meter does not affect ventilation control in any mode.

[0053] To achieve capacity and pressure targets, when only real-time flow rate is controlled on the inspiratory valve to achieve the target, the flow rate from the flow meter is essentially an interference to the controller. However, if the real-time flow meter value is considered when designing the controller for tidal volume or pressure, the interference from the flow meter can be predicted in advance, allowing for timely adjustments to the controller and enabling the pressure or tidal volume to reach the target more quickly. Using the method provided in this application, the time to reach the target pressure or tidal volume is several inspiratory-expiratory cycles faster than traditional methods.

[0054] This application also provides an anesthesia machine, in which the flow rate of the electronically controlled flow meter is controlled using the flow control method described above.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application, and should all be covered within the scope of the claims of this application.

Claims

1. An anesthesia machine, characterized in that, The anesthesia machine uses a flow control method for an electrically controlled flow meter to control the flow rate of the flow meter, the method comprising: Throughout the entire inspiratory-expiratory cycle, the electronically controlled flow meter only outputs fresh gas during the inspiratory phase; When fresh gas is delivered during the inhalation phase, the shape of its flow waveform is the same as that of the inhalation valve of the breathing delivery unit. When the ventilation mode of the anesthesia machine is in pressure control mode, the output flow rate of the electronically controlled flow meter is: f e =k*F Among them, f e This represents the output flow rate of the electronically controlled flow meter; k represents the tidal volume distribution coefficient. Among them, f ecm This indicates the set flow rate value of the flow meter; f indicates the set inspiratory and exhalation frequency; P indicates the target pressure; C indicates system compliance; F represents the total flow velocity input into the loop by the electronically controlled flow meter: F1 = P * C / Tslope Where Tslope represents the set pressure rise time; R represents the load air resistance; and t represents the time of the intake phase.

2. The anesthesia machine according to claim 1, characterized in that, When the ventilation mode of the anesthesia machine is in volume control mode, the output flow rate of the electronically controlled flow meter is: Among them, f e This indicates the output flow rate value of the electronically controlled flow meter; t i Indicates the duration of the inhalation phase; V ecm This indicates the total tidal volume output by the electronically controlled flow meter during the intake phase: Among them, f ecm This indicates the set flow rate value of the flow meter; f indicates the set inhalation and exhalation frequency.

Images