A method for adjusting tidal volume based on a second-order large closed loop and an anesthesia machine

Abstract

This application provides a tidal volume adjustment method and an anesthesia machine based on a second-order large closed loop. The method includes: adjusting the tidal volume when the tidal volume change is located in the bias oscillation zone or the arithmetic oscillation zone; obtaining the linear values ​​of the upward and downward adjustment of a proportional valve based on the deviation between the tidal volume and the target value; and adjusting the upward and downward adjustment flow rates based on the linear values ​​of the upward and downward adjustment of the proportional valve. The advantage of this application is that the tidal volume adjustment method based on a second-order large closed loop provided by this application can effectively prevent the tidal volume change from falling into the oscillation zone and can quickly adjust the tidal volume value to the target tidal volume.

Description

Technical Field

[0001] This application belongs to the field of anesthesia machine technology, specifically relating to a tidal volume adjustment method based on a second-order large closed loop and an anesthesia machine. Background Technology

[0002] Tidal volume regulation is an important part of the ventilation function of anesthesia machines. By adjusting the tidal volume, the tidal volume delivered to the patient can be adjusted to the doctor's preset target. When the actual output tidal volume is the same as or close to the doctor's set value, the patient can obtain a better respiratory support effect.

[0003] In general, anesthesia machines use a large closed-loop first-order regulation method to adjust tidal volume. The basic theory behind this method includes:

[0004] At the beginning of inhalation, calculate the difference between the current actual tidal volume and the target tidal volume:

[0005] Δv=v1-v s

[0006] Convert the tidal volume difference above into the flow rate difference during a single inhalation:

[0007]

[0008] Add the flow rate difference to the previous suction flow rate:

[0009] f2=f1+Δf

[0010] Then, during the intake process, the PID algorithm is used to control the output flow of the proportional valve to f2 to complete this adjustment. Because it is only adjusted according to the one-time difference, it is generally called first-order large closed-loop adjustment.

[0011] First-order large closed-loop control methods often lead to tidal volume oscillations during the control process, meaning that the tidal volume value oscillates around the target value and can never converge to the target error band. Summary of the Invention

[0012] The purpose of this application is to overcome the shortcomings of existing tidal volume regulation methods that fall into the oscillation zone.

[0013] To achieve the above objectives, this application proposes a tidal volume adjustment method based on a second-order large closed loop, comprising:

[0014] When the tidal volume change is located in the biased oscillation region or the arithmetic oscillation region, the tidal volume should be adjusted:

[0015] The linear values ​​for adjusting the proportional valve upwards and downwards are obtained based on the deviation between the tidal volume and the target value.

[0016] Adjust the upward and downward flow values ​​according to the linear values ​​of the upward and downward adjustment of the proportional valve.

[0017] As an improvement to the above method, obtaining the linear values ​​for the proportional valve's upward and downward adjustments based on the deviation between the tidal volume and the target value includes:

[0018] Calculate the average values ​​e1 and E2 of the tidal volume error above and below the target value; the average value E1 above is the average of the positive differences between the collected tidal volume values ​​and the target value; the average value E2 below is the average of the negative differences between the collected tidal volume values ​​and the target value.

[0019] Calculate the deviation E of the upper and lower average values. d :

[0020] E d =E1-E2

[0021] Calculate the linearity value k1 of the proportional valve adjustment:

[0022]

[0023] Where Δf1 represents the upward adjustment of the flow rate;

[0024] Calculate the linearity value k2 of the proportional valve's downward adjustment:

[0025]

[0026] Here, Δf2 represents the reduced flow rate value.

[0027] As an improvement to the above method, adjusting the upward and downward flow values ​​based on the linear values ​​of the upward and downward adjustments of the proportional valve includes:

[0028] When adjusting downwards, reduce the flow rate value Δf. d for:

[0029] Δf d =k1*E1

[0030] When adjusting upwards, increase the flow rate value Δf. u for:

[0031] Δf u = -k2*E2.

[0032] As an improvement to the above method, it also includes:

[0033] Determining the stage of tidal volume change includes:

[0034] Using the sliding channel method, record the tidal volume error E = {e1, e2, ..., e} for n ventilations. n}, n>7, calculate the accumulated value E sum The absolute error of the tidal volume of n ventilations is |E| = {|e1|,|e2|,…|e n |};

[0035] When the absolute value of the error |E| is monotonically decreasing and is outside the set error range, it is in the large error convergence region;

[0036] When the absolute value of the error |E| is not monotonic, falls outside the set error range, and the absolute value of the accumulated value |E| sum When the tidal volume is greater than the first set value, it is in the bias oscillation zone;

[0037] When the absolute value of the error |E| is not monotonically decreasing, is outside the set error range, and the absolute value of the accumulated value |E| sum When the tidal volume is less than the second set value, it is in a stable oscillation zone;

[0038] When the absolute value of the error |E| is monotonically decreasing and is within the set error range, it is in the small error convergence region;

[0039] When the absolute value of the error |E| is not monotonically decreasing, and the absolute value of the accumulated value |E| sum When the tidal volume is less than the first tidal volume setting value, it is in the stable region.

[0040] As an improvement to the above method, the first set tidal volume is 1% or 10 ml of the target tidal volume.

[0041] As an improvement to the above method, the second set tidal volume is 2% of the target tidal volume.

[0042] As an improvement to the above method, it also includes:

[0043] When the tidal volume change is located in the large error convergence region, the tidal volume is regulated by the existing first-order large closed-loop regulation or the second-order large closed-loop tidal volume adjustment method.

[0044] This application also provides an anesthesia machine that uses the above-described method to adjust the tidal volume.

[0045] Compared with existing technologies, the advantages of this application are:

[0046] The tidal volume adjustment method based on second-order large closed loop provided in this application can effectively prevent the tidal volume change from falling into the oscillation zone and can quickly adjust the tidal volume value to the target tidal volume. Attached Figure Description

[0047] Figure 1 The diagram shows several stages that may be encountered during tidal volume regulation.

[0048] Figure 2 The diagram shows the tidal volume adjustment method based on a second-order large closed loop. Detailed Implementation

[0049] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0050] like Figure 1 As shown, these are the several stages that may be encountered during the tidal volume regulation process, which can generally be divided into the large error convergence zone, the bias oscillation zone, the arithmetic oscillation zone, the small error convergence zone, and the stable zone.

[0051] Large error convergence region: The tidal volume regulation method starts to operate and can control the tidal volume to converge slightly;

[0052] Biased oscillation zone: The tidal volume fluctuates, and the amplitude of the fluctuations is different and varies greatly.

[0053] Arithmetic oscillation zone: Tidal volume fluctuates, but the amplitude of the fluctuations is almost the same.

[0054] Small error convergence zone: the tidal volume converges to the acceptable error range;

[0055] Stable zone: The tidal volume value remains stable within the acceptable error band.

[0056] Using a first-order large closed-loop control method will definitely reduce the tidal volume error to some extent. However, due to the hysteresis effect of the proportional valve and the inconsistency of each operation of the equipment, the tidal volume regulation may not be able to enter the stable region, but instead get stuck in the bias oscillation region or the arithmetic oscillation region.

[0057] The purpose of this application is to address the problem of potentially falling into two oscillation zones during the regulation of rising tidal volume. Through in-depth research on anesthesia machines, the applicant has discovered that:

[0058] When adjusting the tidal volume, after calculating the current inhalation flow rate f2, due to the control error, hysteresis, and delay of the proportional valve during the inhalation process, it is impossible to output exactly according to the target flow rate. This will eventually lead to a difference between the tidal volume and the target. When this difference is too small, and the proportional valve cannot be adjusted more precisely using this method, the change in tidal volume will fall into the oscillation zone.

[0059] Therefore, more precise adjustment of the proportional valve is the key to solving the oscillation problem. The tidal volume adjustment method based on second-order large closed loop provided in this application divides the entire adjustment process into two parts: process identification and second-order large closed loop adjustment.

[0060] Step 1: Process Identification

[0061] Step 1 is used to identify which stage the current tidal volume regulation is in. It can identify whether it is in the large error regulation area or in the oscillation stage. If it is in the oscillation stage, the second-order large closed-loop regulation function is activated.

[0062] Using the sliding channel method, record the tidal volume error E = {e1, e2…e} for each ventilation. n}, n>7, calculate the accumulated value E sum Calculate its absolute value |E| = {|e1|,|e2|,…|e n |,}

[0063] When the absolute value of the error decreases monotonically and is outside the acceptable error band, it is in the large error convergence region.

[0064] When the absolute value of the error is not monotonic, falls outside the acceptable error band, and the absolute value of the accumulated value is |E sum When the tidal volume exceeds the target tidal volume by 1% or 10ml (whichever is greater), it is in the bias oscillation zone. (1% and 10ml are determined based on the product's allowable error setting).

[0065] When the absolute value of the error is not monotonically decreasing, falls outside the acceptable error band, and the absolute value of the accumulated value is |E sum When the tidal volume is less than 2% of the target tidal volume, it is in a stable oscillation zone.

[0066] When the absolute value of the error decreases monotonically and is within the acceptable error band, it is in the small error convergence region.

[0067] When the absolute value of the error is not monotonically decreasing, and the absolute value of the accumulated value is |E sum When the tidal volume is less than 1% or 10 ml of the target tidal volume, it is in the stable zone.

[0068] Step 2: Second-order large closed-loop regulation

[0069] Based on historical information from the adjustment process, the tidal volume error is combined with the adjustment error to automatically calculate the flow rate that should be output during this inhalation, ensuring that the tidal volume can enter the small error adjustment range and eventually stabilize.

[0070] The reason why the tidal volume change is in the bias oscillation region is basically caused by the hysteresis of the proportional valve. The system needs to adapt to the hysteresis characteristics of the proportional valve, which can be adjusted using the following methods:

[0071] like Figure 2 As shown, the linear characteristics of the proportional valve's upward and downward adjustment in the current flow range are calculated:

[0072] Calculate the average values ​​of the upper and lower deviations of the error respectively.

[0073] Among them, e1, e3, e5, ..., e n-1 All are positive values: e2, e4, e6, ..., e n All are negative values.

[0074] The difference in tidal volume between the two was calculated:

[0075] E d =E1-E2

[0076] Calculate the linearity value of the proportional valve adjustment:

[0077]

[0078] Calculate the linearity of the proportional valve's downward adjustment:

[0079]

[0080] Where Δf1 and Δf2 are the upward and downward adjustment values, respectively. When adjusting downwards in the bias oscillation region, the downward adjustment value is:

[0081] Δf d =k1*E1

[0082] That is, subtract Δf from the previous flow target. d Simply output the result.

[0083] When in the bias oscillation zone, adjust the flow rate upwards as follows:

[0084] Δf u =-k2*E2

[0085] That is, increase Δf based on the previous flow target. u Simply output the result.

[0086] When in the arithmetic oscillation zone, adjust according to the upward or downward adjustment method of the biased oscillation zone.

[0087] When in the large error convergence region, either the existing first-order large closed-loop regulation or the second-order large closed-loop regulation provided in this application can be used.

[0088] This application also provides an anesthesia machine that uses the above-described method to adjust the tidal volume.

[0089] 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 that uses a second-order closed-loop tidal volume adjustment method to regulate tidal volume, the method comprising: When the tidal volume change is located in the biased oscillation region or the arithmetic oscillation region, the tidal volume should be adjusted: The linear values ​​for adjusting the proportional valve upwards and downwards are obtained based on the deviation between the tidal volume and the target value. Adjust the upward and downward flow values ​​according to the linear values ​​of the upward and downward adjustment of the proportional valve; The step of obtaining the linear values ​​for adjusting the proportional valve upwards and downwards based on the deviation between the tidal volume and the target value includes: Calculate the average values ​​E1 and E2 of the tidal volume error above and below the target value; the average value E1 above is the average of the positive differences between the collected tidal volume values ​​and the target value; the average value E2 below is the average of the negative differences between the collected tidal volume values ​​and the target value. Calculate the deviation E of the upper and lower average values. d : THE d =E1-E2 Calculate the linearity value k1 of the proportional valve adjustment: Where Δf1 represents the upward adjustment of the flow rate; Calculate the linearity value k2 of the proportional valve's downward adjustment: Where Δf2 represents the reduced flow rate value; The adjustment of the upward and downward flow values ​​based on the linear values ​​of the upward and downward adjustments of the proportional valve includes: When adjusting downwards, reduce the flow rate value Δf. d for: Δf d =k1*E1 When adjusting upwards, increase the flow rate value Δf. u for: Δf u =-k2*E2。 2. The anesthesia machine according to claim 1, characterized in that, The method further includes: Determining the stage of tidal volume change includes: Using the sliding channel method, record the tidal volume error E = {e1, e2, ..., e} for n ventilations. n }, n>7, calculate the accumulated value E sum The absolute error of the tidal volume of n ventilations is |E| = {|e1|,|e2|,…|e n |}; When the absolute value of the error |E| is monotonically decreasing and is outside the set error range, it is in the large error convergence region; When the absolute value of the error |E| is not monotonic, falls outside the set error range, and the absolute value of the accumulated value |E| sum When the tidal volume is greater than the first set value, it is in the bias oscillation zone; When the absolute value of the error |E| is not monotonically decreasing, is outside the set error range, and the absolute value of the accumulated value |E| sum When the tidal volume is less than the second set value, it is in a stable oscillation zone; When the absolute value of the error |E| is monotonically decreasing and is within the set error range, it is in the small error convergence region; When the absolute value of the error |E| is not monotonically decreasing, and the absolute value of the accumulated value |E| sum When the tidal volume is less than the first tidal volume setting value, it is in the stable region.

3. The anesthesia machine according to claim 2, characterized in that, The first set tidal volume is 1% or 10 ml of the target tidal volume.

4. The anesthesia machine according to claim 2, characterized in that, The second set tidal volume is 2% of the target tidal volume.

5. The anesthesia machine according to claim 1, characterized in that, The method further includes: When the tidal volume change is located in the large error convergence region, the tidal volume is regulated by the existing first-order large closed-loop regulation or the second-order large closed-loop tidal volume adjustment method.

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