Tidal volume adjusting method based on second-order large closed loop and anaesthesia machine

Abstract

The invention provides a tidal volume adjusting method based on a second-order large closed loop and an anaesthesia machine, and the method comprises the steps: adjusting the tidal volume when the change of the tidal volume is in a bias oscillation region or an equal-difference oscillation region: obtaining the up-regulation and down-regulation linear values of a proportional valve according to the deviation between the tidal volume and a target value; and adjusting the up-regulation flow value and the down-regulation flow value according to the up-regulation linear value and the down-regulation linear value of the proportional valve. The tidal volume adjusting method based on the second-order large closed loop has the advantages that the change of the tidal volume can be effectively prevented from falling into an oscillation area, and the value of the tidal volume can be rapidly adjusted to the target tidal volume.

Description

Technical Field

[0001] The present application belongs to the technical field of anesthesia machines, and specifically relates to a tidal volume adjustment method and anesthesia machine based on a second-order large closed loop. Background Art

[0002] Tidal volume regulation is an important part of the ventilation function of the anesthesia machine. 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 value set by the doctor, the patient can get better respiratory support effect.

[0003] Generally, a large closed-loop first-order regulation method is used in anesthesia machines to adjust the tidal volume. The general theory of this method includes:

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

[0005] Δv=v1-v s

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

[0007]

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

[0009] f2=f1+Δf

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

[0011] The first-order large closed-loop regulation method often leads to tidal volume oscillation during the regulation process, that is, the tidal volume value oscillates above and below the target value and can never converge to the target error band. Summary of the invention

[0012] The purpose of the present application is to overcome the defect that the existing tidal volume adjustment method may fall into the oscillation zone.

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

[0014] When the tidal volume changes in the bias oscillation zone or the arithmetic difference oscillation zone, adjust the tidal volume:

[0015] The linear value of the proportional valve upward and downward adjustment is obtained according to the deviation between the tidal volume and the target value;

[0016] The upward and downward flow values ​​are adjusted according to the upward and downward linear values ​​of the proportional valve.

[0017] As an improvement of the above method, the method of obtaining the linear value of the proportional valve upward and downward adjustment according to the deviation between the tidal volume and the target value includes:

[0018] Calculate the upper and lower average values ​​e1 and E2 of the error between the tidal volume and the target value; the upper average value E1 is the average value of the values ​​of the multiple tidal volume values ​​collected with positive differences from the target value; the lower average value E2 is the average value of the values ​​of the multiple tidal volume values ​​collected with negative differences from the target value;

[0019] Calculate the deviation E above and below the mean d :

[0020] E d =E1-E2

[0021] Calculate the linear value k1 of the proportional valve increase:

[0022]

[0023] Among them, Δf1 represents the upward flow value;

[0024] Calculate the linear value k2 of the proportional valve down adjustment:

[0025]

[0026] Among them, Δf2 represents the downward adjustment flow value.

[0027] As an improvement of the above method, the adjusting the flow value of upward and downward adjustment according to the linear value of upward and downward adjustment of the proportional valve includes:

[0028] When adjusting downward, adjust the flow value Δf downward d for:

[0029] Δf d =k1*E1

[0030] When adjusting upward, increase the flow value Δf u for:

[0031] Δf u =-k2*E2.

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

[0033] Determine the stage of tidal volume change, including:

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

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

[0036] When the absolute value of the error |E| is non-monotonic and 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 tidal volume, it is in the bias oscillation zone;

[0037] When the absolute value of the error |E| is non-monotonically decreasing and 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 the stable oscillation zone;

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

[0039] When the absolute value of the error |E| is non-monotonically decreasing, and the absolute value of the accumulated value |E sum When it is less than the first tidal volume setting value, it is in the stable zone.

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

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

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

[0043] When the tidal volume change is in the large error convergence area, the tidal volume is adjusted using the existing first-order large closed-loop regulation or the second-order large closed-loop tidal volume adjustment method.

[0044] The present application also provides an anesthesia machine, which uses the above method to adjust the tidal volume.

[0045] Compared with the prior art, the advantages of this application are:

[0046] The tidal volume adjustment method based on a second-order large closed loop provided in the present application can effectively prevent the change of tidal volume from falling into an oscillation zone, and can quickly adjust the value of the tidal volume to the target tidal volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Shown are several stages that may be encountered during tidal volume regulation;

[0048] Figure 2 Shown is a flow chart of the tidal volume adjustment method based on a second-order large closed loop. DETAILED DESCRIPTION

[0049] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

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

[0051] Large error convergence area: the tidal volume adjustment method starts to run and can control the tidal volume to converge slightly;

[0052] Bias oscillation area: the tidal volume fluctuates, and the amplitudes of the up and down fluctuations are different and vary greatly;

[0053] Arithmetic oscillation zone: the tidal volume fluctuates, but the amplitude of the up and down fluctuations is almost the same;

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

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

[0056] Among them, the use of a first-order large closed-loop regulation method will definitely reduce the tidal volume error a little, but due to the hysteresis effect of the proportional valve, the inconsistency of the equipment's operation each time, etc., the tidal volume regulation may not be able to enter the stable zone, but may be stuck in the bias oscillation zone or the arithmetic difference oscillation zone.

[0057] The purpose of this application is to solve the problem that during the adjustment of the rising tidal volume, two oscillation zones may occur. Through in-depth research on anesthesia machines, the applicant found that:

[0058] When adjusting the tidal volume, after calculating the inspiratory flow rate f2, it is impossible to output completely according to the target flow rate due to the control error, hysteresis, delay and other characteristics of the proportional valve during the inhalation process, which 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 finely using this method, the change in tidal volume will fall into the oscillation zone.

[0059] Therefore, more detailed adjustment of the proportional valve is the key to solving the oscillation problem. The tidal volume adjustment method based on the 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 the stage of the current tidal volume regulation. It can be identified whether it is currently in a large error regulation area or in an oscillation stage. If it is in the oscillation stage, the second-order large closed-loop regulation function is started.

[0062] Using the sliding channel method, the tidal volume error E = {e1, e2…e n}, n>7, calculate the cumulative 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 qualified error band, it is in the large error convergence zone.

[0064] When the absolute value of the error is non-monotonic, it is outside the qualified error band, and the absolute value of the accumulated value |E sum |When it is greater than the target tidal volume by 1% or 10ml (the maximum value), it is in the bias oscillation zone. (1% and 10ml are determined by the allowable error set by the product).

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

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

[0067] When the absolute value of the error is non-monotonically decreasing and the absolute value of the accumulated value |E sum When it is less than 1% or 10ml of the target tidal volume, it is in the stable zone.

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

[0069] According to the historical information of the regulation process, the tidal volume error is combined with the error of the adjustment error to automatically calculate the flow rate that should be output for this inhalation to ensure that the tidal volume can enter the small error regulation area and finally stabilize.

[0070] The reason why the change of tidal volume is in the bias oscillation zone is basically caused by the hysteresis of the proportional valve. The system needs to adapt to the characteristics of the hysteresis of the proportional valve. The following methods can be used for adjustment:

[0071] like Figure 2 As shown, the linear characteristics of the proportional valve in the current flow range are calculated:

[0072] Calculate the average of the upper and lower errors respectively

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

[0074] Calculate the deviation of the tidal volumes:

[0075] E d =E1-E2

[0076] Calculate the linear value of proportional valve increase:

[0077]

[0078] Calculate the linear value of proportional valve down regulation:

[0079]

[0080] Among them, Δf1 and Δf2 are the flow rate values ​​for upward adjustment and downward adjustment respectively. When in the bias oscillation area, the flow rate value for downward adjustment is:

[0081] Δf d =k1*E1

[0082] That is, subtract Δf from the last flow target. d Just output it.

[0083] When in the bias oscillation zone, the flow rate is adjusted upwards to:

[0084] Δf u =-k2*E2

[0085] That is, add Δf based on the last flow target u Just output it.

[0086] When it is in the equal-difference oscillation zone, it can be adjusted in the same way as the upward or downward adjustment in the bias 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 the present application can be adopted.

[0088] The present application also provides an anesthesia machine, which uses the above method to adjust the tidal volume.

[0089] 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 tidal volume adjustment method based on a second-order large closed loop, comprising: When the tidal volume changes in the bias oscillation zone or the arithmetic difference oscillation zone, adjust the tidal volume: The linear value of the proportional valve upward and downward adjustment is obtained according to the deviation between the tidal volume and the target value; The upward and downward flow values ​​are adjusted according to the upward and downward linear values ​​of the proportional valve.

2. The tidal volume adjustment method based on a second-order large closed loop according to claim 1, characterized in that: The method of obtaining the linear value of the proportional valve upward and downward adjustment according to the deviation between the tidal volume and the target value includes: Calculate the upper and lower average values ​​E1 and E2 of the error between the tidal volume and the target value; the upper average value E1 is the average value of the values ​​of the multiple tidal volume values ​​collected with positive differences from the target value; the lower average value E2 is the average value of the values ​​of the multiple tidal volume values ​​collected with negative differences from the target value; Calculate the deviation E above and below the mean d : THE d =E1-E2 Calculate the linear value k1 of the proportional valve increase: Among them, Δf1 represents the upward flow value; Calculate the linear value k2 of the proportional valve down adjustment: Among them, Δf2 represents the downward adjustment flow value.

3. The tidal volume adjustment method based on a second-order large closed loop according to claim 3, characterized in that: The step of adjusting the flow value up and down according to the linear value of the proportional valve up and down comprises: When adjusting downward, adjust the flow value Δf downward d for: Δf d =k1*E1 When adjusting upward, increase the flow value Δf u for: Δf u =-k2*E2。 4. The tidal volume adjustment method based on a second-order large closed loop according to claim 1, characterized in that: Also includes: Determine the stage of tidal volume change, including: Using the sliding channel method, record the tidal volume error E = {e1, e2…e n }, n>7, calculate the cumulative value E sum The absolute value of the error between the tidal volume of n ventilations |E| = {|e1|,|e2|,…|e n |}; When the absolute value of the error |E| decreases monotonically and is outside the set error range, it is in the large error convergence zone; When the absolute value of the error |E| is non-monotonic and 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 tidal volume, it is in the bias oscillation zone; When the absolute value of the error |E| is non-monotonically decreasing and 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 the stable oscillation zone; When the absolute value of the error |E| decreases monotonically and is within the set error range, it is in the small error convergence zone; When the absolute value of the error |E| is non-monotonically decreasing, and the absolute value of the accumulated value |E sum When it is less than the first tidal volume setting value, it is in the stable zone.

5. The tidal volume adjustment method based on a second-order large closed loop according to claim 4, characterized in that: The first set tidal volume is 1% of the target tidal volume or 10 ml.

6. The tidal volume adjustment method based on a second-order large closed loop according to claim 4, characterized in that: The second set tidal volume is 2% of the target tidal volume.

7. The tidal volume adjustment method based on a second-order large closed loop according to any one of claims 1 to 3, characterized in that: Also includes: When the tidal volume change is in the large error convergence area, the tidal volume is adjusted using the existing first-order large closed-loop regulation or the second-order large closed-loop tidal volume adjustment method.

8. An anesthesia machine, characterized in that: The anesthesia machine adjusts the tidal volume using the method described in any one of claims 1-7.

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