A tidal volume detection method and corresponding device for a bilevel ventilator

Abstract

The present invention relates to the technical field of ventilators, and discloses a tidal volume detection method and a corresponding device for a bilevel ventilator. The tidal volume detection method includes: obtaining the target pressure of the ventilator and the real-time instantaneous flow rate value of the ventilator; obtaining the basic flow rate of the ventilator under the target pressure; obtaining the time threshold for the inspiratory phase and the time threshold for the expiratory phase; obtaining the flow rate difference between the instantaneous flow rate and the basic flow rate during the inspiratory phase and the expiratory phase; performing an integration operation based on the flow rate difference and the time threshold to obtain the inspiratory tidal volume and the expiratory tidal volume; calculating based on the difference between the slope of the flow rate curve generated by the instantaneous flow rate, the time threshold, and the tidal volume to obtain the new basic flow rates for the inspiratory phase and the expiratory phase. The present invention avoids the problem that existing ventilators ignore the influence of the basic flow rates in the inspiratory phase and the expiratory phase, resulting in a large error in tidal volume detection, improves the detection accuracy of the tidal volume of the ventilator, and enables the ventilator to automatically adjust the basic flow rates in the inspiratory phase and the expiratory phase.

Description

Technical Field

[0001] The present invention relates to the technical field of ventilators, and particularly to the tidal volume detection of a bilevel ventilator. Background Art

[0002] A ventilator is a crucial medical device that can prevent and treat respiratory failure, reduce complications, improve the ventilation and gas exchange functions of patients, and save and extend the lives of patients. Especially during the treatment of lung-related diseases, the role of the ventilator is almost irreplaceable.

[0003] As is known to those skilled in the art, compared with a single-level ventilator that can only provide one airway positive pressure, a bilevel ventilator can provide two different airway positive pressures for patients. When the patient inhales, a higher pressure is provided to facilitate inhalation, and when the patient exhales, a lower pressure is provided to ensure smooth breathing of the patient, which can provide better comfort and treatment effects for the patient. The bilevel ventilator has multiple adjustable working parameters, mainly including tidal volume, pressure, flow rate, respiratory frequency, etc. Among them, the tidal volume refers to the volume of gas inhaled or exhaled by a person each time.

[0004] Currently, the ventilation modes of ventilators mainly include pressure control ventilation mode and volume control mode. Pressure control is that the ventilator manages ventilation with a preset airway pressure, and the tidal volume is mainly determined by the difference between the airway pressure and the positive end-expiratory pressure, the inspiratory time, and the airway resistance and thoracic and lung compliance of the patient. Volume control is to manage ventilation with a preset ventilation volume to keep the tidal volume constant, and the size of the tidal volume is determined by the minute exhaled ventilation volume, the ventilation frequency, or the minute inspiratory flow rate and the inspiratory time. Medical staff will adjust the pressure support of the device for the patient based on information such as the tidal volume, real-time respiratory frequency, and minute ventilation volume of the patient when using the ventilator, so as to achieve the best treatment effect for the patient. And no matter which control method of the ventilation mode, the tidal volume needs to be detected and confirmed.

[0005] Currently, the commonly used tidal volume detection and calculation methods in dual-level ventilators mainly follow the tidal volume calculation principle of single-level ventilators. Taking the patent CN 110975089A as an example, it mainly calculates the difference between a basic flow rate and an instantaneous flow rate, and then integrates to obtain the inspiratory tidal volume and expiratory tidal volume; a single-level ventilator only outputs one treatment pressure, while a dual-level ventilator outputs two treatment pressures, namely the inspiratory output pressure and the expiratory output pressure, and quickly switches the pressure according to the PID algorithm. The existing tidal volume mainly ignores the influence of the inspiratory output air pressure and the expiratory output air pressure. After the ventilator detects an inspiratory action, it will quickly switch the pressure from the expiratory pressure to the inspiratory pressure. Therefore, the subsequent instantaneous flow rate in the pipeline during inspiration changes based on the inspiratory phase basic flow rate, and the principle is the same when exhaling and switching to inhaling; so the gas volume between the inspiratory pressure and the expiratory pressure should not be considered within the scope of tidal volume calculation, otherwise it will lead to a large error in the calculated tidal volume. At the same time, during the use of the ventilator, there will also be non-intentional air leakage such as mask loosening, which will also cause the tidal volume detection to be distorted. Therefore, there is an urgent need for a more accurate tidal volume detection method to improve the tidal volume detection accuracy, thereby improving the treatment effect of dual-level ventilators. Summary of the Invention

[0006] The main objective of the present invention is to provide a tidal volume detection method and corresponding device for a dual-level ventilator, aiming to solve the technical problem that the existing tidal volume detection method ignores the influence of the inspiratory phase basic flow and the expiratory phase basic flow of the dual-level ventilator, resulting in a large error in the detected tidal volume.

[0007] To achieve the above objective, the present invention provides a tidal volume detection method, including the following steps:

[0008] Step 1: Obtain the target pressure of the ventilator, and collect the instantaneous flow rate F of the ventilator in real time at time intervals Δt, and perform moving average filtering on the instantaneous flow rate.

[0009] Step 2: Obtain the basic flow rates L 1 and L 2 of the inspiratory phase and the expiratory phase of the ventilator according to the target pressure;

[0010] Step 3: Obtain the moment when the instantaneous flow rate F is equal to the inspiratory phase basic flow rate L 1 , and the moment when the instantaneous flow rate F is equal to the expiratory phase basic flow rate L 2 , to obtain the inspiratory phase time threshold t i and the expiratory phase time threshold t e ;

[0011] Step 4: Calculate the flow rate difference F 1 between the instantaneous flow rate F and the inspiratory phase basic flow rate L 1, the difference F between the instantaneous flow rate F and the expiratory baseline flow rate L during the expiratory phase 2 ; 2 ;

[0012] Step 5: Perform an integration operation based on the inspiratory time threshold t 1 and the flow rate difference F 1 to obtain the inspiratory tidal volume V i . Perform an integration operation between the expiratory time threshold t 2 and the flow rate difference F 2 to obtain the expiratory tidal volume V e .

[0013] It is well known in the art that the target pressure of the ventilator is designed to be set by the user according to personal circumstances.

[0014] Preferably, the tidal volume detection method of the ventilator further includes Step 6: Adjust the inspiratory and expiratory baseline flow rates L i and L e according to V 1 and V 2 to correct the tidal volume detection error.

[0015] Preferably, the step of obtaining the inspiratory and expiratory baseline flow rates L 1 and L 2 in Step 2 includes:

[0016] Obtain the target pressure;

[0017] Obtain the corresponding baseline flow rate according to the target pressure.

[0018] Preferably, the step of adjusting the inspiratory and expiratory baseline flow rates L i and L e according to V 1 and V 2 in Step 6 includes:

[0019] Extract the slope θ 1 of the flow rate curve at the intersection of the flow rate curve generated according to the instantaneous flow rate and the inspiratory baseline flow rate curve, 2 as well as the slope θ 3 of the flow rate curve at the intersection with the expiratory baseline flow rate curve, 4 ;

[0020] Calculate the average error between the inspiratory tidal volume and the expiratory tidal volume

[0021] When the inspiratory tidal volume V i is greater than the expiratory tidal volume V e :

[0022] The calibration factor of the inspiratory baseline flow rate L 1 is The updated inspiratory baseline flow rate is L 1 +MQ 1 ;

[0023] The expiratory baseline flow rate L 2 The calibration factor of The updated expiratory baseline flow rate is L 2 +MQ 2 ;

[0024] When the inspiratory tidal volume V i is less than the expiratory tidal volume V e :

[0025] The calibration factor of the inspiratory baseline flow rate L 1 is The updated inspiratory baseline flow rate is L 1 -MQ 3 ;

[0026] The expiratory baseline flow rate L 2 The calibration factor of The updated expiratory baseline flow rate is L 2 -MQ 4 ;

[0027] In addition, to achieve the above object, the present invention also provides a tidal volume detection device, and the tidal volume detection device of the ventilator includes:

[0028] A ventilator data acquisition module that acquires the target pressure of the ventilator and the instantaneous flow rate value of the ventilator in real time;

[0029] A baseline flow rate acquisition module for acquiring the baseline flow rate under the target pressure;

[0030] A time threshold acquisition module for acquiring the time threshold of the inspiratory phase and the time threshold of the expiratory phase;

[0031] A flow rate difference acquisition module for acquiring the flow rate difference between the instantaneous flow rate and the inspiratory baseline flow rate during the inspiratory phase, and the difference between the instantaneous flow rate and the expiratory baseline flow rate during the expiratory phase;

[0032] A tidal volume calculation module for performing integral operation according to the flow rate difference and the time threshold to obtain the inspiratory tidal volume and the expiratory tidal volume;

[0033] Preferably, the above tidal volume detection device further includes a baseline flow rate calibration module, which calculates and obtains the new inspiratory and expiratory baseline flow rates according to the slope of the flow rate curve generated by the instantaneous flow rate, the time threshold, and the difference between the tidal volumes.

[0034] The present invention comprehensively considers the influence of the inspiratory basic flow rate and the expiratory basic flow rate on the tidal volume. In a bilevel ventilator, the inspiratory and expiratory conversion processes are completed instantaneously. According to the regulation of the PID algorithm, the instantaneous airflow will quickly switch between the inspiratory and expiratory basic flow rates. Therefore, the gas volume between the basic flow rates should not be included in the calculation of the tidal volume, and the calculated tidal volume will be more accurate, helping to adjust the pressure support of the ventilator device for the patient to achieve the best treatment effect. At the same time, the basic flow rate of each updated respiratory phase is also an important parameter that can play a decisive role in the ventilator's respiratory trigger and weaning algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flowchart of a method for detecting tidal volume of a ventilator according to the present invention;

[0036] Figure 2 is a schematic diagram of the principle of a device for detecting tidal volume of a ventilator according to the present invention;

[0037] Figure 3 is a schematic diagram of the principle of a device for detecting tidal volume of a ventilator according to the present invention;

[0038] Figure 4 is a schematic diagram of the functional modules of a device for detecting tidal volume of a ventilator according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] As Figure 1 shown, the present invention provides a method for detecting tidal volume for a bilevel ventilator, which includes the following steps: Step 1 (S100): Obtain the target pressure of the ventilator, and collect the instantaneous flow rate F of the ventilator in real time at time intervals Δt, and perform moving average filtering on the instantaneous flow rate; Step 2 (S200): Obtain the basic flow rates Lin and Lout of the inspiratory and expiratory phases of the ventilator according to the target pressure 1 and Lout 2 ; Step 3 (S300): Obtain the moment when the instantaneous flow rate F is equal to the inspiratory basic flow rate Lin 1 , and the moment when the instantaneous flow rate F is equal to the expiratory basic flow rate Lout 2 , to obtain the inspiratory phase time threshold tin i and the expiratory phase time threshold tout e ; Step 4 (S400): Calculate the flow rate difference ΔF between the instantaneous flow rate F and the inspiratory basic flow rate Lin during the inspiratory phase 1 , and the flow rate difference ΔF between the instantaneous flow rate F and the expiratory basic flow rate Lout during the expiratory phase 1 ,2 the difference value F 2 ; Step 5 (S500): According to the inhalation phase time threshold t 1 and the flow rate difference value F 1 perform an integration operation to obtain the inhalation tidal volume V i , and according to the exhalation phase time threshold t 2 and the flow rate difference value F 2 perform an integration operation therebetween to obtain the exhalation tidal volume V e .

[0041] The step of obtaining the basic flow rates L 1 and L 2 of the inhalation phase and the exhalation phase of the ventilator in the second step includes: obtaining the target pressure; obtaining the corresponding basic flow rate according to the target pressure.

[0042] During the use of the ventilator, when the patient wears the face mask to breathe, the gas flow rate at a certain moment in the breathing pipeline is the instantaneous flow rate, while the basic flow rate refers to the gas flow rate in the pipeline when wearing the face mask without breathing. Since the turbine drive of each ventilator product and the gas path design in the ventilator are different, the basic flow rate is different.

[0043] As mentioned above, the bilevel ventilator provides bilevel pressure support during use. When the patient inhales, the ventilator provides a higher pressure to facilitate inhalation. When the patient exhales, a lower pressure is provided to ensure smooth breathing of the patient.

[0044] As Figure 2 shown, when the patient's respiratory airflow velocity is above the zero line, it is the inhalation phase, and when it is below the zero line, it is the exhalation phase. When the support pressure provided by the ventilator is large, the instantaneous flow rate F is higher than the original inhalation phase basic flow rate, and the user is in the inhalation phase, where the instantaneous flow rate F is composed of the user's spontaneous inhalation airflow velocity and the inhalation airflow velocity generated by the ventilator. When the support pressure provided by the ventilator is small, the direction of the airflow velocity is reversed, the value of the instantaneous flow rate F decreases, and is lower than the original exhalation phase basic flow rate, and the user is in the exhalation phase.

[0045] During the use of the ventilator, in order to ensure that the patient can discharge the CO2 generated during breathing in the pipeline when wearing the face mask for treatment, the breathing face mask is provided with air leakage holes. Therefore, the ventilator has intentional air leakage, and the basic flow rates of both the inhalation phase and the exhalation phase are greater than zero. For the same patient, when the face mask is worn normally, the inhalation tidal volume and the exhalation tidal volume of one breath are basically equal, that is Figure 2 the shaded area of the inhalation phase and the shaded area of the exhalation phase in

[0046] If the mask becomes loose, resulting in an increase in unintentional air leakage, at this time, the calculation of tidal volume still uses the original inspiratory baseline flow rate and the original expiratory baseline flow rate as the standard air leakage value. The situation where the original inspiratory tidal volume is equal to the expiratory tidal volume changes to the inspiratory tidal volume being much larger than the expiratory tidal volume, which will cause a calculation error in the patient's inspiratory tidal volume value and expiratory tidal volume value. Therefore, after the occurrence of unintentional air leakage, the baseline flow rate should be increased on the original basis, as Figure 2 shown, the position of the new baseline flow rate line moves upward.

[0047] If the mask is correctly re-worn, at this time, the calculation of tidal volume still uses the original inspiratory baseline flow rate and the original expiratory baseline flow rate as the standard air leakage value. The situation where the original inspiratory tidal volume is equal to the expiratory tidal volume changes to the inspiratory tidal volume being much smaller than the expiratory tidal volume, which will cause a calculation error in the patient's inspiratory tidal volume value and expiratory tidal volume value. Therefore, after the air leakage returns to normal, the baseline flow rate should be decreased on the original basis, as Figure 3 shown, the position of the new baseline flow rate line moves downward.

[0048] Furthermore, the above-mentioned ventilator tidal volume detection method further includes step six (S600): Adjust the inspiratory and expiratory baseline flow rates L i and L e according to V 1 and V 2 , including:

[0049] Extract the slope θ 1 、θ 2 of the flow rate curve at the intersection point of the flow rate curve generated according to the instantaneous flow rate and the inspiratory baseline flow rate curve, and the slope θ 3 、θ 4 at the intersection point with the expiratory baseline flow rate curve;

[0050] If the unintentional air leakage suddenly increases during the use of the ventilator, in order to keep the pressure level at the mask end unchanged, the ventilator will compensate for the pressure according to the air leakage situation and provide higher pressure support. At this time, the baseline flow rate will increase. When calculating the tidal volume based on the original baseline flow rate, the inspiratory tidal volume is greater than the expiratory tidal volume, and the average error

[0051] between the inspiratory tidal volume and the expiratory tidal volume is calculated. The calibration factor of the inspiratory baseline flow rate L 1 is The updated inspiratory baseline flow rate is L 1 +MQ 1 ;

[0052] The calibration factor of the expiratory baseline flow rate L 2 is The updated expiratory baseline flow rate is L 2 +MQ2 ;

[0053] The inspiratory baseline flow rate and the expiratory baseline flow rate remain stable until the inspiratory tidal volume and the expiratory tidal volume return to being equal again.

[0054] If the unintentional leakage of the ventilator decreases or completely disappears, in order to keep the pressure level at the mask end unchanged, the ventilator adjusts the compensation pressure according to the leakage situation and reduces the pressure support. At this time, the baseline flow rate will decrease. When calculating the tidal volume based on the original baseline flow rate, the inspiratory tidal volume is less than the expiratory tidal volume, and the average error between the calculated inspiratory tidal volume and the expiratory tidal volume

[0055] The calibration factor of the inspiratory baseline flow rate L 1 is The updated inspiratory baseline flow rate is L 1 -MQ 3 ;

[0056] The calibration factor of the expiratory baseline flow rate L 2 is The updated expiratory baseline flow rate is L 2 -MQ 4 ;

[0057] The inspiratory baseline flow rate and the expiratory baseline flow rate remain stable until the inspiratory tidal volume and the expiratory tidal volume return to being equal again.

[0058] In addition, the present invention also provides a tidal volume detection device, as Figure 4 shown. The tidal volume detection device of the ventilator includes: a ventilator data acquisition module 101 for acquiring the target pressure of the ventilator and the real-time instantaneous flow rate value of the ventilator; a baseline flow rate acquisition module 102 for acquiring the baseline flow rate under the target pressure; a time threshold acquisition module 103 for acquiring the time threshold of the inspiratory phase and the time threshold of the expiratory phase; a flow rate difference acquisition module 104 for acquiring the flow rate difference between the instantaneous flow rate and the inspiratory baseline flow rate during the inspiratory phase, and the difference between the instantaneous flow rate and the expiratory baseline flow rate during the expiratory phase; a tidal volume calculation module 105 for performing integral operation according to the flow rate difference and the time threshold to obtain the inspiratory tidal volume and the expiratory tidal volume.

[0059] Furthermore, the above-mentioned tidal volume detection device further includes a baseline flow rate calibration module 106, which calculates and obtains the new inspiratory and expiratory baseline flow rates according to the difference between the slope of the flow rate curve generated by the instantaneous flow rate, the time threshold and the tidal volume.

[0060] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A tidal volume detection device for a bilevel ventilator, characterized in that, it includes: a ventilator data acquisition module (101) for acquiring the target pressure of the bilevel ventilator and the real-time instantaneous flow rate value F of the bilevel ventilator; Baseline flow rate acquisition module (102) for acquiring baseline flow rates L during the inhalation and exhalation phases under the target pressure 1 and L 2 ; A time threshold acquisition module (103) for acquiring a time threshold t of an inhalation phase i and a time threshold t of an exhalation phase e ; The flow rate difference acquisition module (104) is configured to obtain the flow rate difference ΔF between the instantaneous flow rate F and the inspiratory phase base flow rate L during the inspiratory phase 1 ΔF 1 , and the difference ΔF between the instantaneous flow rate F and the expiratory phase base flow rate L during the expiratory phase 2 ΔF 2 ; Tidal volume calculation module (105), configured to perform an integration operation based on the flow rate difference and the time threshold to obtain the inspiratory tidal volume V i and the expiratory tidal volume V e ; The basic flow rate calibration module (106) is used to calculate based on the difference between the slope of the flow rate curve generated from the instantaneous flow rate, the time threshold, and the tidal volume, and obtain the new inspiratory and expiratory basic flow rates; extract the slope θ of the flow rate curve at the intersection of the flow rate curve generated from the instantaneous flow rate and the inspiratory basic flow rate curve 1 , θ 2 , and the slope θ of the flow rate curve at the intersection with the expiratory basic flow rate curve 3 , θ 4 ; Calculate the average error between the inspiratory tidal volume and the expiratory tidal volume When the inspiratory tidal volume V i is greater than the expiratory tidal volume V e : Inspiratory baseline flow rate L 1 has a calibration factor of The updated inspiratory baseline flow rate is L 1 +MQ 1 ; The expiratory baseline flow rate L 2 has a calibration factor of The updated expiratory baseline flow rate is L 2 + MQ 2 ; When the inspiratory tidal volume V i is less than the expiratory tidal volume V e : Inspiratory phase baseline flow rate L 1 has a calibration factor of The updated inspiratory phase baseline flow rate is L 1 -MQ 3 ; The expiratory baseline flow rate L 2 has a calibration factor of The updated expiratory baseline flow rate is L 2 -MQ 4 .

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