CN113440124A - Detection method and system for determining lung over-expansion by using electrical impedance tomography - Google Patents
Detection method and system for determining lung over-expansion by using electrical impedance tomography Download PDFInfo
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/053—Measuring electrical impedance or conductance of a portion of the body
- A61B5/0536—Impedance imaging, e.g. by tomography
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/0806—Detecting, measuring or recording devices for evaluating the respiratory organs by whole-body plethysmography
Abstract
The present disclosure describes a detection method for determining lung hyper-distension using electrical impedance tomography for detecting factors causing at least one lung hyper-distension based on electrical impedance tomography images. The detection method comprises the steps of judging whether an area with over-inflated lungs exists in the area of interest based on a first lung compliance corresponding to a first positive end expiratory pressure and a second lung compliance corresponding to a second positive end expiratory pressure; determining whether lung over-expansion is caused by an increase in end-expiratory positive pressure based on an actual end-expiratory gas volume reference change for the second positive end-expiratory pressure and the first positive end-expiratory pressure and an end-expiratory gas volume reference change predicted based on the first lung compliance; and determining whether the lung is over inflated by tidal volume based on the actual change in the gas volume reference values at the end-tidal of the second positive end-expiratory pressure and the end-expiratory of the first positive end-expiratory pressure and the change in the gas volume reference value predicted based on the first lung compliance. From this, the factor causing lung over-inflation can be determined.
Description
Technical Field
The present disclosure relates generally to a detection method and system for determining lung hyperinflation using electrical impedance tomography.
Background
In respiratory and critical medicine, mechanical ventilation therapy is suitably applied to save the lives of many critically ill patients. Ventilators have been commonly used in various clinical settings (e.g., pulmonary reoccurrence, positive end-expiratory pressure titration, or pulmonary reoccurrence assessment) to prevent or treat respiratory failure as an effective means to artificially replace the function of spontaneous ventilation.
Currently, in the clinic, a ventilator is often used to set a corresponding pulmonary protective ventilation strategy to perform the pulmonary protective ventilation on a patient. For example, to ensure ventilation, the ventilator may be used to reduce the tidal volume as much as possible, and then apply a positive end-expiratory pressure to the lung in an amount that will open the alveoli at the end of expiration. However, even if a small tidal volume (e.g., tidal volume may be 6 to 8ml/kg) or sufficient positive end-tidal pressure is set by the ventilator to provide protective lung ventilation to the patient, there is still a possibility of lung over-inflation as the positive end-tidal pressure rises, whether this lung over-inflation is caused by the positive end-tidal pressure itself or by the tidal volume at high positive end-tidal pressure, which has yet to be investigated.
Disclosure of Invention
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a detection method and a detection system for determining lung hyper-expansion using electrical impedance tomography, which can determine a factor causing lung hyper-expansion.
To this end, a first aspect of the present disclosure provides a detection method for determining lung hyper-distension using electrical impedance tomography, for detecting a factor causing at least one lung hyper-distension based on electrical impedance tomography images obtained by an electrical impedance detection apparatus, comprising: acquiring a first lung compliance corresponding to a first positive end-expiratory pressure and a second lung compliance corresponding to a second positive end-expiratory pressure of each pixel of a region of interest of at least one lung obtained based on the electrical impedance tomography image, judging whether an over-inflated region of the lung exists in the region of interest based on the first lung compliance and the second lung compliance, and if the over-inflated region of the lung exists, taking the over-inflated region of the lung as a first target region, wherein the first positive end-expiratory pressure is smaller than the second positive end-expiratory pressure; acquiring a difference value between an end-expiratory gas volume reference value of the second positive end-expiratory pressure and an end-expiratory gas volume reference value of the first positive end-expiratory pressure of each pixel of the first target area as a first end-expiratory gas volume reference value change, acquiring a difference value between the end-expiratory gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and the end-expiratory gas volume reference value of the first positive end-expiratory pressure of each pixel of the first target area as a second end-expiratory gas volume reference value change, and taking a difference value between the first end-expiratory gas volume reference value change and the second end-expiratory gas volume reference value change of each pixel in the first target area as a first difference value, if the first difference value of the pixels in the first target area is smaller than a preset difference value, judging that the pixel lung is over-inflated due to the rise of the end-expiratory pressure, if the first difference value of the pixels in the first target area is not smaller than the preset difference value, taking the area corresponding to the pixels as a second target area and judging whether the lung over-expansion of the second target area is caused by tidal volume, wherein the preset difference value is smaller than 0; and in determining whether the second target area lung over-expansion is caused by tidal volume, acquiring a difference value between an end-tidal gas volume reference value of the second positive end-expiratory pressure and an end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target area as a first gas volume reference value change, acquiring a difference value between the end-tidal gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and the end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target area as a second gas volume reference value change, and taking the difference value between the first gas volume reference value and the second gas volume reference value change for each pixel in the second target area as a second difference value, if the second difference value of the pixel in the second target area is less than 0, judging that the lung of the pixel is over-inflated due to the tidal volume, and if the second difference value of the pixels in the second target area is larger than 0, judging that the lung of the pixel is not over-inflated.
In the disclosure, a region with lung over-expansion is determined based on a first lung compliance and a second lung compliance, whether the region with lung over-expansion is caused by the rise of the positive end-expiratory pressure is judged by comparing the change of the actual end-expiratory gas volume reference value of the second positive end-expiratory pressure with the first positive end-expiratory pressure with the change of the end-expiratory gas volume reference value predicted based on the first lung compliance, and if the lung over-expansion is not determined to be caused by the rise of the positive end-expiratory pressure, whether the lung over-expansion is caused by the tidal volume is judged by comparing the change of the actual end-expiratory gas volume reference value of the second positive end-expiratory pressure with the change of the actual end-expiratory gas volume reference value of the first positive end-expiratory pressure with the change of the gas volume reference value predicted based on the first lung compliance. From this, the factor causing lung over-inflation can be determined.
In addition, in the detection method according to the first aspect of the present disclosure, optionally, a difference between the second lung compliance and the first lung compliance of each pixel in the region of interest is acquired as a lung compliance difference, and if there is a pixel whose lung compliance difference is smaller than 0, a region corresponding to the pixel is regarded as the region in which the lung is excessively inflated. This makes it possible to determine whether or not there is a region of lung over-inflation.
In addition, in the detection method according to the first aspect of the present disclosure, optionally, the number of the regions of interest is one or more, and a total area of the regions of interest is smaller than or equal to an area of a lung corresponding to the electrical impedance tomography image. Thereby, a local region of the lung can be selected to detect a factor causing lung over-inflation or a factor causing lung over-inflation can be detected for the entire region corresponding to the electrical impedance tomography image.
Further, in the detection method according to the first aspect of the present disclosure, optionally, a first lung compliance C of pixels in the region of interestEIT,1Satisfies the formula: cEIT,1＝TV1/ΔP1Wherein, TV1Representing a tidal volume reference value, Δ P, corresponding to the first positive end expiratory pressure1Representing a driving pressure corresponding to the first positive end-expiratory pressure; a second lung compliance C of pixels in the region of interestEIT,2Satisfies the formula: cEIT,2＝TV2/ΔP2Wherein, TV2Representing a tidal volume reference value, Δ P, corresponding to the second positive end expiratory pressure2And represents a driving pressure corresponding to the second positive end-expiratory pressure.
Further, in the detection method according to the first aspect of the present disclosure, optionally, the tidal volume reference value is at least one of a tidal volume and a tidal electrical impedance change, and the gas volume reference value is at least one of a lung volume, an electrical impedance, and a lung gas volume. In this case, a variety of tidal volume and gas volume references can be supported. This can improve compatibility.
In addition, in the detection method according to the first aspect of the present disclosure, optionally, the first difference value Δ V of the pixels in the first target regionPSatisfies the formula: Δ VP＝ΔEELI1–ΔEELI2Wherein, Δ EELI1Indicating a change in the first end-tidal gas volume reference, Δ EELI2Indicating a change in the second end-tidal gas volume reference, Δ EELI2＝(CEIT,1×ΔPEEP)，CEIT,1Indicative of the first lung compliance, and Δ PEEP indicative of the second positive end-expiratory pressure minus the first positive end-expiratory pressure. Thereby, the first difference value can be obtained.
In addition, in the detection method according to the first aspect of the present disclosure, optionally, the second difference value Δ V of the pixels in the second target regionPVSatisfies the formula: Δ VPV＝VPV,1-VPV,2Wherein V isPV,1Indicating a change in the first gas volume reference value, VPV,2Representing a change in said second gas volume reference value, VPV,1＝ΔEELI1+TV2，ΔEELI1Representing a change in said first end-tidal gas volume reference value, TV2Representing a tidal volume reference value, V, corresponding to said second positive end-expiratory pressurePV,2＝CEIT,1×(ΔPEEP+ΔP2)，CEIT,1Indicating the first lung compliance, Δ PEEP indicating the second positive end-expiratory pressure minus the first positive end-expiratory pressure, Δ P2And represents a driving pressure corresponding to the second positive end-expiratory pressure. Thereby, the second difference value can be obtained.
In addition, in the detection method according to the first aspect of the present disclosure, optionally, the preset difference is a preset multiple of the lung compliance difference. Thereby, the preset difference can be determined based on the lung compliance difference.
Further, in the detection method according to the first aspect of the present disclosure, optionally, the tidal volume reference value is a gas volume obtained by normalizing tidal electrical impedance change. In this case, normalizing the tidal electrical impedance change to gas volume can be a unified unit of computation. This makes it possible to easily perform subsequent determination.
A second aspect of the present disclosure provides a detection system for determining lung over-inflation using electrical impedance tomography, using the detection method described above to detect a factor causing lung over-inflation.
According to the present disclosure, a detection method and system for determining lung over-expansion using electrical impedance tomography can be provided, which determines factors causing lung over-expansion.
Drawings
The disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings, in which:
fig. 1 is a diagram illustrating an application scenario of a detection method for determining lung hyper-distension using electrical impedance tomography according to an example of the present disclosure.
Fig. 2 is a flow chart illustrating a detection method for determining lung hyperinflation using electrical impedance tomography in accordance with an example of the present disclosure.
Fig. 3 is a flow chart illustrating determining whether there is a region of lung hyper-expansion in accordance with an example of the present disclosure.
Fig. 4 is a schematic diagram illustrating an electrical impedance tomography image of a lung according to an example of the present disclosure.
Fig. 5 is a schematic diagram illustrating a detection method, taking a lung volume as an example, according to an example of the present disclosure.
Fig. 6 is a flow chart illustrating a determination of whether lung over-inflation is caused by an increase in positive end expiratory pressure according to examples of the present disclosure.
Fig. 7 is a flow chart illustrating determining whether lung over-inflation is caused by tidal volume according to examples of the present disclosure.
Detailed Description
Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals, and redundant description thereof is omitted. The drawings are schematic and the ratio of the dimensions of the components and the shapes of the components may be different from the actual ones. It is noted that the terms "comprises," "comprising," and "having," and any variations thereof, in this disclosure, for example, a process, method, system, article, or apparatus that comprises or has a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include or have other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. All methods described in this disclosure can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
The detection method and system for determining lung over-inflation by utilizing electrical impedance tomography can determine the factors causing the lung over-inflation (namely, can determine whether the lung over-inflation is caused by the rising of the positive end-expiratory pressure or the rising tidal volume of the positive end-expiratory pressure). The detection method for determining lung hyper-distension using electrical impedance tomography according to the present disclosure may also be referred to simply as a detection method, a measurement method, an identification method, or a lung hyper-distension detection method.
The electrical impedance tomography related to the present disclosure may be to apply a current with a certain frequency and amplitude to an object to be imaged through an electrode set arranged on the surface of the object to be imaged, measure a response voltage, and finally obtain an image capable of reflecting electrical impedance distribution information inside the object to be imaged by using a corresponding imaging algorithm. In some examples, electrode sets may be arranged on the chest of the object to be imaged to obtain images reflecting pulmonary electrical impedance distribution information of the object to be imaged (i.e., electrical impedance tomography images). In some examples, electrical impedance tomography may be used to titrate the optimal positive end expiratory pressure at the bedside. Thereby, the risk of over-expansion or collapse of different lung areas can be reduced.
In addition, each pixel of the electrical impedance tomography image related to the present disclosure can represent the distribution of electrical impedance detected at different time points in each respiratory cycle at the same position in the lung. Such as end-of-breath electrical impedance or end-of-inspiration electrical impedance. In this case, the electrical impedance changes of the individual pixels at different time nodes can be acquired and the tidal volume, lung volume or lung gas volume and corresponding changes, e.g. lung volume changes, of the individual pixels can be acquired on the basis of the electrical impedance. In some examples, the tidal electrical impedance change corresponding to each pixel of the electrical impedance tomography image may be used as a reference value for the tidal volume of each pixel.
Additionally, the positive end-expiratory pressure (PEEP) to which the present disclosure relates may be the positive pressure that remains in the respiratory tract at the end of the respiratory cycle. Sometimes also referred to as positive end expiratory pressure. In some examples, the positive end expiratory pressure may be set by a ventilator.
Additionally, Tidal Volume (VT) to which the present disclosure relates may be the Volume of gas that is inhaled or exhaled each time during a quiet breath. In some examples, the tidal volume may be set by a ventilator.
The detection method according to the present disclosure is described in detail below with reference to the drawings. In addition, the application scenarios described in the examples of the present disclosure are for more clearly illustrating the technical solutions of the present disclosure, and do not constitute a limitation on the technical solutions provided by the present disclosure. Fig. 1 is a diagram illustrating an application scenario of a detection method for determining lung hyper-distension using electrical impedance tomography according to an example of the present disclosure.
As shown in fig. 1, in a clinical scenario (for example, pulmonary atelectasis, PEEP titration, pulmonary atelectasis, etc.) in which a ventilator 10 is used to increase positive end-expiratory pressure (PEEP), an image reflecting electrical impedance distribution information of a lung may be acquired by electrical impedance tomography (an image acquired by electrical impedance tomography may be referred to as an electrical impedance tomography image, and may also be referred to as an electrical impedance image in some cases), and then a factor causing lung over-expansion may be determined based on the electrical impedance image and by using the detection method according to the present disclosure. In some examples, the set of electrodes 21 may be arranged on the patient's chest by the electrical impedance detection device 20 to obtain electrical impedance images of the lungs. That is, electrical impedance images may be obtained by the electrical impedance detection apparatus 20.
In some examples, the detection method may identify factors causing lung over-inflation at bedside. Thereby, the factor causing the lung to be over-inflated can be easily and quickly identified at the bedside. In some examples, the detection may be performed after completion of at least one exhalation cycle.
In some examples, the detection method may be integrated in the ventilator 10 or the electrical impedance detection apparatus 20 in the form of computer program instructions. Thereby, the factor causing the lung to be over-inflated can be easily determined. In some examples, the detection method may be stored on and executed by a server in the form of computer program instructions. In some examples, a server may include one or more processors and one or more memories. Wherein the processor may include a central processing unit, a graphics processing unit, and any other electronic components capable of processing data, capable of executing computer program instructions. The memory may be used to store computer program instructions. In some examples, the server may implement the detection method by executing computer program instructions on the memory. In some examples, the server may also be a cloud server.
Hereinafter, the detection method according to the present disclosure will be described in detail with reference to the drawings. In some examples, the detection method may be a method for detecting a factor causing at least one lung to be over-inflated based on the electrical impedance tomography image. Fig. 2 is a flow chart illustrating a detection method for determining lung hyperinflation using electrical impedance tomography in accordance with an example of the present disclosure. Fig. 3 is a flow chart illustrating determining whether there is a region of lung hyper-expansion in accordance with an example of the present disclosure.
As shown in fig. 2, in some examples, the detection method may include determining whether there is a region of lung hyper-expansion (step S110).
In some examples, in step S110, it may be determined whether there is an area of lung over-inflation by comparing a first lung compliance corresponding to the first positive end-expiratory pressure and a second lung compliance corresponding to the second positive end-expiratory pressure.
In some examples, the first positive end-expiratory pressure may be less than the second positive end-expiratory pressure. That is, the first positive end-expiratory pressure may be a low positive end-expiratory pressure and the second positive end-expiratory pressure may be a high positive end-expiratory pressure. In this case, a change in lung compliance at an elevated positive end expiratory pressure can be obtained.
In some examples, as shown in fig. 3, step S110 may include acquiring a first lung compliance corresponding to the first positive end-expiratory pressure and a second lung compliance corresponding to the second positive end-expiratory pressure (step S111), acquiring a lung compliance difference (step S112), determining whether there are pixels with a lung compliance difference less than 0 (step S113), and acquiring a region of lung over-inflation (step S114).
As described above, in some examples, step S110 may include acquiring a first lung compliance for the first positive end-expiratory pressure and a second lung compliance for the second positive end-expiratory pressure (step S111).
In some examples, the first lung compliance corresponding to the first positive end-expiratory pressure and the second lung compliance corresponding to the second positive end-expiratory pressure may be a lung compliance of each pixel of a region of interest of the at least one lung obtained based on the electrical impedance tomography image. That is, a first lung compliance corresponding to a first positive end-expiratory pressure and a second lung compliance corresponding to a second positive end-expiratory pressure for each pixel of the region of interest of the at least one lung may be obtained based on the electrical impedance tomography images. In some examples, the first and second lung compliance may be lung compliance for one or more respiratory cycles.
In some examples, the number of regions of interest may be one or more. In some examples, the total area of the region of interest may be less than the area of the lung corresponding to the electrical impedance tomography image. This enables detection of a factor causing lung hyper-expansion in a local region of the lung. In some examples, the total area of the region of interest may be equal to the area of the lung corresponding to the electrical impedance tomography image. That is, the region of interest may be a region of the lung corresponding to the electrical impedance tomography image (the region of the lung may be simply referred to as a lung region). Thereby, it is possible to detect a factor causing lung over-expansion in all regions corresponding to the electrical impedance tomography image.
In some examples, the region of interest may be a region of the lung region corresponding to the electrical impedance tomography image in which the change in tidal impedance is greater than 20% of the maximum change in tidal impedance.
Fig. 4 is a schematic diagram illustrating an electrical impedance tomography image of a lung according to an example of the present disclosure. Unless specifically stated, the present disclosure relates to the electrical impedance or impedance of a pixel, both referring to the electrical impedance of a pixel in an electrical impedance tomography image. As an example, fig. 4 shows a schematic diagram of an electrical impedance tomography image of a lung.
Generally, lung compliance may refer to the change in lung volume caused by a change in unit pressure. The lung compliance may include static lung compliance or dynamic lung compliance. In some examples, at a given positive end-expiratory pressure based on the electrical impedance tomography image, a tidal volume reference value for each pixel in the electrical impedance tomography image may be acquired and a lung compliance for each pixel calculated from the tidal volume reference value and a driving pressure corresponding to the given positive end-expiratory pressure. Examples of the disclosure are not so limited and in other examples, lung compliance may be calculated using other means.
In some examples, a first lung compliance C of pixels in the region of interestEIT,1The formula can be satisfied:
CEIT,1＝TV1/ΔP1，
wherein, TV1May represent a corresponding tidal volume reference, Δ P, at a first end-expiratory positive pressure1A driving pressure corresponding to the first positive end-expiratory pressure may be indicated.
In some examples, the second lung compliance C of the pixels in the region of interestEIT,2The formula can be satisfied:
CEIT,2＝TV2/ΔP2，
wherein, TV2May represent a corresponding tidal volume reference, Δ P, at a second end-expiratory positive pressure2A driving pressure corresponding to the secondary positive end-expiratory pressure may be indicated.
In some examples, the tidal volume reference value may be at least one of a tidal volume and a tidal electrical impedance change. In this case, a variety of tidal volume references can be supported. This can improve compatibility. For example, if tidal volume is available, lung compliance may be calculated based on the tidal volume, and if electrical impedance is available, lung compliance may be calculated based on tidal electrical impedance changes.
In some examples, the tidal electrical impedance change may be the end-inspiratory electrical impedance minus the end-expiratory electrical impedance. In some examples, tidal volume may be obtained by lung volume changes and lung gas volume changes. Here, the lung volume change may be the end-inspiratory lung volume minus the end-expiratory lung volume, and the lung gas volume change may be the end-inspiratory lung gas volume minus the end-expiratory lung gas volume.
In some examples, tidal volume reference values for pixels in the region of interest may be obtained based on electrical impedance tomography images. In some examples, if the tidal volume reference value is a tidal volume, the tidal volume of each pixel may be obtained based on a percentage of tidal electrical impedance changes of each pixel over total tidal electrical impedance changes of the electrical impedance tomography image. For example, assuming that the total tidal electrical impedance of the electrical impedance tomography image changes to 1000 Ω, the ventilator set tidal volume is 500ml at a time, and if the tidal electrical impedance of a pixel in the region of interest changes to 50 Ω (i.e., 5% by weight), the tidal volume reference for that pixel may be 25 ml. In some examples, if the tidal volume reference value is a tidal electrical impedance change, it can be used directly as a reference value for the tidal volume to calculate lung compliance.
In some examples, the tidal volume reference value may be a volume of gas obtained by normalizing the tidal electrical impedance changes (i.e., the tidal electrical impedance changes may be normalized to the volume of gas and used as a reference value for the tidal volume for calculating lung compliance). In this case, normalizing the tidal electrical impedance change to gas volume can be a unified unit of computation. This makes it possible to easily perform subsequent determination. In some examples, during the normalization process, a tidal volume corresponding to a unit tidal electrical impedance change may be obtained. Consequently, the tidal electrical impedance change can be subsequently converted to a gas volume based on the tidal volume corresponding to the unit tidal electrical impedance change. To better illustrate the normalization process, assuming that the tidal volume set by the ventilator is 500ml at a time, and the corresponding tidal electrical impedance change is 1000 Ω, a tidal electrical impedance change of 1 Ω may correspond to a tidal volume of 0.5ml, and if the tidal electrical impedance change of 50 Ω for a pixel, the gas volume for that pixel may be 0.5ml × 50 — 25 ml.
In some examples, the driving pressure may be equal to the plateau pressure minus the positive end-expiratory pressure. The plateau pressure may be the airway pressure at the end of inspiration pause. In this embodiment, the driving pressure corresponding to the first positive end-expiratory pressure may be a plateau pressure corresponding to the first positive end-expiratory pressure minus the first positive end-expiratory pressure, and the driving pressure corresponding to the second positive end-expiratory pressure may be a plateau pressure corresponding to the second positive end-expiratory pressure minus the second positive end-expiratory pressure.
Fig. 5 is a schematic diagram illustrating a detection method, taking a lung volume as an example, according to an example of the present disclosure.
To more clearly illustrate the detection method according to the present disclosure, fig. 5 shows a schematic diagram of the detection method, taking the lung volume as an example. As shown in fig. 5, the abscissa may be pressure and the ordinate may be lung volume. First lung compliance CEIT,1And second lung compliance CEIT,2Which may correspond to the lung compliance of one respiratory cycle, respectively.
In addition, first lung compliance CEIT,1The corresponding abscissa may be the first positive end expiratory pressure PEEP1Corresponding driving pressure Δ P1First lung compliance CEIT,1The corresponding ordinate may be the first positive end expiratory pressure PEEP1Corresponding tidal volume reference value TV1(where the tidal volume reference is the tidal volume and is obtained based on lung volume changes), where Δ P1＝PAW1-PEEP1，PAW1May represent a first positive end expiratory pressure, PEEP1And (5) corresponding platform pressure.
In addition, second lung compliance CEIT,2The corresponding abscissa may be the second positive end expiratory pressure PEEP2Corresponding driving pressure Δ P2Second lung compliance CEIT,2The corresponding ordinate may be the second positive end expiratory pressure PEEP2Corresponding tidal volume reference value TV2Wherein, Δ P2＝PAW2-PEEP2，PAW2May represent a secondary positive end expiratory pressure, PEEP2And (5) corresponding platform pressure.
As described above, in some examples, a first lung compliance corresponding to a first positive end-expiratory pressure and a second lung compliance corresponding to a second positive end-expiratory pressure for each pixel of a region of interest of at least one lung may be obtained based on electrical impedance tomography images. In some examples, whether there is an area of lung hyper-expansion in the region of interest may be determined based on the first lung compliance and the second lung compliance. One way of determining whether there is an area of lung over-inflation in the region of interest based on the first lung compliance and the second lung compliance is described below in connection with steps S112 to S114 and does not constitute a limitation on the technical solution provided by the present disclosure.
As described above, in some examples, step S110 may include obtaining a lung compliance difference value (step S112). In step S112, a difference of the second lung compliance and the first lung compliance for each pixel in the region of interest may be acquired as a lung compliance difference. In some examples, the lung compliance difference Δ C for pixels in the region of interestEITThe formula can be satisfied: delta CEIT＝CEIT,2-CEIT,1。
As described above, in some examples, step S110 may include determining whether there is a pixel having a lung compliance difference value less than 0 (step S113). In some examples, in step S113, if there is a pixel with a lung compliance difference smaller than 0, the process may proceed to step S114. In some examples, the region corresponding to pixels for which the lung compliance difference is greater than 0 may be a region of lung renaturation. In some examples, the lung compliance difference value is equal to 0 may be negligible (i.e., pixels with lung compliance difference value equal to 0 may not be determined).
As described above, in some examples, step S110 may include acquiring a region of lung hyper-expansion (step S114). In some examples, in step S114, a region corresponding to a pixel having a lung compliance difference less than 0 may be taken as a region of lung over-inflation. That is, there are areas of lung over-inflation in the region of interest. This makes it possible to determine whether or not there is a region of lung over-inflation. In some examples, a region of lung over-inflation may be taken as the first target region.
As described above, it may be determined whether there is a lung over-inflated region at step S110. In this case, it is necessary to further judge the factor (which may also be referred to as a cause) causing the lung to be excessively swollen. In some examples, the factor causing lung hyperinflation may be further determined based on the volume of lung re-expansion caused by an increase in end-expiratory pressure or the volume of lung hyperinflation caused by an increase in end-expiratory pressure.
As shown in fig. 2, in some examples, the detection method may include determining whether a lung is over-inflated by an increase in positive end expiratory pressure (step S120).
In some examples, in step S120, the difference between the actual end-tidal gas volume reference values for the first and second positive end-tidal pressures and the end-tidal gas volume reference value predicted based on the first compliance may be compared to determine whether an increase in the positive end-tidal pressure causes excessive lung expansion.
In some examples, the gas volume reference value may be at least one of a lung volume, an electrical impedance, and a lung gas volume. In some examples, different gas volume reference values may be obtained by respective auxiliary devices, and detection may be enabled based on the respective gas volume reference values. In this case, a plurality of gas capacity reference values can be supported. This can improve compatibility.
In some examples, the gas volume reference value may correspond to a tidal volume reference value. For example, if the tidal volume reference is a tidal volume, the gas volume reference may be a lung volume or a lung gas volume. For another example, if the tidal volume reference is a tidal electrical impedance change, the gas volume reference may be an electrical impedance. In other examples, the gas volume reference value may not correspond to the tidal volume reference value. In this case, the gas volume reference and tidal volume reference may be normalized to a uniform unit of computation. For example, the uniform calculation unit may be, for example, ml (milliliters) or Ω (ohms).
Fig. 6 is a flow chart illustrating a determination of whether lung over-inflation is caused by an increase in positive end expiratory pressure according to examples of the present disclosure.
In some examples, as shown in fig. 6, step S120 may include obtaining a difference between an actual end-tidal gas volume reference value and a predicted end-tidal gas volume reference value (step S121), obtaining a first difference (step S122), determining whether the first difference meets a preset condition (step S123), and obtaining a second target region (step S124).
As described above, in some examples, step S120 may include obtaining a difference in the actual end-tidal gas volume reference value and a difference in the predicted end-tidal gas volume reference value (step S121).
In some examples, the difference in the actual end-tidal gas volume reference value may be a difference in the end-tidal gas volume reference value of the second positive end-expiratory pressure and the end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel of the first target region. In some examples, the difference in the actual end-tidal gas volume reference values may be taken as the first end-tidal gas volume reference value change.
In some examples, the difference in the predicted end-tidal gas volume reference value may be a difference in the end-tidal gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and the end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel of the first target region. In some examples, the difference in the predicted end-tidal gas volume reference values may be changed as a second end-tidal gas volume reference value. In some examples, an extrapolation operation may be performed on the first lung compliance to obtain a second end-tidal gas volume reference change.
As described above, in some examples, step S120 may include obtaining a first difference value (step S122). In some examples, a difference in the first end-tidal gas volume reference value and the second end-tidal gas volume reference value for each pixel in the first target region may be taken as the first difference.
In some examples, the first difference Δ V of pixels in the first target regionPThe formula can be satisfied:
ΔVP＝ΔEELI1–ΔEELI2，
wherein, Delta EELI1Can represent the change in the first end-tidal gas volume reference, Δ EELI2A change in the second end-tidal gas volume reference value may be indicated. Thereby, the first difference value can be obtained.
In some examples, the second end-tidal gas volume reference value changes by Δ EELI2The formula can be satisfied:
ΔEELI2＝(CEIT,1×ΔPEEP)， (1)
wherein, CEIT,1The first lung compliance may be indicated and Δ PEEP may indicate the second positive end-expiratory pressure minus the first positive end-expiratory pressure. In this case, the difference in the end-tidal gas volume reference value can be predicted based on the first lung compliance.
As an example, as shown in FIG. 5, where the gas volume reference is lung volume, the first end-tidal gas volume reference varies by Δ EELI1The end-expiratory lung volume of the first positive end-expiratory pressure may be subtracted from the end-expiratory lung volume of the second positive end-expiratory pressure. Second end-tidal gas volume reference change Δ EELI2The end-expiratory lung volume of the first positive end-expiratory pressure may be subtracted from the end-expiratory lung volume of the second positive end-expiratory pressure predicted based on the first lung compliance. That is, the second end-tidal gas volume reference value change Δ EELI2The above formula (1) can be satisfied. In this case, Δ EELI varies based on the first end-tidal gas volume reference value1And second end-tidal gasVolume capacity reference change Δ EELI2The first difference value DeltaV can be obtainedP。
As described above, in some examples, step S120 may include determining whether the first difference value meets a preset condition (step S123).
In some examples, if the first difference value of a pixel in the first target region meets a preset condition, it may be determined that the lung of the pixel is over-inflated due to the increase of the positive end expiratory pressure. In some examples, the preset condition may be that the first difference is smaller than a preset difference, wherein the preset difference may be smaller than 0 (i.e., the preset condition may be that the first difference is smaller than 0 and the absolute value of the first difference is larger than the absolute value of the preset difference). In this case, the first difference is large enough to determine that the lung is over-inflated by an increase in positive end expiratory pressure.
In some examples, the first difference may be the volume of lung re-expansion caused by an increase in positive end expiratory pressure when the first difference is greater than 0. In some examples, the first difference may be the volume of lung over-expansion caused by an increase in positive end expiratory pressure when the first difference is less than 0. In some examples, if the absolute value of the volume of lung over-expansion caused by the increase in end-expiratory positive pressure is greater than the absolute value of the preset difference, it may be determined that lung over-expansion is caused by the increase in end-expiratory positive pressure (i.e., the volume of lung over-expansion caused by the increase in end-expiratory positive pressure is sufficiently large to determine that lung over-expansion is caused by the increase in end-expiratory positive pressure), otherwise further determination is required (see step S130).
In some examples, if the first difference value of the pixels in the first target region does not meet the preset condition (i.e., the first difference value is not less than the preset difference value), the process may proceed to step S124. In some examples, the preset difference may be a preset multiple of the lung compliance difference. For example, the preset multiple may be 1, 2, or 3, etc. In this case, the preset difference can be determined based on the lung compliance difference, and it can be accurately determined whether the first difference is large enough to determine that the lungs are over inflated due to the increase in positive end expiratory pressure.
As described above, in some examples, step S120 may include acquiring a second target region (step S124). In some examples, an area corresponding to a pixel of the first target area whose first difference value does not meet a preset condition may be used as the second target area. In some examples, a determination may continue as to whether the second target region lung is over-inflated by tidal volume (described later). In some examples, the case where the first difference value of the pixels in the first target region is equal to 0 may be negligible (i.e., the pixels whose first difference value is equal to 0 may not be determined).
As shown in fig. 2, in some examples, the detection method may include determining whether a tidal volume causes a lung over inflation (step S130).
Fig. 7 is a flow chart illustrating determining whether lung over-inflation is caused by tidal volume according to examples of the present disclosure.
In some examples, as shown in fig. 7, step S130 (i.e., determining whether the second target region lung over-inflation process is caused by the tidal volume) may include obtaining a change in the actual tidal volume-induced gas volume reference value and a change in the predicted tidal volume-induced gas volume reference value (step S131), obtaining a second difference (step S132), determining whether the second difference is less than 0 (step S133), and determining that the lung over-inflation is caused by the tidal volume (step S134).
As described above, in some examples, step S130 may include obtaining an actual tidal volume induced gas volume reference change and a predicted tidal volume induced gas volume reference change (step S131).
In some examples, the actual tidal volume induced change in the gas volume reference value may be a difference of the end-tidal gas volume reference value of the second positive end-expiratory pressure and the end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target region. In some examples, a change in the gas volume reference due to an actual tidal volume may be taken as the first gas volume reference change.
In some examples, the predicted tidal volume induced gas volume reference value change may be a difference of an end-tidal gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and an end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target region. In some examples, a predicted tidal volume induced change in the gas volume reference value may be used as the second gas volume reference value change.
As described above, in some examples, step S130 may include obtaining a second difference value (step S132).
In some examples, a difference of the first gas volume reference value and the second gas volume reference value for each pixel in the second target area may be taken as the second difference.
In some examples, the second difference Δ V of the pixels in the second target regionPVThe formula can be satisfied:
ΔVPV＝VPV,1-VPV,2，
wherein, VPV,1Can indicate the change of the reference value of the first gas volume, VPV,1A change in the second gas capacity reference value may be indicated. Thereby, the second difference value can be obtained.
In some examples, the first gas capacity reference value varies by VPV,1The formula can be satisfied:
VPV,1＝ΔEELI1+TV2，
wherein, Delta EELI1Can indicate the change of the first end-tidal gas volume reference value, TV2May represent a tidal volume reference corresponding to the secondary positive end expiratory pressure.
In some examples, the second gas capacity reference value varies by VPV,2The formula can be satisfied:
VPV,2＝CEIT,1×(ΔPEEP+ΔP2)， (2)
wherein, CEIT,1May represent first lung compliance, Δ PEEP may represent second positive end-expiratory pressure minus first positive end-expiratory pressure, Δ P2A driving pressure corresponding to the secondary positive end-expiratory pressure may be indicated. In this case, the tidal volume induced gas volume reference value can be predicted based on the first lung compliance.
As an example, as shown in FIG. 5, the gas containerThe quantity reference value is the lung volume, and the first gas volume reference value is changed by VPV,1The end-expiratory lung volume of the first positive end-expiratory pressure may be subtracted from the end-inspiratory lung volume of the second positive end-expiratory pressure. Second gas volume reference value variation VPV,2The end-expiratory lung volume for the first positive end-expiratory pressure may be subtracted from the end-inspiratory lung volume for the second positive end-expiratory pressure predicted based on the first lung compliance. That is, the second end-tidal gas volume reference value varies by VPV,2The above formula (2) can be satisfied. In this case, the value V is varied based on the first gas capacity reference valuePV,1And a second gas volume reference value variation VPV,2The second difference value DeltaV can be obtainedPV。
As described above, in some examples, step S130 may include determining whether the second difference is less than 0 (step S133). In some examples, if the second difference value of the pixels in the second target region is less than 0, the process may proceed to step S134. In some examples, if the second difference value of the pixel in the second target region is greater than 0, it may be determined that the pixel does not have lung over inflation (i.e., the pixel may be determined to be lung refolding due to tidal volume). In some examples, the second difference value of the pixels in the second target region is negligible (i.e., the pixels having the second difference value equal to 0 may not be determined).
In some examples, if the second difference is greater than 0, the second difference may be taken as a capacity for tidal volume induced lung remodeling. In some examples, if the second difference is less than 0, the second difference may be taken as a capacity for lung over-inflation caused by tidal volume.
As described above, in some examples, step S130 may include determining that the lung is over-inflated by tidal volume (step S134). In some examples, in step S134, for a pixel with a second difference value less than 0, it may be determined that the pixel is caused by tidal volume to over-inflate the lung. In some examples, a region corresponding to a pixel in the second target region whose second difference value of the pixels is smaller than 0 may be taken as the third target region.
In some examples, the first target region, the second target region, and the third target region may be marked (e.g., may be marked with color). Thereby, the factors causing the lung to be over inflated in the lung area can be intuitively obtained.
In addition, the detection method of the present disclosure may be applied to detection based on a plurality of pixels. For example, the plurality of pixels may be two pixels, three pixels, four pixels, or ten pixels, etc. Specifically, the total corresponding values may be calculated for a plurality of pixels adjacent to each other in the electrical impedance imaging image as a whole, and the processing of the above steps S110 to S130 may be performed. In some examples, respective values of the plurality of pixels (e.g., the respective values may be a first lung compliance, a second lung compliance, a first difference, or a second difference) may be summed to obtain an overall respective value.
In some examples, the present disclosure also provides a detection system for determining lung over-inflation using electrical impedance tomography, which detects a factor causing lung over-inflation using the detection method described above.
The detection method and the detection system disclosed by the invention firstly determine the area with over-expansion of the lung based on the first lung compliance and the second lung compliance, then judge whether the over-expansion area of the lung is caused by the rise of the positive end-expiratory pressure by comparing the actual end-expiratory gas volume reference value change of the second positive end-expiratory pressure and the first positive end-expiratory pressure with the end-expiratory gas volume reference value change predicted based on the first lung compliance, and if the over-expansion area of the lung is not determined to be caused by the rise of the positive end-expiratory pressure, continuously judge whether the over-expansion of the lung is caused by the tidal volume by comparing the actual end-expiratory gas volume reference value change of the second positive end-expiratory pressure and the first positive end-expiratory pressure with the gas volume reference value change predicted based on the first lung compliance. From this, the factor causing lung over-inflation can be determined.
While the invention has been described in detail in connection with the drawings and the embodiments, it is to be understood that the above description is not intended to limit the invention in any way. Those skilled in the art can make modifications and variations to the present invention as needed without departing from the true spirit and scope of the invention, and such modifications and variations are within the scope of the invention.
Claims (10)
1. A detection method for determining lung hyper-distension using electrical impedance tomography for detecting at least one factor causing lung hyper-distension based on electrical impedance tomography images obtained by an electrical impedance detection apparatus, comprising: acquiring a first lung compliance corresponding to a first positive end-expiratory pressure and a second lung compliance corresponding to a second positive end-expiratory pressure of each pixel of a region of interest of at least one lung obtained based on the electrical impedance tomography image, judging whether an over-inflated region of the lung exists in the region of interest based on the first lung compliance and the second lung compliance, and if the over-inflated region of the lung exists, taking the over-inflated region of the lung as a first target region, wherein the first positive end-expiratory pressure is smaller than the second positive end-expiratory pressure; acquiring a difference value between an end-expiratory gas volume reference value of the second positive end-expiratory pressure and an end-expiratory gas volume reference value of the first positive end-expiratory pressure of each pixel of the first target area as a first end-expiratory gas volume reference value change, acquiring a difference value between the end-expiratory gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and the end-expiratory gas volume reference value of the first positive end-expiratory pressure of each pixel of the first target area as a second end-expiratory gas volume reference value change, and taking a difference value between the first end-expiratory gas volume reference value change and the second end-expiratory gas volume reference value change of each pixel in the first target area as a first difference value, if the first difference value of the pixels in the first target area is smaller than a preset difference value, judging that the pixel lung is over-inflated due to the rise of the end-expiratory pressure, if the first difference value of the pixels in the first target area is not smaller than the preset difference value, taking the area corresponding to the pixels as a second target area and judging whether the lung over-expansion of the second target area is caused by tidal volume, wherein the preset difference value is smaller than 0; and in determining whether the second target area lung over-expansion is caused by tidal volume, acquiring a difference value between an end-tidal gas volume reference value of the second positive end-expiratory pressure and an end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target area as a first gas volume reference value change, acquiring a difference value between the end-tidal gas volume reference value of the second positive end-expiratory pressure predicted based on the first lung compliance and the end-expiratory gas volume reference value of the first positive end-expiratory pressure for each pixel in the second target area as a second gas volume reference value change, and taking the difference value between the first gas volume reference value and the second gas volume reference value change for each pixel in the second target area as a second difference value, if the second difference value of the pixel in the second target area is less than 0, judging that the lung of the pixel is over-inflated due to the tidal volume, and if the second difference value of the pixels in the second target area is larger than 0, judging that the lung of the pixel is not over-inflated.
2. The detection method according to claim 1, characterized in that:
and acquiring a difference value between the second lung compliance and the first lung compliance of each pixel in the region of interest as a lung compliance difference value, and if a pixel with the lung compliance difference value smaller than 0 exists, taking the region corresponding to the pixel as the over-inflated region of the lung.
3. The detection method according to claim 1, characterized in that:
the number of the interested areas is one or more, and the total area of the interested areas is smaller than or equal to the area of the lung corresponding to the electrical impedance tomography image.
4. The detection method according to claim 1, characterized in that:
a first lung compliance C of pixels in the region of interestEIT,1Satisfies the formula: cEIT,1＝TV1/ΔP1Wherein, TV1Representing a tidal volume reference value, Δ P, corresponding to the first positive end expiratory pressure1Indicating the first positive end-expiratory pressure correspondenceThe driving pressure of (1);
a second lung compliance C of pixels in the region of interestEIT,2Satisfies the formula: cEIT,2＝TV2/ΔP2Wherein, TV2Representing a tidal volume reference value, Δ P, corresponding to the second positive end expiratory pressure2And represents a driving pressure corresponding to the second positive end-expiratory pressure.
5. The detection method according to claim 4, characterized in that:
the tidal volume reference value is at least one of a tidal volume and a tidal electrical impedance change, and the gas volume reference value is at least one of a lung volume, an electrical impedance, and a lung gas volume.
6. The detection method according to claim 1, characterized in that:
a first difference value Δ V of pixels in the first target regionPSatisfies the formula:
ΔVP＝ΔEELI1–ΔEELI2，
wherein, Delta EELI1Indicating a change in the first end-tidal gas volume reference, Δ EELI2Indicating a change in the second end-tidal gas volume reference, Δ EELI2＝(CEIT,1×ΔPEEP)，CEIT,1Indicative of the first lung compliance, and Δ PEEP indicative of the second positive end-expiratory pressure minus the first positive end-expiratory pressure.
7. The detection method according to claim 1, characterized in that:
a second difference value Δ V of pixels in the second target regionPVSatisfies the formula:
ΔVPV＝VPV,1-VPV,2，
wherein, VPV,1Indicating a change in the first gas volume reference value, VPV,2Representing a change in said second gas volume reference value, VPV,1＝ΔEELI1+TV2，ΔEELI1Representing the first end-tidal gasVariation of volume capacity reference value, TV2Representing a tidal volume reference value, V, corresponding to said second positive end-expiratory pressurePV,2＝CEIT,1×(ΔPEEP+ΔP2)，CEIT,1Indicating the first lung compliance, Δ PEEP indicating the second positive end-expiratory pressure minus the first positive end-expiratory pressure, Δ P2And represents a driving pressure corresponding to the second positive end-expiratory pressure.
8. The detection method according to claim 2, characterized in that:
the preset difference is a preset multiple of the lung compliance difference.
9. The detection method according to claim 4, characterized in that:
the tidal volume reference value is a gas volume obtained by normalizing tidal electrical impedance changes.
10. A detection system for determining lung over-expansion using electrical impedance tomography, characterized in that a factor causing lung over-expansion is detected using the detection method of any one of claims 1 to 9.
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