WO2022068677A1 - 一种基于胸阻抗的运动肺功能测量系统 - Google Patents

一种基于胸阻抗的运动肺功能测量系统 Download PDF

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WO2022068677A1
WO2022068677A1 PCT/CN2021/120106 CN2021120106W WO2022068677A1 WO 2022068677 A1 WO2022068677 A1 WO 2022068677A1 CN 2021120106 W CN2021120106 W CN 2021120106W WO 2022068677 A1 WO2022068677 A1 WO 2022068677A1
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thoracic impedance
signal
exercise
pulmonary function
measurement system
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马艺馨
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上海交通大学
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/0205—Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
    • A61B5/0004—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network characterised by the type of physiological signal transmitted
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02438—Detecting, measuring or recording pulse rate or heart rate with portable devices, e.g. worn by the patient
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/0809—Detecting, measuring or recording devices for evaluating the respiratory organs by impedance pneumography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/085—Measuring impedance of respiratory organs or lung elasticity
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/091—Measuring volume of inspired or expired gases, e.g. to determine lung capacity
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6802—Sensor mounted on worn items
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A61B5/725—Details of waveform analysis using specific filters therefor, e.g. Kalman or adaptive filters

Definitions

  • the invention relates to the field of medical detection, in particular to a thoracic impedance-based exercise lung function measurement system.
  • Cardiopulmonary exercise test is one of the pulmonary function tests commonly used in the world to measure the level of human respiratory and circulatory function. It can be used for the evaluation of functional exercise capacity, disease diagnosis, and judgment and treatment. Different from the static pulmonary function test, which only reflects the ventilation or ventilation status in the resting state, CPET firstly measures the whole set of pulmonary function of the human body in the resting state, and then continuously and dynamically monitors and records the in and out airflow, oxygen and carbon dioxide under different loads.
  • Detecting the dynamic changes of parameters such as oxygen consumption and carbon dioxide excretion can reflect the patient's exercise limitation and exertional dyspnea in daily life, and can also be used for the prognosis evaluation of COPD patients.
  • the measurement results are easily affected by the subject's test proficiency and auxiliary tools, which is not conducive to popularization.
  • An exercise lung function measurement system based on thoracic impedance comprising a microcontroller, a wireless communication module, a thoracic impedance measurement module and a dedicated electrode array, the thoracic impedance measurement module is respectively connected to the dedicated electrode array and the microcontroller, and the miniature control The device is connected with the wireless communication module, wherein,
  • the microcontroller invokes a pre-stored computer program to perform the following steps:
  • the thoracic impedance measurement module includes a multiplexer switch, a human body impedance measurement chip, a self-calibration circuit and a peripheral circuit, and the human body impedance measurement chip is respectively connected to the multiplexer switch, the self-calibration circuit, the peripheral circuit and the microcontroller.
  • the multiplexer switch is connected with the dedicated electrode array.
  • de-interference processing includes the following steps:
  • step 1) Subtract the signals obtained in step 1) and step 2), and perform smoothing processing to obtain a breathing signal during exercise.
  • the anti-interference processing further includes: band-pass filtering the thoracic impedance signal to extract the heart rate signal.
  • the smoothing in the steps 1) and 3) is implemented based on a five-point cubic smoothing filtering method.
  • a small-amplitude pulse signal whose threshold value is less than the set value and represents the change of thoracic impedance caused by exercise is obtained from the signal obtained in step 1) as the human body. motion signal.
  • the obtaining of local lung ventilation information and vital capacity information based on the breathing signal is specifically:
  • the local lung ventilation and vital capacity are calculated according to the impedance-pulmonary ventilation fitting formula.
  • Bioelectrical impedance technology refers to a detection technology that uses the electrical properties of biological tissues and organs and their changing laws to obtain biomedical information related to human physiological conditions. Due to the obvious differences in the electrical properties of lung tissue and gas in the lungs, the electrical impedance properties measured outside the human chest are sensitive to changes in the inflation state in the lungs. Therefore, the electrical impedance method can be used to detect changes in thoracic impedance in patients with pulmonary obstruction. This reflects the status of lung function.
  • the electrical impedance method adopted in the present invention is simple to operate, safe and reliable, portable and wearable, and the subject does not need to pass the instrument to exhale and inhale, which is more easily accepted by the subject, and the patient cooperates. It has good performance and is suitable for monitoring the pulmonary ventilation status of patients in resting state or exercise state. Therefore, it can be used as an effective supplement to routine pulmonary function tests, and has important diagnostic value and clinical significance for early screening of COPD.
  • the present invention is different from the exercise pulmonary function monitoring limited to the exercise of indoor equipment, and can monitor the pulmonary ventilation in indoor and outdoor exercise, diagnose the pulmonary function, and is convenient for use in daily exercise training, for the diagnosis of the pulmonary function. and treatment to provide reference information, with the following beneficial effects:
  • the present invention uses AFE4300 chip to measure human body impedance. Compared with the human body impedance measurement system designed and realized by separate components, the integration degree is high, the volume of the measurement system is significantly reduced, and it is easy to wear. It needs to be hard-connected to a mobile phone or computer, so that lung function measurements can be performed during running, walking and other moving processes.
  • the thoracic impedance data also includes measurement noise, motion noise, heartbeat and other information in addition to breathing information.
  • the present invention adopts band-pass filtering, wavelet filtering, five-point cubic smoothing filtering, and polynomial fitting.
  • motion noise, measurement noise, heartbeat noise, and baseline drift are removed from the measured thoracic impedance to obtain respiration-related signals, so that respiration-related thoracic impedance data can be extracted during exercise.
  • the present invention processes the breathing-related thoracic impedance signal extracted during exercise, obtains local lung ventilation information and vital capacity information during exercise, and evaluates lung function, so that lung function evaluation based on thoracic impedance characteristics can be used for exercise. Pulmonary function tests were performed during the procedure.
  • the present invention performs pulmonary function detection during non-fixed-point exercise, is wearable, has no disturbance to the subject's respiratory tract, no resistance increase, no risk of cross-infection, is more easily accepted by the subject, and is convenient for detection during daily fitness and training. use.
  • Fig. 1 is the structural schematic diagram of the pulmonary function measurement system of the present invention
  • Fig. 2 is the workflow schematic diagram of the present invention
  • Figure 3 is an example of the waveform of the original sampled thoracic impedance signal
  • Figure 4 is an example of an extracted heart rate signal
  • Figure 5 is an example of a signal after filtering and smoothing and denoising
  • Figure 7 is an example of the finally obtained signal related to human respiration.
  • this embodiment provides a thoracic impedance-based exercise pulmonary function measurement system, including a microcontroller 1, a wireless communication module 2, a thoracic impedance measurement module 3, and a dedicated electrode array 4.
  • the thoracic impedance measurement module 3 is respectively The dedicated electrode array 4 and the microcontroller 1 are connected, and the microcontroller 1 is connected with the wireless communication module 2 .
  • the dedicated electrode array 4 is in contact with the surface of the human thoracic cavity, the thoracic impedance measurement module 3 collects the measurement voltage through the dedicated electrode array 4, and the microcontroller 1 controls the thoracic impedance measurement module 3 to perform self-calibration and thoracic impedance measurement process, and compare the measured thoracic impedance.
  • Information processing obtains signals related to breathing, and then calculates the local lung ventilation status and vital capacity, and conducts lung function evaluation.
  • the evaluation results can be transmitted to external devices (such as mobile phones, computers, etc.) through the wireless communication module 2.
  • the chest impedance measurement module 3 includes a multiplexer switch 301, a body impedance measurement chip 302, a self-calibration circuit 301 and a peripheral circuit 304.
  • the body impedance measurement chip 302 is respectively connected to the multiplexer switch 301, the self-calibration circuit 301, the peripheral circuit 304 and the micro
  • the controller 1 and the multiplexer switch 301 are connected with the dedicated electrode array 4 to realize the measurement of different position information.
  • the microcontroller controls the multiplexer switch, selects different electrode pairs in turn, applies the excitation current generated by the AFE4300 to the excitation electrode pair, and transmits the response voltage to the voltage measurement channel of the AFE4300 through the multiplexer switch, and measures in sequence.
  • Four chest impedances upper left, upper right, lower left, and lower right.
  • the human body impedance measurement chip 302 adopts the AFE4300 chip; the self-calibration circuit 301 includes a precision resistor and capacitor network, which is used to calibrate the measurement performance of the AFE4300; the peripheral circuit 304 is used to provide the AFE4300 with clock signals, parameter settings, etc. .
  • the human body impedance measurement chip AFE4300 sequentially selects one of the four pairs of composite electrodes to the current excitation channel and voltage measurement channel of the AFE4300 through a multi-channel analog switch to perform impedance measurement.
  • the microcontroller 1 invokes a pre-stored computer program to execute the following steps: acquiring the thoracic impedance signal collected by the thoracic impedance measuring module 3; performing de-interference processing on the thoracic impedance signal to acquire the breathing signal during exercise; obtaining local lung ventilation based on the breathing signal Information and spirometry information to achieve lung function assessment.
  • the wireless communication module 2 adopts a Bluetooth communication module.
  • the specific measurement process of the thoracic impedance-based exercise pulmonary function measurement system includes the following steps:
  • the AFE4300 chip generates a 50kHz excitation current with an amplitude of 0.3500mA, and the current electrode pair in one of the four pairs of composite electrodes attached to the chest surface of the measured object is sequentially selected by the multiplexer switch to apply a weak current to the chest cavity of the human body. Excite the current, then measure the response voltage through the voltage electrode pair in the composite electrode, and obtain the thoracic impedance data according to the voltage/impedance fitting relationship obtained in step 1).
  • the respiration signal s 0 (n) continuously monitored during exercise is obtained by an electrical impedance measurement system with a sampling rate of 128sps, that is, 128 samples per second.
  • the original sampling signal is shown in Figure 3.
  • the normal breathing rate of adults is 12-20 breaths/min at rest, and the normal heart rate is 60-100 breaths/min, which will increase during exercise.
  • the thoracic impedance signal is subjected to wavelet filtering and smoothing, and the baseline drift is removed by polynomial fitting.
  • the most general model of a measurement signal has the form:
  • the smoothing used is a five-point cubic smoothing filtering method.
  • the five-point cubic smoothing filter is a low-pass filter that uses polynomial least squares approximation to smooth the sampling points.
  • the algorithm is as follows:
  • a polynomial fitting method is used to remove the baseline drift.
  • a polynomial fit is performed on a signal with a linear trend to obtain a fitted baseline, and then the baseline-fitted signal is subtracted from the original signal to obtain a signal with baseline drift removed.
  • the present invention adopts the method of combining the above-mentioned wavelet threshold filtering and the five-point cubic smoothing method, which can effectively filter out high-frequency noise interference and maintain the reconstructed breathing signal to obtain a higher signal-to-noise ratio.
  • the wavelet threshold filtering adopts a fixed hard threshold, which is adjusted according to the noise level estimation of the first layer of wavelet decomposition.
  • the five-point cubic smoothing filter coefficient is 5, that is, 5 iterations are performed. At the same time, there is a certain baseline drift phenomenon in the measured signal.
  • Threshold judgment is performed on the amplitude and slope changes of the obtained signal, and the human motion signal is extracted.
  • the thoracic impedance value measured by the electrical impedance measurement system will change due to muscle movement and changes in the position of the diaphragm.
  • the change of electrical impedance value caused by the change of air content in the lung is usually 2-10 ⁇ when the human body is breathing calmly, and the change of electrical impedance value caused by the change of air content in the lung during deep breathing is usually 5-20 ⁇ .
  • the amplitude is small, usually below 2 ⁇ , and the increase and decrease are faster and the frequency is higher, which appears as a small-amplitude pulse signal superimposed on the breathing signal. Therefore, the resistance change s 3 (n) caused by the movement of the human body can be judged and extracted according to the threshold value and slope of the amplitude change, as shown in FIG. 6 .
  • Subtracting s 2 (n) from s 3 (n) followed by a five-point cubic smoothing filter yields a breathing signal s 4 (n) that reflects lung ventilation conditions, as shown in FIG. 7 .
  • a breathing signal s 4 (n) that reflects lung ventilation conditions, as shown in FIG. 7 .

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Abstract

一种基于胸阻抗的运动肺功能测量系统，包括微型控制器（1）、无线通信模块（2）、胸阻抗测量模块（3）和专用电极阵列（4），胸阻抗测量模块（3）分别连接专用电极阵列（4）和微型控制器（1），微型控制器（1）与无线通信模块（2）连接，其中，微型控制器（1）调用预存储的计算机程序执行以下步骤：获取胸阻抗测量模块（3）采集的胸阻抗信号；对胸阻抗信号进行去干扰处理，获取运动过程中的呼吸信号；基于呼吸信号获得局部肺通气信息和肺活量信息，实现肺功能评估。与现有技术相比，具有可有效克服干扰、准确性高、适于运动状态检测、对呼吸道无扰动的优点。

Description

一种基于胸阻抗的运动肺功能测量系统 技术领域
本发明涉及医疗检测领域，尤其是涉及一种基于胸阻抗的运动肺功能测量系统。
背景技术
慢性阻塞性肺疾病(COPD)是一种常见的呼吸系统慢性疾病，作为一个重要的公共卫生问题，其早期诊断方法依赖于肺功能筛查，使用肺量计进行肺功能检查被认为是金标准，在吸入支气管舒张剂后，第一秒用力呼气容积(FEV1)/用力肺活量(FVC)＜70％表明存在气流受限，并且不能完全逆转。但基于肺量计的肺功能筛查普及率有限，加上肺的代偿能力强大，85％的COPD患者确诊前5年已经患病，多数患者确诊时肺功能已经损失50％以上，开发新的肺功能检测方法筛查慢阻肺，实现慢阻肺的早发现早治疗，对于控制慢阻肺的影响、提高患者生活质量具有重要意义。
由于运动增加了人体氧的消耗量，运动状态下更容易发现慢阻肺的早期病变。心肺运动试验(CPET)是目前国际上普遍使用的衡量人体呼吸和循环机能水平的肺功能检查之一，它可用于功能性运动容量的评价、疾病的诊断及判断治疗。不同于静态肺功能检查仅反映静息状态下的通气或换气状况，CPET首先在静息状态下测定人体的全套肺功能之后,在不同负荷下连续动态监测记录进出气流、氧气和二氧化碳,实时检测机体氧耗量和二氧化碳排出量等参数的动态变化，能够反映患者在日常生活中的运动受限和劳力性呼吸困难情况，另外也可用于COPD患者的预后评估。但由于CPET成本较高并需专门的设备和专业的操作人员，测量结果易受受试者测试熟练程度及辅助工具的影响，不利于普及推广。
发明内容
本发明的目的就是为了克服上述现有技术存在的缺陷而提供一种可有效克服干扰、准确性高、适于运动状态检测、对呼吸道无扰动的基于胸阻抗的运动 肺功能测量系统。
本发明的目的可以通过以下技术方案来实现：
一种基于胸阻抗的运动肺功能测量系统，包括微型控制器、无线通信模块、胸阻抗测量模块和专用电极阵列，所述胸阻抗测量模块分别连接专用电极阵列和微型控制器，所述微型控制器与无线通信模块连接，其中，
所述微型控制器调用预存储的计算机程序执行以下步骤：
获取胸阻抗测量模块采集的胸阻抗信号；
对所述胸阻抗信号进行去干扰处理，获取运动过程中的呼吸信号；
基于所述呼吸信号获得局部肺通气信息和肺活量信息，实现肺功能评估。
进一步地，所述胸阻抗测量模块包括多路转换开关、人体阻抗测量芯片、自校正电路和外围电路，所述人体阻抗测量芯片分别连接多路转换开关、自校正电路、外围电路和微型控制器，所述多路转换开关与专用电极阵列连接。
进一步地，所述人体阻抗测量芯片采用AFE4300芯片。
进一步地，所述去干扰处理包括以下步骤：
1)对所述胸阻抗信号进行小波滤波和平滑处理，并用多项式拟合法去除基线漂移；
2)对步骤1)所得信号的幅值变化的阈值和斜率，提取人体运动信号；
3)将步骤1)与步骤2)所得的信号相减，并做平滑处理，得到运动过程中的呼吸信号。
进一步地，所述去干扰处理还包括：对所述胸阻抗信号进行带通滤波，提取心率信号。
进一步地，基于巴特沃斯滤波器的带通滤波器实现所述带通滤波。
进一步地，所述步骤1)和步骤3)中的平滑处理基于五点三次平滑滤波方法实现。
进一步地，所述步骤2)中，基于幅值变化的阈值和斜率，从步骤1)所得信号中获得阈值小于设定值的、表征运动产生的胸阻抗变化的小幅脉冲信号，作为所述人体运动信号。
进一步地，所述基于所述呼吸信号获得局部肺通气信息和肺活量信息具体为：
以所述呼吸信号作为准确胸阻抗信号，根据阻抗-肺通气量拟合公式，计算局部肺通气量和肺活量。
进一步地，所述无线通信模块采用蓝牙通信模块。
生物电阻抗技术是指利用生物组织、器官等的电特性及其变化规律，获取人体生理状况相关的生物医学信息的检测技术。由于肺脏组织及肺内气体的电特性具有明显的差异，通过人体胸外测量到的电阻抗特性对肺内充气状态的变化敏感，因此可以通过电阻抗方法对肺阻塞患者胸阻抗变化进行检测，从而反映肺功能状况。与传统气流式肺量计相比，本发明采用的电阻抗法操作简单，安全可靠，便携可穿戴，受测者不需要经过仪器进行呼气和吸气更容易被受测者接受，患者配合性好，适用于患者静息状态或者运动状态下的肺通气状况监测，因此可以作为常规肺功能检查的有效补充，对于COPD早期筛查具有重要的诊断价值和临床意义。
与现有技术相比，本发明不同于局限于室内器械运动的运动肺功能监测，可以在室内外运动中监测肺通气情况，诊断肺功能，方便在日常运动训练中使用，为肺功能的诊断及治疗提供参考信息，具有如下有益效果：
1、本发明采用AFE4300芯片测量人体阻抗，相比分离元件设计实现的人体阻抗测量系统集成度高、测量系统体积显著降低、便于穿戴；通过蓝牙发送肺功能评估结果到手机或者电脑等设备，不需要与手机或者电脑硬连接，从而可以在跑步、步行等移动过程中进行肺功能测量。
2、本发明采用精密电阻电容对AF4300进行校准，克服不同芯片性能之间的差异及同一芯片性能的漂移，实现高精度胸阻抗测量。
3、由于在运动过程中测量，胸阻抗数据除呼吸信息之外还包含了测量噪声、运动噪声、心跳等信息，本发明采用带通滤波、小波滤波、五点三次平滑滤波、多项式拟合等数据处理过程，从测量到的胸阻抗中去除运动噪声、测量噪声、心跳噪声、基线漂移，获得呼吸相关的信号，从而可以在运动过程中提取与呼吸相关的胸阻抗数据。
4、本发明对运动过程中提取的与呼吸相关的胸阻抗信号进行处理，得到运动过程中的局部肺通气信息和肺活量信息，评估肺功能，使得基于胸阻抗特征的肺功能评估可以用于运动过程中肺功能检测。
5、本发明在非定点运动过程中进行肺功能检测，可穿戴，对受测者呼吸道无扰动无阻力增加，无交叉感染风险，更容易被受测者接受，便于日常健身、训练过程中检测使用。
6、本发明在人体氧需求量增加的运动过程中检测肺通气状况，有助于发现肺功能的早期下降，便于早期筛查发现COPD症状，实现COPD的早诊早治。
附图说明
图1为本发明肺功能测量系统的结构示意图；
图2为本发明的工作流程示意图；
图3为原始采样胸阻抗信号波形图示例；
图4为提取出的心率信号示例；
图5为滤波和平滑去噪处理后的信号示例；
图6为阈值判断提取出的人体运动信号示例；
图7为最终获得的与人体呼吸相关的信号示例。
具体实施方式
下面结合附图和具体实施例对本发明进行详细说明。本实施例以本发明技术方案为前提进行实施，给出了详细的实施方式和具体的操作过程，但本发明的保护范围不限于下述的实施例。
实施例1
如图1所示，本实施例提供一种基于胸阻抗的运动肺功能测量系统，包括微型控制器1、无线通信模块2、胸阻抗测量模块3和专用电极阵列4，胸阻抗测量模块3分别连接专用电极阵列4和微型控制器1，微型控制器1与无线通信模块2连接。专用电极阵列4与人体胸腔表面接触，胸阻抗测量模块3通过专用电极阵列4采集测量电压，微型控制器1控制胸阻抗测量模块3进行自校正和胸阻抗测量过程，并将测量到的胸阻抗信息处理获得与呼吸相关的信号，进而计算得到局部肺通气状况、肺活量，进行肺功能评估，评估结果可通过无线通信模块2向外部设备(如手机、电脑等)传输。
本实施例中，专用电极阵列4包括8个专用复合电极贴附于胸腔表面，前 胸上下左右4个电极，后背与之相对贴附有4个电极，前胸与后背相对的电极构成电极对，4对电极分别测量左上、右上、左下、右下4个胸阻抗；每一个复合电极包含同心但绝缘的两个电极，外侧的大电极用于施加激励电流，内侧的小电极用于测量响应电压。通过上述复合电极中的电流电极施加激励电流、通过复合电极中的电压电极检测响应电压，在芯片内部进行信号调理和模数转换，获得测量电压。
胸阻抗测量模块3包括多路转换开关301、人体阻抗测量芯片302、自校正电路301和外围电路304，人体阻抗测量芯片302分别连接多路转换开关301、自校正电路301、外围电路304和微型控制器1，多路转换开关301与专用电极阵列4连接，实现不同位置信息的测量。测量时，由微控制器控制多路转换开关，依次选择不同的电极对，将AFE4300产生的激励电流施加到激励电极对，将响应电压经由多路选择开关传送到AFE4300的电压测量通道，依次测量左上、右上、左下、右下4个胸阻抗。
胸阻抗测量模块3中，人体阻抗测量芯片302采用AFE4300芯片；自校正电路301包括精密电阻和电容网络，用于对AFE4300测量性能进行标定；外围电路304用于为AFE4300提供时钟信号、参数设置等。人体阻抗测量芯片AFE4300通过多路模拟开关依次选通四对复合电极中的一对到AFE4300的电流激励通道和电压测量通道，进行阻抗测量。
微型控制器1调用预存储的计算机程序执行以下步骤：获取胸阻抗测量模块3采集的胸阻抗信号；对胸阻抗信号进行去干扰处理，获取运动过程中的呼吸信号；基于呼吸信号获得局部肺通气信息和肺活量信息，实现肺功能评估。
本实施例中，无线通信模块2采用蓝牙通信模块。
该基于胸阻抗的运动肺功能测量系统的具体测量过程包括以下步骤：
1)利用自校准电路对AFE4300芯片进行校准，获得测量到电压数据与被测阻抗之间的拟合关系。
2)AFE4300芯片产生50kHz激励电流，幅值为0.3500mA，通过多路选择开关依次选通贴附于被测对象胸腔表面的四对复合电极中的一对中的电流电极对对人体胸腔施加微弱激励电流，然后通过复合电极中的电压电极对测量响应电压，根据步骤1)得到的电压/阻抗拟合关系，获得胸阻抗数据。采用电阻 抗测量系统获得运动时连续监测的呼吸信号s 0(n)，采样率为128sps，即每秒钟采样128个，原始采样信号如图3所示。成年人在安静时正常呼吸次数是12-20次/分，正常心率为60-100次/分，运动时均会增加。
3)对胸阻抗信号进行基于巴特沃斯滤波器的带通滤波器，提取心率信号s 1(n)，用于运动过程中心率监测，心率可以用于运动强度的评估，防止运动过度，如图4所示。
4)对胸阻抗信号进行小波滤波和平滑处理，并用多项式拟合法去除基线漂移。具体地，测量信号的最通用模型具有以下形式：
s(n)＝f(n)+e(n)        (1)
其中时间n等距。去噪的目的是抑制信号s(n)的噪声部分e(n)并恢复有用信号f(n)。其原理是，信号在空间上(或者时间域)是有一定连续性的，在小波域有效信号所产生的小波系数其模值往往较大；而高斯白噪声在空间上(或者时间域)是没有连续性的，噪声经过小波变换在小波域仍然表现为很强的随机性，仍满足高斯白噪声分布。在小波域中，若噪声的小波系数对应的方差为σ，根据高斯分布的特性，绝大部分噪声系数都位于[-3σ，3σ]区间内。因此，只要将区间[-3σ，3σ]内的系数置零，就能最大程度抑制噪声，同时保留有效信号。将经过阈值处理后的小波系数重构，就可以得到去噪后的有用信号。
使用的平滑处理是五点三次平滑滤波方法。五点三次平滑滤波是一种低通滤波器，利用多项式最小二乘逼近来对采样点实行平滑滤波，其算法如下：
设已知n(n≥5)个等距点的观测值为x 0<x 1<…<x n-1，则可以在每个数据点前后各取两个相邻点，通过三次多项式进行逼近：
y＝a 0+a 1x+a 2x 2+a 3x 3      (2)
根据最小二乘原理，可确定出a 0，a 1，a 2，a 3，最后得到五点三次平滑公式如下：
Figure PCTCN2021120106-appb-000001
最后采用多项式拟合法去除基线漂移。首先对含有线性趋势的信号进行多项式拟合得到拟合的基线，然后从原始信号中减去基线拟合信号，可得到去除基线漂移的信号。
为了提取呼吸信号，需要将人体心率信号及环境引入的高频噪声滤除掉。本发明采用上述小波阈值滤波与五点三次平滑法相结合的方法，能够有效滤除高频噪声干扰并保持重构呼吸信号，获得较高的信噪比。其中，小波阈值滤波采用固定式硬阈值，根据第一层小波分解的噪声水平估计进行调整。五点三次平滑滤波器系数为5，即进行5次迭代。同时，测得信号存在一定的基线漂移现象，通过多项式拟合的方法，一般对含有线性趋势的信号进行三次多项式拟合得到拟合的基线，然后从原始信号中减去拟合信号，可得到去除基线的信号s 2(n)，如图5所示。
5)对所得信号幅值及斜率变化进行阈值判断，提取人体运动信号。
当人体进行步行或跑步运动时，由于肌肉运动以及膈肌位置变化，电阻抗测量系统测得的胸阻抗值会随之发生变化。人体平静呼吸时肺内含气量改变引起的电阻抗值变化通常为2-10Ω，深呼吸时肺内含气量改变引起的电阻抗值变化通常为5-20Ω，与其相比，运动产生的胸阻抗变化幅值较小，通常在2Ω以下，且增减更快，频率更高，呈现为叠加在呼吸信号上的小幅脉冲信号。因此，可以根据幅值变化的阈值和斜率，判断和提取出人体运动引入的阻值变化s 3(n)，如图6所示。
6)将步骤4)与步骤5)所得的信号相减，并做平滑处理，得到呼吸信号。
将s 2(n)减去s 3(n)然后使用五点三次平滑滤波，得到反映了肺通气状况的呼吸信号s 4(n)，如图7所示。通过对可对人体运动过程中的肺通气状况做出判断，从而为肺功能诊断提供依据。
7)对呼吸信号s 4(n)进行特征分析，得到局部肺通气信息和肺活量信息，评估肺功能。
8)返回步骤1)直到运动结束或者收到结束测量指令。
9)通过蓝牙发送肺功能实时评估结果到手机或者电脑等设备。
以上详细描述了本发明的较佳具体实施例。应当理解，本领域的普通技术人员无需创造性劳动就可以根据本发明的构思作出诸多修改和变化。因此，凡 本技术领域中技术人员依本发明的构思在现有技术的基础上通过逻辑分析、推理或者有限的实验可以得到的技术方案，皆应在由权利要求书所确定的保护范围内。

Claims (10)

  1. 一种基于胸阻抗的运动肺功能测量系统，其特征在于，包括微型控制器(1)、无线通信模块(2)、胸阻抗测量模块(3)和专用电极阵列(4)，所述胸阻抗测量模块(3)分别连接专用电极阵列(4)和微型控制器(1)，所述微型控制器(1)与无线通信模块(2)连接，其中，
    所述微型控制器(1)调用预存储的计算机程序执行以下步骤：
    获取胸阻抗测量模块(3)采集的胸阻抗信号；
    对所述胸阻抗信号进行去干扰处理，获取运动过程中的呼吸信号；
    基于所述呼吸信号获得局部肺通气信息和肺活量信息，实现肺功能评估。
  2. 根据权利要求1所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述胸阻抗测量模块(3)包括多路转换开关(301)、人体阻抗测量芯片(302)、自校正电路(301)和外围电路(304)，所述人体阻抗测量芯片(302)分别连接多路转换开关(301)、自校正电路(301)、外围电路(304)和微型控制器(1)，所述多路转换开关(301)与专用电极阵列(4)连接。
  3. 根据权利要求2所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述人体阻抗测量芯片(302)采用AFE4300芯片。
  4. 根据权利要求1所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述去干扰处理包括以下步骤：
    1)对所述胸阻抗信号进行小波滤波和平滑处理，并用多项式拟合法去除基线漂移；
    2)对步骤1)所得信号的幅值变化的阈值和斜率，提取人体运动信号；
    3)将步骤1)与步骤2)所得的信号相减，并做平滑处理，得到运动过程中的呼吸信号。
  5. 根据权利要求4所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述去干扰处理还包括：对所述胸阻抗信号进行带通滤波，提取心率信号。
  6. 根据权利要求5所述的基于胸阻抗的运动肺功能测量系统，其特征在于，基于巴特沃斯滤波器的带通滤波器实现所述带通滤波。
  7. 根据权利要求4所述的基于胸阻抗的运动肺功能测量系统，其特征在于， 所述步骤1)和步骤3)中的平滑处理基于五点三次平滑滤波方法实现。
  8. 根据权利要求4所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述步骤2)中，基于幅值变化的阈值和斜率，从步骤1)所得信号中获得阈值小于设定值的、表征运动产生的胸阻抗变化的小幅脉冲信号，作为所述人体运动信号。
  9. 根据权利要求1所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述基于所述呼吸信号获得局部肺通气信息和肺活量信息具体为：
    以所述呼吸信号作为准确胸阻抗信号，根据阻抗-肺通气量拟合公式，计算局部肺通气量和肺活量。
  10. 根据权利要求1所述的基于胸阻抗的运动肺功能测量系统，其特征在于，所述无线通信模块(2)采用蓝牙通信模块。
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