Monitoring Of Lung Ventilation Research Articles

Application of electrical impedance tomography imaging technology combined with generative adversarial network in pulmonary ventilation monitoring

Electrical impedance tomography (EIT) plays a crucial role in the monitoring of pulmonary ventilation and regional pulmonary function test. However, the inherent ill-posed nature of EIT algorithms results in significant deviations in the reconstructed conductivity obtained from voltage data contaminated with noise, making it challenging to obtain accurate distribution images of conductivity change as well as clear boundary contours. In order to enhance the image quality of EIT in lung ventilation monitoring, a novel approach integrating the EIT with deep learning algorithm was proposed. Firstly, an optimized operator was introduced to enhance the Kalman filter algorithm, and Tikhonov regularization was incorporated into the state-space expression of the algorithm to obtain the initial lung image reconstructed. Following that, the imaging outcomes were fed into a generative adversarial network model in order to reconstruct accurate lung contours. The simulation experiment results indicate that the proposed method produces pulmonary images with clear boundaries, demonstrating increased robustness against noise interference. This methodology effectively achieves a satisfactory level of visualization and holds potential significance as a reference for the diagnostic purposes of imaging modalities such as computed tomography.

The Role of Electrical Impedance Tomography for Management of High-Risk Pulmonary Embolism in a Postoperative Patient.

Electrical impedance tomography (EIT) is a non-invasive, radiation-free and bedside imaging tool that is widely used for real-time monitoring of lung ventilation. Recently, it has been proposed for use in quantitative assessment of regional lung perfusion with hypertonic saline bolus injection and consequently for pulmonary embolism (PE) detection. Here, we present a case of high-risk PE in a postoperative patient, in which EIT monitoring provided us with useful information for diagnosis and decision-making, especially with the challenge of anticoagulation and risk of bleeding.

A Wireless, Low-Power, and Miniaturized EIT System for Remote and Long-Term Monitoring of Lung Ventilation in the Isolation Ward of ICU

Individualized lung-protective ventilation strategy is essential for patients with COVID-19. In this study, a wireless, low-power, and miniaturized electrical impedance tomography (EIT) system was developed for remote and long-term monitoring of lung ventilation for patients with COVID-19 in the isolation ward of ICU. A new strategy of combining filtering and improved voltage-controlled current was employed to design the current source for a simplified system structure, and a new differential receiver circuit consisting of a buffer amplification and a differential amplification was proposed to design the voltage measurement unit for high precision. Moreover, a Bluetooth interface was adopted for wireless data transmission, and components characterized by low power consumption were selected to minimize the system power consumption. The proposed EIT system occupies a total size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.5\times 4.5\times0.6$ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and can work stably within 25 m from the wireless terminal installed with host EIT software. The system has a signal-to-noise of 70 dB at 50 kHz, stability of 0.1% relative change, and power consumption of 114 mW, as tested with a resistor phantom. Furthermore, a comparison between the proposed system and a commercial ICU EIT device was conducted on nine healthy volunteers for ventilation monitoring. The correlation between lung volume and relative impedance changes was higher than 0.9 for both EIT systems ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p &lt; 0.001$ </tex-math></inline-formula> ). The analysis of the corresponding EIT images revealed that both systems delivered comparable images in terms of linearity, repeatability, and regional ventilation distribution. The test and experimental results suggested that the proposed system could conveniently provide reliable data acquisition (DAQ) for remote and long-term lung ventilation monitoring.

Influence of current injection scheme on electrical impedance tomography for monitoring of the respiratory function of obese subjects

Electrical impedance tomography (EIT) has been proposed as a noninvasive radiation-free functional imaging modality for bedside monitoring of lung ventilation. Due to the intrinsic low sensitivity of measured boundary voltages with respect to internal conductivity changes, EIT image reconstructions are more challenging for the regions that are located deeper from the attached surface electrodes. Considering the worldwide prevalence of obesity, it is highly desirable for an EIT system to produce high-quality images from obese as well as lean subjects. In EIT, the internal current density distribution and the sensitivity of a boundary voltage to a change of internal conductivity vary with respect to the current injection scheme. We quantified the range of measured boundary voltages subject to a chosen current injection scheme and investigated the influence of various obesity levels on the number of distinguishable boundary voltages given a fixed amount of system noise. We found that the 0-skip current injection scheme, where neighboring electrode pairs are used for current injections, could be most favorable to improve spatial resolution but produces the smallest number of distinguishable boundary voltages. To obtain an enough number of distinguishable boundary voltages from an obese subject, the gap between current injection electrodes should be increased depending on the circumference of a chosen imaging plane. We suggested a guideline for current injection schemes in EIT to produce images with better quality from obese as well as lean subjects.

Lung monitoring with electrical impedance tomography: technical considerations and clinical applications.

In recent years there has been substantial progress in the imaging evaluation of patients with lung disease requiring mechanical ventilatory assistance. This has been demonstrated by the inclusion of pulmonary ultrasound, positron emission tomography, electrical impedance tomography (EIT), and magnetic resonance imaging (MRI). The EIT uses electric current to evaluate the distribution of alternating current conductivity within the thoracic cavity. The advantage of the latter is that it is non-invasive, bedside radiation-free functional imaging modality for continuous monitoring of lung ventilation and perfusion. EIT can detect recruitment or derecruitment, overdistension, variation of poorly ventilated lung units (silent spaces), and pendelluft phenomenon in spontaneously breathing patients. In addition, the regional expiratory time constants have been recently explored.

Lung ventilation monitoring by electrical bioimpedance technique using three different 4-electrode thoracic configurations: Variability of calibration equations

Abstract Our research group proposes the use of electrical bioimpedance (BE) technique to monitor the ventilatory pattern. The objective of this study was to obtain a set of calibration equations in a group of males (M:23) and females (F:22) and analyze the variability of their mathematical adjustments (R2). All equations are aimed to adjust the impedance changes (IC) due to ventilation and transform them into a measurable volume signal. The IC were obtained by three 4-electrode configurations, where, the current injection electrodes were placed in different points around the sixth intercostal space and the voltage detection electrodes were placed in different points around the second intercostal space. All impedance determinations were validated by a pneumotachometer (gold-standard). The calibration equations were obtained from a multivariate analysis of the proportionality coefficients of volume and impedance signals; and the anthropometric parameters of each group of volunteers. The obtained results evidenced that just two sets of equations determined by one configuration had a high mathematical adjustment of 66% and 70% in the group of males and females, respectively. From the validation of these equations, errors of 22%±3% and 15%±3% in the group of males and females, respectively, were evidenced. The variability of errors was significant, however, the analysis of differences between them was not. We conclude that the variability of calibration equations depends on the variability of anthropometric parameters and the amplitudes of impedance changes which are determined by the anatomic spots where the electrodes were placed.

The role of electrical impedance tomography for monitoring during bronchoscopy: A case report

Continuous monitoring of lung ventilation can be useful in treating patients admitted to the intensive care unit (ICU). Electrical impedance tomography (EIT) has been used as a relatively new imaging technique for this purpose. We presented a patient with pneumonia who was admitted to the ICU after pulmonary thromboembolism (PTE) required to perform bronchoalveolar lavage (BAL). A drainage procedure and subsequent improvement in pulmonary function were monitored using EIT contributed to the treatment process. The patient has been discharged from the hospital with an improved general condition.

A 1.4-m $\Omega$ -Sensitivity 94-dB Dynamic-Range Electrical Impedance Tomography SoC and 48-Channel Hub-SoC for 3-D Lung Ventilation Monitoring System

A wearable electrical impedance tomography (EIT) system is proposed for the portable real-time 3-D lung ventilation monitoring. It consists of two types of SoCs, active electrode (AE)-SoC and Hub-SoC, mounted on wearable belts. The 48-channel AE-SoCs are integrated on flexible printed circuit board belt, and Hub-SoC is integrated in the hub module which performs data gathering and wireless communication between an external imaging device. To get high accuracy under the variation of conductivity, the dual-mode current stimulator provides the optimal frequency for time difference-EIT and frequency difference-EIT with simultaneous 4 k–128 kHz impedance sensing. A wide dynamic range instruments amplifier is proposed to provide 94 dB of wide dynamic range impedance sensing. In addition, the 48-channel AE system with the dedicated communication and calibration is implemented to achieve 1.4- $\text{m}\Omega $ sensitivity of impedance difference in the in vivo environment. The AE-/Hub-SoCs occupy 3.2 and 1.3 mm2 in 65-nm CMOS technology and consume $124~\mu \text{W}$ and 1.1 mW with 1.2 V supply, respectively. As a result, EIT images are reconstructed with 90% of accuracy, and up to 10 frames/s real-time 3-D lung images are successfully displayed.

Electrical impedance tomography for lung ventilation monitoring of the dog.

Electrical impedance tomography (EIT) is a radiation free technique which takes advantage of the different electrical conductivities of different tissues. Its main field of application is lung ventilation monitoring. The aim of this prospective study was to evaluate the feasibility of collecting EIT information on a sample of dogs with different thoracic shapes under clinical conditions by connecting an electrode belt without fur clipping. Fifteen pulmonary healthy dogs were anaesthetized, positioned in sternal recumbency and ventilated in a pressure-controlled mode at three different positive end-expiratory pressure levels (PEEP) of 0, 5 and 10cmH2O for five breaths each, with a peak inspiratory pressure of 15cmH2O. The impedance changes were recorded with a commercial EIT device applied around the thorax. Subsequently, the ventilation regime was repeated and a computed tomography scan (CT) of the same thoracic segment was performed for each PEEP level. The tidal volume (Vt) was recorded. For the collection of EIT data the sum of regional impedance changes was recorded. The impedance value of the entire lung (global) was recorded and the ventilated area was quartered into four regions of interest (ROI). In a CT image with the fewest adjacent organs, lung tissue was selected to obtain the mean value of lung radiodensitiy in Hounsfield-Units (HU) for the entire lung and for the four ROIs. EIT recordings via the electrode belt were possible without clipping. There was a significant correlation for the parameters of aeration as measured by EIT and CT for both the entire ventilated lung and the corresponding ROIs. The increasing PEEP resulted in a proportional increase of the impedance, and there was a negative correlation between EIT and Vt. The better ventilated dorsal ROIs could be identified using both EIT and CT. An intra-assay coefficient of variation showed a good reproducibility for lung ventilation in anaesthetized dogs in the EIT. The results show that EIT is a reliable method for evaluating the ventilation of dogs in a clinical setting. The accuracy of EIT might be improved by using a mesh corresponding to the different thoracic shapes of the dogs.

A 10.4 mW Electrical Impedance Tomography SoC for Portable Real-Time Lung Ventilation Monitoring System

An electrical impedance tomography (EIT) SoC is proposed for the portable real-time lung ventilation monitoring system. The proposed EIT SoC is integrated into belt-typefabric system with 32 electrodes and can show the dynamic images of the lung ventilation on the mobile devices. To get high fidelity images, a T-switch is adopted for high off-isolation between electrodes more than 60 dB, and I/Q signal generation and demodulation can obtain both real and imaginary part of images. For the real-time imaging, an on-chip fast demodulation scheme is proposed, and it can also reduce speed requirements of ADC for low-power consumption. The proposed EIT SoC of 5.0 mm × 5.0 mm is fabricated in 0.18 µm CMOS technology, and consumes only 10.4 mW with 1.8 V supply. As a result, EIT images were reconstructed with 97.3% of accuracy and up to 20 frames/s real-time lung images can be displayed on the mobile devices.

Tidal volume monitoring by electrical impedance tomography (EIT) using different regions of interest (ROI): Calibration equations

A set of calibration equations was previously obtained to transform the lung impedance changes obtained by electrical impedance tomography (EIT), using all frame's elements, into a measurable volume signal. In order to study the goodness of the use of regions of interest (ROI) for lung ventilation monitoring, we considered 6 different ROI to obtain a calibration equation for each area. Our aim was to compare the results, determined by these areas, and those obtained by using all EIT image elements. Two ROI's were defined by those pixels with an impedance change higher than 30% and 70% of the maximum change value. These areas were called P30 and P70, respectively. Two other ROI were defined by bounding two areas by mouse, resembling P30 and P70 regions, which were called M30 and M70, respectively. The remainder was defined by two elliptical areas with an eccentricity of 0.8, and 25 and 32 pixels of mayor axis (E25p and E32p, respectively). Twenty healthy males and 24 chronic obstructive pulmonary disease (COPD) patients were considered. For small region (P30 and M30) we obtained a large dispersion in volume measurement, concluding that small regions are not suitable for monitoring the tidal changes in lung volume even for healthy subjects. The results obtained by the remainder areas, and by using EIT image were similar. Even a slight improvement in data dispersion was obtained by using some ROI. These optimal results, for healthy people, were those corresponding to P70 and M70 (volume dispersion improved from 12% with the whole EIT image to 9% using ROI), and for COPD patients improves volume dispersion from 32% using the whole EIT image to 27% by using E25p. Using not so small ROI, it is possible to estimate the total lung ventilation.

Applications of the bi-layer thin film sensor system for registering cardio-respiratory activity

A novel bi-layer thin film sensor system was used for accurately registering physiological parameters associated with body movements, such as cardiac and respiratory activities. The bi-layer curvature sensor system can provide additional medical information about the cardiac activity of the patient by mapping the five characteristic waves of the normal heartbeat rate (P, Q, R, S and T wave). This system was also used for registering physiological parameters such as the monitoring of lung ventilation which can give a range of information about the patients health (normal respiration patterns, deep inhalation/exhalation and apnoea), easily distinguishable in the output signal. The bi-layer thin films used consist of a magnetic layer and a non-magnetic counter layer that is utilized to enhance the changes in the relative permeability of the material caused by tensile or compressive stresses during bending. The measuring system is based on a personal computer in conjunction with the LabVIEW ® graphical programming package. The nature of this configuration provides the necessary features for sensor signal acquisition, analysis and data presentation. The results from the sensor application on patients demonstrate that this system can provide a robust, cost effective solution to monitoring cardio-respiratory activity with minimum inconvenience to the patient, which is necessary for prolonged, undisturbed monitoring.