Ultrasonic Parameters Research Articles

Orthogonal experiments and bonding analysis of ultrasonic welded multi-layer battery foils and tabs

The motivation for this research stems from the growing demand for solid-phase welding technology to join multilayers metals, particularly in green electric vehicles. Welding of foils and tabs inside battery is a challenging task due to poor joint formation at the interface and low strength. Ultrasonic welding is an efficient, reliable and environmentally friendly bonding method to firmly connect multi-layer copper foils and tabs. Therefore, this is used to achieve electrical bonding within the lithium-ion batteries. This is widely used in production of new energy vehicle batteries. In this work, 40 layers of copper foil were bonded to 0.3 mm nickel-plated copper tabs using ultrasonic metal welding technology. The effect of ultrasonic welding parameters on T-peel strength of joints was systematically investigated by orthogonal experimental design. The maximum T-peel strength of 359.17 N was obtained under optimal parameters (e.g., welding energy 600 J, pressure 0.3 MPa and amplitude 55 %). The variation of welding temperature and amplitude under different welding parameters was measured using infrared thermometer and laser vibrometer. Moreover, the surface, cross-sectional and failure fracture analysis and characterization of specimens with different weld qualities were performed using optical microscopy and scanning electron microscopy (SEM). In addition, the state of Ni layer in cross-section was analyzed using the energy dispersive spectroscopy (EDS) technique after ultrasonic welding. This approach can be straightforward and more appropriate to the development of solid-phase welding method for automotive industry.

A numerical investigation of longitudinal wave for thermo-acoustoelastic effects on fluid-embedded in two viscoelastic layer plates at higher temperatures

Ultrasound has become indispensable for inspecting complex structures due to its efficient propagation in both liquids and solid materials. Extensive research has been conducted across various domains, encompassing wave behavior, structural interactions, material dispersion due to heterogeneity, propagation characteristics near boundaries, defect detection, and signal processing. In this context, longitudinal waves are particularly favored for examining thick components exhibiting surface defects or thermal gradients across their depth. In our current work, we employed a numerical approach based on the Transfer Matrix Method (TMM) to model ultrasound signals backscattered under normal incidence by a multilayer structure immersed in water. This method involves representing each layer using a quadrupole formalism that combines stresses and velocities. Simultaneously, we harnessed the thermodynamic equation for aqueous solutions and Fourier’s law to derive the expression for the thermo-acoustic coefficient of longitudinal waves within a fluid embedded between two parallel immersed plates, enabling precise control of the fluid temperature over a range from 0 °C to 700 °C. In the time domain, we evaluated the ultrasonic parameters of a fluid exposed to a temperature range from 0 to 700 °C. This evaluation was supported by a variety of multilayer structures designed to ensure the accurate processing of backscattered signals. These structures were excited by longitudinal waves, with a central frequency fixed at 5 MHz. The results obtained emphasize the sensitivity of longitudinal waves to temperature variations and reveal the presence of wave dispersion induced by temperature fluctuations. In order to investigate this dispersion, we conducted an extensive study of ultrasonic longitudinal wave propagation across a range of excitation frequencies from 2 to 12 MHz. This study encompassed the calculation of phase and group velocities, as well as the corresponding attenuation. The results confirm the relevance of our research to various applications and highlight the complex interaction between longitudinal wave dispersion and temperature variations.

Relationship between Cephalometric and Ultrasonic Airway Parameters in Adults with High Risk of Obstructive Sleep Apnea.

Background/Objectives: Polysomnography and cephalometry have been used for studying obstructive sleep apnea (OSA) etiology. The association between craniofacial skeleton and OSA severity remains controversial. To study OSA's etiology, cephalometry, fiberoptic pharyngoscopy, polysomnography, and sleep endoscopy have been used; however, airway obstructions cannot be located. Recent research suggested ultrasonography for OSA screening and upper airway obstruction localization. Thus, this study aims to investigate the relationship between specific craniofacial cephalometric and ultrasonic airway parameters in adults at high risk of OSA. Methods: To assess craniofacial structure, lateral cephalograms were taken from thirty-three adults over 18 with a STOP-Bang questionnaire score of three or higher and a waist-to-height ratio (WHtR) of 0.5 or higher. Airway parameters were assessed through submental ultrasound. Results: NSBA correlated with tongue base airspace width, while MP-H correlated with oropharynx, tongue base, and epiglottis airspace width. SNA, SNB, and NSBA correlated with tongue width at the oropharynx. At tongue base, ANB and MP-H correlated with tongue width. SNB and NSBA were associated with deep tissue thickness at the oropharynx, while MP-H correlated with superficial tissue thickness at velum and oropharynx. Conclusions: Cephalometric parameters (SNA, SNB, ANB, NSBA, and MP-H) were correlated with ultrasonic parameters in the velum, oropharynx, tongue base, and epiglottis.

Color Duplex Ultrasonography for the Evaluation of Innominate, Subclavian, and Common Carotid Artery Stenosis.

This study aimed to validate the efficiency of Doppler ultrasonography for predicting the innominate, subclavian, and common carotid artery stenosis. This retrospective multicenter study between 2013 and 2022 enrolled 636 patients who underwent carotid Doppler ultrasonography and subsequent digital subtraction angiography. And 58 innominate artery stenosis, 147 common carotid artery stenosis, and 154 subclavian artery stenosis were included. The peak systolic velocity at innominate, subclavian, and common carotid artery, and velocity ratios of innominate artery to common carotid artery, innominate artery to subclavian artery, and common carotid artery to internal carotid artery were measured or calculated. The threshold values were determined using receiver operating characteristic analysis. The threshold values of innominate artery stenosis were peak systolic velocity >206 cm/s (sensitivity: 82.8%; specificity: 91.4%) to predict ≥50% stenosis and >285 cm/s (sensitivity: 89.2%; specificity: 94.9%) to predict ≥70% stenosis. The threshold values of common carotid artery stenosis were peak systolic velocity >175 cm/s (sensitivity: 78.2%; specificity: 91.9%) to predict ≥50% stenosis and >255 cm/s (sensitivity: 87.1%; specificity: 87.2%) to predict ≥70% stenosis. The threshold values of subclavian artery stenosis were peak systolic velocity >200 cm/s (sensitivity: 68.2%; specificity: 84.4%) to predict ≥50% stenosis and >305 cm/s (sensitivity: 57.9%; specificity: 91.4%) to predict ≥70% stenosis. Symptomatic patients with ultrasonic parameters of velocity at innominate artery ≥206 cm/s, velocity at common carotid artery ≥175 cm/s, or velocity at subclavian artery ≥200 cm/s need to be considered for further verification and whether revascularization is necessary.

Insight into Sonodynamic Activities of Gold Nanoparticles with Different Morphologies

AbstractThe sonodynamic activities of gold nanoparticles (GNPs) with different morphologies, gold nanospheres (GNSs), gold nanoflowers (GNFs) and gold nanorods (GNRs), were explored by multi‐spectroscopic methods, in which the lesion degree of human serum albumin (HSA) was used as assessment index. The results revealed that three GNPs all had certain sonosensitivity but varying from different morphologies. It was also found that GNPs concentration and ultrasonic parameters were all critical influencing factors of sonodynamic injury HSA. Investigating the physical damage mechanism, the results indicated that the secondary and tertiary structure of HSA were compromised by ultrasound (US) combined with GNPs, so that the conformation of HSA was altered and the function was variously disturbed due to GNPs different morphologies. Studying the chemical damage mechanism, the results discovered that the yield of singlet oxygen (1O2) produced by GNPs with various morphologies combined with US was significant difference. Therefore, comprehensively analyzing the research results under different factors, the order of sonodynamic activities of GNPs was GNSs≈GNFs>GNRs. These findings may provide reference for the application of GNPs as sonosensitizers in sonodynamic therapy.

A novel approach for state-of-charge estimation of lithium-ion batteries by quasi-static component generation of ultrasonic waves

Lithium-ion batteries content complex internal components, such as porous media and electrolytes, which result in strong scattering and high attenuation of ultrasonic waves in these batteries. The low attenuative feature of the quasi-static components (QSCs) of ultrasonic waves offers great potential for nondestructive assessment of highly attenuating and porous materials. This paper presents an innovative approach for estimating the state-of-charge (SOC) of lithium-ion batteries using QSC of ultrasonic waves. Experimental results demonstrate a clear and repeatable linear relationship between the amplitudes of the generated QSC and the SOC of lithium-ion batteries. In addition, the relationships between different SOCs of the battery and the conventional linear ultrasonic parameters, second harmonic generation (SHG), and the QSC were compared to verify the improved sensitivity of the proposed approach. Notably, compared to linear ultrasonic features and the SHG, the generated QSC shows much higher sensitivity to the variations of SOC. We employ the phase-reversal method to further enhance the signal-to-noise ratio of measured QSC signals. The experimental results demonstrate that the proposed method exhibits a heightened sensitivity to changes in the SOC of batteries, resulting in significantly enhanced detection accuracy and resolution. This method effectively addresses the deficiencies observed in the current detection methods such as limited accuracy and sluggish response times. This method provides a new solution to overcome this challenge. Meanwhile, it also confirms that nonlinear ultrasound promises an alternative method for SOC assessment, providing a foundation for efficient and safe battery management practices.

Advanced Excitation Symmetry Analysis Method (ESAM) for improved automated ultrasonic testing of polished materials

One of the strategic plans of the international NDT community is to define standards for developing advanced and digitalized non-destructive testing for automated set-up in mass production [1,2]. Excitation Symmetry Analysis Method (ESAM) are new coded signal processing tools exploring symmetry properties [3]. ESAM method aims to extract the nonlinearity from an ultrasound output by studying the property of symmetry of the transfer function. More precisely, the extraction of nonlinearity is done using basis function associated to a group which is associated to an a priori transfer function. As soon as the linear tomography uses the invariant properties of amplitude dependence, nonlinear tomography should exploit the invariance properties (or symmetry properties) of the complex system. Consequently, the invariance of the stationary properties of a complex medium would be supposed to be associated to a signature of the degradation, that will be extracted with advanced signal processing tools. The idea remains the same: studying the symmetry and more precisely the time reversal one and the inversion. A signal processing is used to measure discrepancies in the autocorrelation function (output signal called chirp coda) for two inputs: a signal and its inversion (pulse inversion). The experiments were done on different sample with and without cracks. It has been shown that when the nonlinearities are extracted from the chirp coda amplitude are non- negligible in crack area and nonlinearities are out of phase. Then, mixing symmetries like time reversal and pulse inversion enable the detection of defect that are difficult to detect with conventional ultrasound method. Indeed, for such crack a destructive mechanical analysis called Jomini is done where the material is polished and examined with microscope. The sensitivity improvement of chirp-coded signal processing has been validated in various domains. Coded excitation techniques, used in communication systems such as radar and sonar provide improved SNR without increasing the amplitude of excitation. The typical test equipment consists of a preamplifier Juvitek TRA-02 (0.02 - 5 MHz) connected to a computer, an amplifier ENI model A150 (55 dB at 0.3-35 MHz), a shear wave transducer Technisonic (2.25 MHz), and a longitudinal wave transducer Panametrics V155 (5 MHz). The experimental device was tested with the V3 calibration block, improved, and specially scaled in order to access to a wide range of multivalued parameters: mechanical properties, ultrasonic parameters (celerity and attenuation) and local geometric data.

Extraction of high activity bacterial urease and its application to biomineralization of soil

Biomineralization based on bacterial enzyme induced carbonate precipitation (BEICP) process is a promising alternative to cement-based ground treatment technology. The bacterial urease used in BEICP process is usually ultrasonic extracted from urease-producing bacteria. To efficiently extract urease with relatively higher activity from bacterial cells, the ultrasonic extraction parameters of urease were optimized in this study. Next, a series of bacterial urease extraction tests and sand column treatment tests were conducted to investigate the effects of vibration amplitude, upper temperature limit, and cooling method on the urease extraction process and biomineralization of sand. The results show that the upper temperature limit is an important factor affecting the extraction efficiency and the activity of the extracted urease solution, and the optimum upper temperature limit is 50 °C. The results indicate that increasing vibration amplitude could improve the extraction efficiency, but it hardly affects the urease activity (UA) under the optimal temperature. Continuous cooling could effectively simplify the operation and further improve the efficiency of urease extraction. Under the same urease activity of biotreatment solution, there is no marked difference in calcium carbonate content (CCC) and unconfined compressive strength of biomineralized sand columns prepared by urease solution extracted with different vibration amplitudes and upper temperature limits. The results of this study could provide a reference for application of BEICP technology of urease extraction to large-scale soil treatment.

Orthogonal experimental study of ultrasound-assisted fused deposition molding

To improve the quality of fused deposition molding (FDM), we introduced ultrasonic vibration into the molding process to enhance the strength of the tensile samples. We used the response surface method to optimize the FDM molding process. We carried out orthogonal experiments to investigate the effects of ultrasonic power and process parameters (extrusion temperature, hotbed temperature, and delamination thickness) on the mechanical properties of fused deposition acrylonitrile butadiene styrene products. We obtained the quadratic regression equations and response surfaces of the data through analysis of variance and significance analysis by software. Last, we received the optimum combination of process parameters for tensile strength as extrusion temperature 233.85 °C, hotbed temperature 93.38 °C, delamination thickness 0.1 mm, and ultrasonic power 43.09 W.

Data-driven online prediction of remaining fatigue life of a steel plate based on nonlinear ultrasonic monitoring

Online monitoring fatigue damage and remaining fatigue life (RFL) prediction of engineering structures are essential to ensure safety and reliability. A data-driven online prediction method based on nonlinear ultrasonic monitoring was developed to predict the RFL of the structures in real-time. Nonlinear ultrasonic parameters were obtained to monitoring the fatigue degradation. A Bayesian framework was employed to continuously compute and update the RFL distributions of the structures. Nonlinear ultrasonic experiments were performed on the fatigue damaged Q460 steel to validate the developed prediction methodology. The result indicates that the developed method has high prediction accuracy and can provide effective information for subsequent decision-making.

Pump and probe wave mixing for imaging nonlinear features embedded into a massive concrete block

Abstract Nonlinear ultrasonic parameters are known to be highly sensitive to the presence of damage in materials, and numerous methods have already been reported. This study proposes a way to image a nonlinear defect embedded into a nonlinear medium. The nonlinear defect is mimicked by a Berea sandstone sphere (high nonlinearity). It is placed into a large concrete block (average nonlinearity) during casting. The proposed pump and probe propagating wave interaction method allows imaging the presence of the highly nonlinear region. The image contrast is magnified by a factor 8 in the defective zone. The results are validated using a model and the individual mechanical properties of both concrete and Berea Sandstone. These findings open perspectives for application to civil engineering concrete structures such as the assessment of durability distresses involving internal swelling.

Study on Ultrasonic Characteristics and Prediction of Rock with Different Pore Sizes

The internal defects of rocks are the main cause of instability and failure in underground engineering. Therefore, using ultrasonic monitoring technology to study the defect characteristics of rocks containing voids is of great significance. The research results indicate that with the increase in the pore size, the longitudinal wave velocity and first wave amplitude of rocks containing voids decrease, the attenuation coefficient increases, and the difference in ultrasonic parameters between rocks containing voids and intact rocks increases, resulting in a significant decrease in the rock integrity. The propagation of ultrasonic waves in porous rocks can be divided into three stages, where obvious ultrasonic reflection, diffraction, and scattering occur. The attenuation of sound pressure is significant, and the ultrasonic sound pressure is negatively linearly correlated with the pore size. Based on the amplitude, velocity, and pressure of ultrasonic waves, an ANN-based method for predicting the pore size of rocks is proposed, which inverts and predicts the pore size of rock masses with high prediction accuracy.

Experimental study of ultrasonic wave propagation in a long waveguide sensor for fluid-level sensing

This work reports an ultrasonic long waveguide sensor for measuring the fluid level utilizing longitudinal L(0,1), torsional T(0,1), and flexural F(1,1) wave modes. These wave modes were transmitted and received simultaneously using stainless-steel wire. A long waveguide (12 m) covers a broader region of interest and is suitable in the process industry's hostile environment applications, "fluid levels and temperature measurements." In this work, we used fluids "diesel, water, and glycerin" for measuring fluid levels based on the sensor's reflection factors from time domain and frequency domain signals. We examined the impact of wave modes' attenuation effects for long waveguide sensor design while changing the waveguide lengths. Initially, we obtained the L(0,1) and T(0,1) modes reflections from the 12.6 m waveguide length when one end of the long waveguide was fixed with a shear transducer at 45° orientation. Subsequently, we want to study and identify all wave modes'' (especially F mode) travel distances. Hence, we would like to investigate the guided wave propagation characteristics (attenuation, ultrasonic velocity, and frequency of all wave modes) in the long waveguide while cutting systematically at intervals of 1 meter, starting from its original length of the waveguide 12.6 meters by analyzing the A-scan signals of various lengths of a single waveguide. This simple and cost-effective technique can monitor the high fluid depths and temperature in power plants, oil, and petrochemical industries while designing a long waveguide sensor with appropriate ultrasonic parameters.

Combined Color-Doppler Flow and Angio Planewave UltraSensitive™ Imaging for Analysis of Hemodynamic Characteristics of Normal Upper Limb Arteries

BackgroundTo evaluate the hemodynamic characteristics of normal upper extremity arteries from the brachial artery to the fingertip arterioles.MethodsWe analyzed the characteristics and changes in the regularities of ultrasonic parameters in the upper extremity arteries of 104 healthy volunteers using color Doppler flow imaging and Angio Planewave UltraSensitive™ imaging. The measured ultrasonic parameters included the vessel diameter, blood-flow spectrum waveform, peak systolic velocity, end-diastolic velocity, resistance index, pulsatility index, ratio of PSV to EDV, blood-flow volume, along with systolic acceleration of each BA, radial artery, superficial palmar arch artery, palmar proper digital artery, and third-grade artery arch of the fingernail bed.ResultsFrom BA to FN3AA, the diameter, PSV, RI, S/D, VFlow, and slope of the artery significantly decreased (P < 0.001), and size of the parameters significantly correlated with the anatomic position of the arteries. The blood-flow spectrum gradually changed from various waveforms to fixed monophasic waves. There was a linear relationship between the distribution of monophasic waveforms and arterial groups (R = -0.453; P < 0.001). When the blood-flow spectrum of BA and RA showed a monophasic waveform, their branch arteries showed the same. The waveforms of PPDA and FN3AA were also monophasic.ConclusionRegular changes in the blood-flow spectrum waveform and hemodynamic parameters are related to the anatomic position of the upper limb arteries. CDFI combined with Angio PLUS accurately and systematically evaluates the hemodynamic characteristics of the upper extremity arteries.

Surface Topography in Cutting-Speed-Direction Ultrasonic-Assisted Turning.

Ultrasonic vibration has been employed to assist in turning, introducing intermittent machining to reduce average cutting force, minimize tool wear, and enhance machining efficiency, thereby improving surface roughness. However, achieving intermittent cutting necessitates specific conditions, with a cutting speed or feed rate falling below the critical speed associated with the ultrasonic vibration parameters. This study presents a theoretical model for surface formation in cutting-speed-direction ultrasonic-assisted turning (CUAT), covering both continuous and intermittent machining regimes. Experimental validation was conducted on C45 carbon steel and 201 stainless steel to demonstrate the applicability of the theoretical model across different materials. Digital microscope analysis revealed 3D topography consistency with the theoretical formula. Surface roughness evaluations were performed for both CUAT and CT (conventional turning) methods. The results indicated a significant reduction in roughness Ra for C45 steel samples machined with CUAT, up to 80% compared to CT at a cutting speed of 20 m/min, while only exhibiting slight fluctuations when turning 201 stainless steel. Detailed analysis and explanation of these phenomena are presented herein.

Variation of Ultrasonic Velocity and a Few Acoustic Parameters as a Function Frequency in Some Commonly Used Edible Oils

In the present investigation an attempt is made to find out whether ultrasonic velocity and acoustic parameters vary as a function of frequency by using the ultrasonic technique. Ultrasonic velocities of commercially available edible oils were various frequencies by using Ultrasonic Multi-frequency Interferometer at room temperature. The density of the oils was determined by using a specific Gravity bottle of 10ml capacity at 30±0.1ºC. The present study gives information about the ultrasonic velocity changes as a function of frequency and the data of Ultrasonic Velocity and density obtained will be highly useful in estimating various acoustic parameters such as Acoustic impedance (Z), Bulk Modulus (K), and Adiabatic Compressibility (βad). Acoustic parameters and their variation in the systems of oils studied. The variation of ultrasonic velocity is critically discussed as a function of frequency and the data presented in the present work will be highly useful in identifying the adulteration in oils.

Clinical value of neutrophil to lymphocyte ratio and ultrasonic parameters in the diagnosis of bladder outlet obstruction in benign prostatic hyperplasia

AimThis study aimed to investigate the clinical significance of neutrophil-to-lymphocyte ratio and ultrasonic parameters in diagnosing bladder outlet obstruction in patients with benign prostatic hyperplasia. MaterialBetween September 2022 and January 2024, a total of 106 patients with benign prostatic hyperplasia were collected from Hongqi Hospital affiliated to Mudanjiang Medical University followed by urodynamic testing. The patients were categorized into three groups based on the International Prostate Symptom Score: mild (45 cases), moderate (36 cases), and severe (25 cases). Thirty-five healthy men were recruited at the hospital as a control group. All patients had blood tests and ultrasound scans. ResultsNeutrophil-to-lymphocyte ratio, detrusor wall thickness, detrusor muscle elastic modulus, internal gland elastic modulus, intravesical prostatic protrusion, and post-voiding residual volume were significantly correlated with the bladder outlet obstruction stage and showed good diagnostic efficiency (all P<0.05. There was no statistically significant difference observed in the external gland elastic modulus between the experimental group and the control group (P>0.05). ConclusionsThe neutrophil-to-lymphocyte ratio, detrusor wall thickness, elastic modulus of the detrusor and glandular gland may hold clinical significance for diagnosing bladder outlet obstruction resulting from benign prostatic hyperplasia. Level of evidence3.

Comparative study of linear and nonlinear ultrasound applied to the detection of hydrogen damage in 7N01 aluminum alloy

7N01 aluminum alloy samples with different hydrogen damage degrees were prepared by electrochemical hydrogen charging technology. 7N01 aluminum alloy samples with different degrees of hydrogen damage were characterized by metallographic observation, hardness test and XRD test. The results show that the hydrogen content increases with the increase of hydrogen charging time. The surface of aluminum alloy is exfoliated and pits appear. The more severe the hydrogen damage, the greater the depth of pits. The microhardness of the 7N01 aluminum alloy decreases after hydrogen damage, which only occurs near the surface. After electrochemical hydrogen charging, AlH3 appears in the structure of 7N01 aluminum alloy, which is the result of increased hydrogen concentration. The ultrasonic echo signals of hydrogen damaged samples were obtained by a high frequency longitudinal probe ultrasonic detection device, and the results of linear and nonlinear ultrasonic detection were compared. Traditional linear ultrasonic detection parameters such as sound velocity and attenuation coefficient do not change significantly in the early stage of hydrogen damage, but increase significantly in the late stage of hydrogen damage. Due to the change of microstructure, the nonlinear coefficient increases approximately linearly in the early stage of hydrogen damage and decreases in the late stage of hydrogen damage. This study demonstrates the potential for combining linear and nonlinear ultrasonic measurements in hydrogen environment to more comprehensively study hydrogen damage.

Enhancing hydrochar production and mitigating heavy metal risks in sewage sludge: The role of ultrasonic pretreatment in hydrothermal carbonization

Hydrothermal carbonization (HTC) is a potentially valuable technology for sewage sludge treatment and resource utilization. This study proposes a combined process of ultrasonic pretreatment and HTC to improve the yield and properties of hydrochar derived from sewage sludge (SS). SS was ultrasonically pretreated at different sound energy densities (0.6 – 1.4 W/mL) and pretreatment times (5 – 30 min), and then HTC conducted for 4 h in an autoclave. Ultrasonic pretreatment markedly enhanced the apparent structure and particle size of the feedstock, thereby improving the hydrothermal reactivity of SS. After ultrasonic pretreatment at 1.4 W/mL for 15 min, the yield of hydrochar derived from SS was 11.25% higher than that obtained after direct HTC. The hydrochar yield was also correlated with the ultrasonic pretreatment parameters. Ultrasonic pretreatment increased the specific surface area and number of oxygen-containing functional groups of the hydrochar and increased the energy density and energy yield by at most 7.63% and 9.56%, respectively. The impact of ultrasonic pretreatment on the heavy-metal pollution risk of hydrochar was evaluated in terms of the geological acumination index. Pretreatment with appropriate ultrasonic parameters decreased the pollution risks of Zn, Cu, Cr, and Pb. This study provides a valuable perspective on combined feedstock pretreatment and HTC, increasing the product value of HTC of sewage sludge.

Diaphragm ultrasound in patients with prolonged weaning from mechanical ventilation.

Several publications have examined diaphragmatic ultrasound using two-dimensional (2D) parameters in the context of weaning from mechanical ventilation (MV) and extubation. However, the studied cohorts had rather short duration of ventilation. Examinations on patients with prolonged weaning after long-term ventilation were missing. It was the aim of this study to assess of the diaphragm and peripheral musculature of patients undergoing prolonged weaning creating a chronological sequence of ultrasonic parameters during the course of weaning. This study was carried out as a monocentric, prospective observational cross-sectional study. Patients in prolonged weaning who were transferred to a specialized weaning unit were eligible for inclusion if they were ventilated invasively by means of an endotracheal tube or tracheal cannula and if their expected treatment period was at least 5 days. Diaphragmatic function and one representative peripheral muscle were examined in 50 patients between March 2020 and April 2021. The 2D sonographic parameters of diaphragm and diaphragmatic function consisted of diaphragmatic thickness (Tdi) at the end of inspiration and expiration, the fractional thickening (FT) and the diaphragmatic excursion. Additionally, the M. quadriceps femoris was sonographically assessed at two locations. The difference of measurements between the first and the last measuring timepoint were examined using the Wilcoxon signed-rank test. For a longer chronological sequence, the Friedman's rank sum test with subsequent Wilcoxon-Nemenyi-McDonald-Thompson test for multiple comparisons was carried out. Fifty patients with prolonged weaning were included. The median duration of MV before transfer to the weaning unit was 11.5 [interquartile range (IQR) 10] days. Forty-one patients could be assessed over the full course of weaning, with 38 successfully weaned. Within these 41 patients, the sonographic parameters of the diaphragm slightly increased over the course of weaning indicating an increase in thickness and mobility. Especially parameters which represented an active movement reached statistical significance, i.e., inspiratory Tdi when assessed under spontaneous breathing [begin 3.41 (0.99) vs. end 3.43 (1.31) mm; P=0.01] and diaphragmatic excursion [begin 0.7 (0.8) vs. end 0.9 (0.6) cm; P=0.01]. The presence of positive end-expiratory pressure (PEEP) and pressure support did not influence the sonographic parameters significantly. The M. quadriceps femoris, in contrast, decreased slightly but constantly over the time [lower third: begin 1.36 (0.48) vs. end 1.28 (0.36) cm; P=0.054]. The present study is the first one to longitudinally analyse diaphragmatic ultrasound in patients with prolonged weaning. Sonographic assessment showed that Tdi and excursion increased over the course of prolonged weaning, while the diameter of a representative peripheral muscle decreased. However, the changes are rather small, and data show a wide dispersion. To allow a potential, standardized use of diaphragm ultrasound for diagnostic decision support in prolonged weaning, further studies in this specific patient group are required.