A test cases library is created to provide a common foundation to test methods for locating the source of a poorly damped or forced oscillation by using wide-area measurements. The library is built ...on a simplified WECC 179-bus system and includes both poorly damped and forced oscillation cases. Three source locating methods were fully tested using the library, and two selected cases for each method are presented in this paper to demonstrate the advantages and the disadvantages of each method. This library would help validate, evaluate and improve methods locating the oscillation sources in power systems.
Rats are often used in ventilator-induced lung injury (VILI) models. However, strain-specific susceptibility for VILI has not been elucidated yet. The aim of this study was to demonstrate ...strain-specific differences in VILI in infant Sprague-Dawley and Wistar rats. VILI was compared in 2-wk-old pups after 8 h of protective or injurious ventilation. Pups were ventilated with tidal volumes (V
) of ∼7 mL/kg and positive end-expiratory pressures (PEEP) of 6 cmH
O (V
7 PEEP6) or with V
of ∼21 mL/kg and PEEP 2 cmH
O (V
21 PEEP2). Interleukin-6, macrophage inflammatory protein-2 (MIP-2), inflammatory cells, and albumin in bronchoalveolar lavage fluid (BALF); histology; and low-frequency forced oscillation technique (LFOT) and pressure-volume (PV) maneuvers were assessed. Alveolar macrophages, neutrophils, and MIP-2 derived from BALF revealed more pronounced VILI after V
21 PEEP2 in both strains. LFOT and PV analyses demonstrated rat strain-specific differences both at baseline and particularly in response to V
21 PEEP2 ventilation. Sprague-Dawley rats showed higher airway and tissue resistance and elastance values with no difference in hysteresivity between ventilation strategies. Wister rats challenged by V
21 PEEP2 experienced significantly more energy dissipation when compared with V
7 PEEP6 ventilation. In conclusion, both rat strains are useful for VILI models. The degree of VILI severity depends on ventilation strategy and selected strain. However, fundamental and time-dependent differences in respiratory system mechanics exist and reflect different lung tissue viscoelasticity. Hence, strain-specific characteristics of the respiratory system need to be considered when planning and interpreting VILI studies with infant rats.
The present study was aimed to compare the respiratory impedance of children residing in areas with different ambient air pollution (AAP).
A comparative cross-sectional pilot study was carried out in ...healthy school children of two cities in India i.e. Agra and Bhopal. Agra is one of the most polluted cities of India and AAP of Agra is much higher as compared to Bhopal, the reference city in the present study. The respiratory impedance was measured at 5, 11, and 19 Hz by forced oscillation technique (FOT). The anthropometric parameters, respiratory resistance at 5 Hz (R5), small airway resistance (R5-19), and reparatory reactance at 5 Hz (X5) of children from above two cities were compared by Student's t-test.
A total 114 children (57 boys) from Agra and 151 children (76 boys) from Bhopal aged 9–16 years were recruited. The children from Agra were younger (11.9 ± 1.9 yr vs. 13.1 ± 2.2 yr, p < 0.001) as compared to Bhopal, though their anthropometric parameters were comparable. The magnitude of R5 (5.53 ± 1.81 cmH20/L/s vs. 5.10 ± 1.77 cmH20/L/s, p = 0.05), X5 (−1.46 ± 0.65 cmH20/L/s vs. −1.17 ± 0.63 cmH20/L/s, p < 0.001), and R5-19 (0.79 ± 0.79 cmH20/L/s vs. 0.56 ± 0.78 cmH20/L/s, p = 0.023) in children of Agra were higher as compared to children of Bhopal. The differences in impedance were significantly higher between boys, but not between girls.
The present study demonstrates a higher magnitude of small airway dysfunction in children exposed to high AAP. A future study involving larger samples and longitudinal measurements of respiratory impedance will provide better insights.
•Respiratory impedance of children affected by long-term exposure to air pollution.•Particulate matter exposure associated with small airways dysfunction in children.•Boys as compared to girls are more susceptible to adverse effects of air pollution.•Small airways function assessment is valuable tool to evaluate air pollution.
Objective To characterize changes in lung mechanics and right ventricular output (RVO) during incremental/decremental continuous distending pressure (CDP) maneuvers in newborn infants receiving ...high-frequency oscillatory ventilation, with the aim of evaluating when open lung maneuvers are needed and whether they are beneficial. Study design Thirteen infants on high-frequency oscillatory ventilation were studied with a median (IQR) gestational age of 261 (253 -291 ) weeks and median (IQR) body weight of 810 (600-1020) g. CDP was increased stepwise from 8 cmH2 O to a maximum pressure and subsequently decreased until oxygenation deteriorated or a CDP of 8 cmH2 O was reached. The lowest CDP that maintained good oxygenation was considered the clinically optimal CDP. At each CDP, the following variables were evaluated: oxygenation, respiratory system reactance (Xrs), and RVO by Doppler echocardiography. Results At maximal CDP reached during the trial, 19 1 cmH2 O (mean SEM), oxygenation markedly improved, and Xrs and RVO decreased. During deflation, oxygenation remained stable over a wide range of CDP settings, Xrs returned to the baseline values, and RVO increased but the baseline values were not readily restored in all patients. Conclusion These results suggest that Xrs and RVO are more sensitive than oxygenation to overdistension and they may be useful in clinical practice to guide open lung maneuvers.
Signal disruptions in small animals during the realization of the Forced Oscillation Technique are a well-known cause of data loss as it leads to non-reliable estimations of the respiratory ...impedance. In this work, we assessed the effects of removing the disrupted epoch when a 3-seconds input signal composed of one and a half 2-seconds full cycle is used.
We tested our hypothesis in 25 SAMR1 mice under different levels of bronchoconstriction due to methacholine administration by iv bolus injections in different doses (15 animals) and by iv continuous infusion in different infusion rates (10 animals). Signal disruptions were computationally simulated as sharp drops in the pressure signal within a short timescale, and signal processing was performed using own developed algorithms.
We found that the model goodness of fit worsens when averaging techniques to estimate the input respiratory impedance are not used. However, no statistically significant differences were observed in the comparison between Constant Phase Model parameters of the full 3-s signal and the 2-s non disrupted epoch in all doses or infusion rates for both methacholine delivery strategies.
The proposed technique presents reliable outcomes that can reduce animal use in Forced Oscillation Technique realization.
To design machine learning classifiers to facilitate the clinical use and increase the accuracy of the forced oscillation technique (FOT) in the differential diagnosis of patients with asthma and ...restrictive respiratory diseases. FOT and spirometric exams were performed in 97 individuals, including controls (
n
= 20), asthmatic patients (
n
= 38), and restrictive (
n
= 39) patients. The first experiment of this study showed that the best FOT parameter was the resonance frequency, providing moderate accuracy (AUC = 0.87). In the second experiment, a neuro-fuzzy classifier and different supervised machine learning techniques were investigated, including
k
-nearest neighbors, random forests, AdaBoost with decision trees, and support vector machines with a radial basis kernel. All classifiers achieved high accuracy (AUC ≥ 0.9) in the differentiation between patient groups. In the third and fourth experiments, the use of different feature selection techniques allowed us to achieve high accuracy with only three FOT parameters. In addition, the neuro-fuzzy classifier also provided rules to explain the classification. Neuro-fuzzy and machine learning classifiers can aid in the differential diagnosis of patients with asthma and restrictive respiratory diseases. They can assist clinicians as a support system providing accurate diagnostic options.
•Particulate matter air pollution is common in military deployment environments of Iraq and Afghanistan.•Respiratory symptoms are frequently reported post-deployment, yet spirometry is frequently ...preserved.•Using the forced oscillation technique (FOT), 75% of veterans with preserved spirometry had distal airway dysfunction.•Veterans with distal airway dysfunction may represent at an at-risk population requiring closer surveillance.
To evaluate the utility of the forced oscillation technique (FOT) among military veterans with preserved spirometry and chronic unexplained respiratory symptoms.
178 veterans referred for evaluation of unexplained respiratory symptoms completed pulmonary function testing and FOT. Preserved spirometry was defined as FEV1/FVC, FEV1 and FVC ≥ 5th percentile. Frequency dependence of resistance (R4-R20) and reactance area (AX) were assessed via FOT, and R4-R20 ≥ 20% and AX ≥ 95th percentile were considered abnormal.
Spirometry was preserved in 71.3%, of whom 124 had acceptable FOT data. 93 of 124 (75.0%) veterans with preserved spirometry had one or more abnormal findings on FOT. Veterans with abnormal R4-R20 and/or AX had reduced FVC, FEV1, FEF25-75, and diffusing capacity (% predicted) in comparison to those with Normal FOT (p = 0.030 to p < 0.001).
In our referral sample, distal airway dysfunction in the presence of preserved spirometry appears common and may represent an at-risk group requiring closer surveillance.
At specific velocities, intense tonal sound can be radiated from the flow around cascaded flat plates. This sound arises from the coupled phenomena of vortex shedding and acoustic resonance. To ...suppress such noise, we actively control the vortex shedding and acoustic radiation by oscillating the edges of every second plate in the cascade. The objective of this investigation was to clarify the effects and mechanism of noise reduction under this control. To understand how the amplitude and frequency of the oscillations influence the controlled flow and acoustic fields around the flat-plate cascade, we conducted direct aeroacoustic simulations using the volume penalization method. The sound pressure level at the resonance frequency was decreased by oscillating the plates at a dimensionless amplitude of 0.15. The pressure reduction failed at oscillation frequencies close to the resonance frequency, because the acoustic resonance occurs at the oscillation frequency. In the audible range of oscillation frequencies (0–20 kHz), the audible overall sound pressure level was not able to be reduced. In contrast, at oscillation frequencies beyond the audible range, both the tonal sound pressure level at the resonance frequency and the audible overall level were decreased. Consequently, the noise radiated from a cascade of plates can be reduced by forced oscillations at a frequency above the audible range. Moreover, we offset the phase of the oscillations between two plates and observed the effect on the acoustic field. At a one-quarter phase offset, the sound pressure level at the oscillation frequency exhibited a vertical asymmetrical directivity.
To provide an evidence-based review of published data regarding normal range reference values and prediction equations for measurements of respiratory impedance using forced oscillation technique ...(FOT) and impulse oscillometry (IOs) in adults.
A non-language-restricted search was performed using forced oscillation technique and impulse oscillometry as primary terms. Original research studies reporting respiratory system impedance reference values or prediction equations based on cohorts of ≥100 healthy adults were included. Publications cited in identified studies were also considered for inclusion.
Of 882 publications identified, 34 studies were included: 14 studies of FOT, 19 studies of IOs, and one study of both techniques. Nineteen studies provided prediction equations. Most reports were from Europe (n = 20) and Asia (n = 12) and included relatively small cohorts (median = 264 subjects). Across publications, there was marked variability in performance and technique of impedance measurements. Height and sex emerged as major contributors to available prediction equations. The contribution of weight was more pronounced at the obese end of the weight spectrum. The contribution of age was less clear, and elderly were largely under-represented. Ethnicity likely plays a role, but was under-reported in currently available literature. Inclusion of current and former smokers in some studies further confound the results.
Currently available literature providing reference values and prediction equations for respiratory impedance measurements in adults is limited. Until larger-scale standardized studies are available, the choice of prediction equations should be based on datasets that best represent the target patient population and modality in use within each pulmonary physiology laboratory.
•Currently available reference values for adult impedance measures are limited.•Most current adult reference values are based on European Caucasians and Chinese.•There is marked variability between studies in measurement technique.•Forced oscillation and impulse oscillometry values may not be interchangeable.•Normal values obtained from large populations using standardized method are needed.
Within asthma, the small airways (≤2 mm in diameter) play an important role in pathophysiology. Using a combined clinical-computational approach, we sought to more precisely evaluate the contribution ...of the small airways to deep-breath induced airway dilation (in the absence of bronchial challenge), which may be impaired in severe asthma.
A patient-based computational model of the FOT was used to examine the sensitivity and specificity of FOT signals to small airways constriction at frequencies of 2 & 8 Hz. A clinical study of moderate to severe asthmatics (n = 24), and healthy volunteers (n = 10) was performed to evaluate correlations between baseline and post deep inspiration (following bronchodilator withhold and in the absence of prior bronchial challenge) forced oscillation technique (FOT) responses (at 2Hz and 8Hz) and asthma treatment intensity, spirometry, airway hyper-responsiveness and airway inflammation.
Computational modelling demonstrated that baseline resistance measures at 2Hz are both sensitive and specific to anatomical narrowing in the small airways. Furthermore, small airways resistance was significantly increased in asthmatics compared to health. Despite these differences, there were no noticeable differences between asthmatics and healthy volunteers in resistive measures following deep inspiration (DI) and DI responses of small airways were amplified in the presence of spirometry defined airflow limitation.
These results suggest that the small airways demonstrate increased resistance in moderate-to-severe asthma but dilate normally in response to deep inspirations in the absence of bronchial challenge. This suggests that effective targeting of the small airways is required to achieve functional improvements in moderate-severe asthmatic patients.
•The FOT can be used to study the small airways during tidal breathing at 2Hz•Computer models demonstrate that 2Hz FOT is sensitive to small airways disease.•Patients with severe asthma demonstrated small airways disease.•Severe asthmatics demonstrated normal responses in the small airways to deep inspiration.
PDF
