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Ensuring the vibration reliability of rotary machines is based on the reliable mathematical model of rotor movement. Considering the critical factors leading to a stability loss is an important problem in up-to-date machinery. However, the presence of fractional-order hydrodynamic features of gap seals and the effect of anomalous energy dissipation lead to a need to clarify existing rotordynamic models by considering the fractional-order terms. Therefore, this article deals with the comprehensive modeling approach to study forced oscillations of a single-mass rotor and check its dynamic stability considering the fractional-order origin of the damping force. Moreover, the impact of fractional order on the damping factor and dynamic stability of whirl movement considering the circulation force in gap seals, is still not fully explored. This problem adds particular importance to the presented research. As a result, a single-mass flexible rotor model was extended by considering the fractional-order damping force. Moreover, based on the discovered asymptotic property of the Mittag-Leffler function, the impact of fractional order on the amplitude-frequency response was also determined. Finally, boundaries for dynamic stability loss were identified considering the fractional-order damping force. Overall, the study allowed the development and substantiation of a more generalized scientific and methodological approach to ensuring the vibration reliability of rotary machines. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study on the effectiveness of spirometry and forced oscillation technique in reducing thoracic compliance. Topics mentioned include the measurement of impedance to air flow due to airway resistance and respiratory system compliance, some limitations associated with spirometry, and the influence of chest restriction on total lung capacity.

BACKGROUND: A 20% reduction in the FEV1 is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV1 is effort dependent, and some patients are not able to perform acceptable and repeatable forced expiration maneuvers. The goal of the present study was to investigate the diagnostic value of airway resistance measurement by forced oscillation technique (FOT), body plethysmography, and interrupter technique compared with the traditionally accepted standard FEV1 measurement in evaluating the responsiveness to methacholine during MCT. METHODS: We included in the study adult subjects referred for MCT because of asthma-like symptoms and with normal baseline spirometry. We modified routine MCT protocol by adding the assessment of airway resistance to the measurement of FEV1 at each step of MCT. RESULTS: We observed, in the subjects with airway hyper-responsiveness versus those with normal airway responsiveness, a significantly greater percentage change in median (interquartile range) FOT resistance at 10 Hz (25.9% [13.7%-35.4%] vs 16% [15.7%-27.2%]), plethysmographic resistance (70.2% [39.5%-116.3%] vs 37.1% [23.9%-81.9%]), and mean 6 SD conductance (241.3 6 15.4% vs 229.6 6 15.9%); and a significantly greater change in mean 6 SD FOT reactance at 10 Hz (-0.41 6 0.48 cm H2O/L/s vs -0.09 6 0.32 cm H2O/L/s) and at 15 Hz (-0.29 6 0.2 cm H2O/L/s vs -0.1 6 0.19 cm H2O/L/s). We also recorded significant differences in airway resistance parameters (FOT resistance at 10 Hz, FOT reactance at 15 Hz, plethysmographic airway resistance, and conductance indices as well as interrupter resistance) in FEV1 non-responders at the onset of respiratory symptoms during MCT compared with baseline. CONCLUSIONS: Measurements of airway resistance could possibly be used as an alternative method to spirometry in airway challenge. Significant changes in airway mechanics during MCT are detectable by airway resistance measurement in FEV1 non-responders with methacholine-induced asthma-like symptoms. (ClinicalTrials.gov registration NCT02343419.) [ABSTRACT FROM AUTHOR]

Copyright of Archivos de Bronconeumología (English Edition) is the property of Sociedad Espanola de Neumologia y Cirugia Toracica (SEPAR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: With increased survival rates and the consequent emergence of an adult population with cystic fibrosis (CF), developing novel tools for periodic evaluations of these patients has become a new challenge. Thus, we sought to determine the contribution of lung-volume quantification using multidetector computed tomography (CT) in adults with CF and to investigate the association between structural changes and functional abnormalities. METHODS: This was a cross-sectional study in which 21 adults with CF and 22 control subjects underwent lung-volume quantification using multidetector CT. Voxel densities were divided into 4 bands: -1,000 to -900 Hounsfield units (HU) (hyperaerated region), -900 to -500 HU (normally aerated region), -500 to - 100 HU (poorly aerated region), and -100 to 100 HU (non-aerated region). In addition, all participants performed pulmonary function tests including spirometry, body plethysmography, diffusion capacity for carbon monoxide, and the forced oscillation technique. RESULTS: Adults with CF had more non-aerated regions and poorly aerated regions with lung-volume quantification using multidetector CT than controls. Despite these abnormalities, total lung volume measured by lung-volume quantification using multidetector CT did not differ between subjects and controls. Total lung capacity (TLC) measured by body plethysmography correlated with both total lung volume (rs = 0.71, P < .001) and total air volume (rs = 0.71, P < .001) as measured with lungvolume quantification using multidetector CT. While the hyperaerated regions correlated with the functional markers of gas retention in the lungs (increased residual volume (RV) and RV/TLC ratio), the poorly aerated regions correlated with the resistive parameters measured by the forced oscillation technique (increased intercept resistance and mean resistance). We also observed a correlation between normally aerated regions and highest pulmonary diffusion values (rs = 0.68, P < .001). CONCLUSIONS: In adults with CF, lung-volume quantification using multidetector CT can destimate the lung volumes of compartments with different densities and determine the aerated and non-aerated contents of the lungs; furthermore, lung-volume quantification using multidetector CT is clearly related to pulmonary function parameters. [ABSTRACT FROM AUTHOR]

Forced oscillation technique (FOT) emerged as a non-invasive, computationally efficient, fast and reliable method used in clinical practice for lung evaluation by means of fractional order impedance. Only recently, FOT has been employed to assess respiratory properties at low frequencies. When measuring at low frequencies interference between the imposed pressure oscillations and the breathing signal of the subject occurs. To deal with these challenges filtering techniques have been proposed to avoid biased correlates in the impedance, but none proved to successfully separate this disturbance signal. Hence, in this paper we are investigating the usefulness of empirical mode decomposition techniques to eliminate the bias introduced by the breathing signal. Respiratory data from patients diagnosed with chronic obstructive pulmonary disease (COPD) were analyzed and the results indicate that the method can successfully fill the gap in reducing the bias in the estimated impedance. The preliminary results show that by using the decomposed signals to estimate the fractional order impedance a bias reduction of respiratory impedance evaluation can be achieved. [ABSTRACT FROM AUTHOR]

This paper presents an original protocol, method and deploying solution for monitoring respiratory impedance in mobile individuals. The purpose of the follow up study may be either short-term, or long-term. The proposed steps take into account effects of exercise, rest and sleep on the mechanical properties of the respiratory signals and their computed impedance as a function of time and frequency. The end-product is a wearable sensor, which may be linked in a network of sensors, cyber-physical systems containing mobile devices, central data logging archives and possible alarms to medical supervisor. The added value is that given a treatment profile, its efficacy can be measured by evaluation of respiratory impedance on a daily (regular) basis, without the necessity for the patient to come to healthcare units provided with lung function test facilities. The visit to specialist can be then decided based on the follow-up online by the responsible person and treatment adaptation can be performed. Reduction of visits is thus an important factor in reducing healthcare costs and improving patient wellbeing while delivering highly qualitative services. [ABSTRACT FROM AUTHOR]

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 cmH2O to a maximum pressure and subsequently decreased until oxygenation deteriorated or a CDP of 8 cmH2O 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] cmH2O (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. [ABSTRACT FROM AUTHOR]

The Forced Oscillation Technique (FOT) is a lung function modality based on the application of an external oscillatory signal in order to determine the mechanical response of the respiratory system. The method is in principal noninvasive and requires minimal patient cooperation, which makes it suitable for use in young paediatric patients. The FOT has been successfully applied in various paediatric respiratory disorders, such as asthma, cystic fibrosis, and chronic lung disease of prematurity, in order to assess airway obstruction, bronchodilator response, and airway responsiveness after bronchoprovocation challenge. This technique may be more sensitive than spirometry in identifying disturbances of peripheral airways and assessing the level of asthma control or the effectiveness of therapy at the long term. Further research is required to determine the exact role of the FOT in paediatric lung function testing and to incorporate the method in specific diagnostic and management algorithms. [ABSTRACT FROM AUTHOR]

Introduction: Combination inhaled corticosteroid/long-acting bronchodilator (ICS/LABA) therapy reduces the exacerbation rate and improves spirometry and quality of life in COPD. We hypothesized that ICS/LABA therapy also improves small airway function measured by FOT. Methods: 14 subjects with COPD were commenced on combination fluticasone propionate/salmeterol therapy for 3 months. At baseline, subjects completed the St George Respiratory Questionnaire (SGRQ) and underwent standard pulmonary function tests as well as forced oscillation technique (FOT) and single and multiple breath nitrogen washouts. All tests were repeated at the completion of 3 months of therapy. Results: Subjects were of mean (SD) age 65.9 years (8.4), BMI 30.0 (5.6), pack years 51.4 (21.1), post-bronchodilator FEV1% predicted 62.7 (20). At baseline, mean SGRQ total was 39.0 (17.7) and FRC% predicted 125.4 (31.3). From FOT, Rrs-total was 5.69 (1.29) cmH2O/L/ s, Xrs-total -3.48 (2.16) cmH2O/L/s, EFL Index 3.51 (2.45) cmH2O/L/s. After 3 months of therapy, there were significant improvements in SGRQ score (-13.81, p < 0.0001) despite no change in FEV1 (+40 mL, p = 0.14). From FOT, total resistance (-0.63 cmH2O/L/s, p = 0.0004), reactance (+1.2 cmH2O/L/s, p = 0.013), and expiratory flow limitation (-1.21 cmH2O/L/s, p = 0.02) also improved. There were no significant changes in ventilation heterogeneity indices. Conclusion: Combination therapy is associated with improvements in small airways function in COPD, despite an absence of change in FEV1. FOT may be a clinically useful marker of small airway function in COPD that is responsive to treatment. [ABSTRACT FROM AUTHOR]

Copyright of Archivos de Bronconeumología (English Edition) is the property of Sociedad Espanola de Neumologia y Cirugia Toracica (SEPAR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Asthma guidelines recommend inhaled corticosteroid (ICS) dose titration for patients on the basis of an assessment of current asthma control. However, the physiological determinants of asthma symptom control are poorly understood and spirometry is a poor predictor of symptomatic response. Objective: To determine the role of small airway measurements in predicting the symptom response following ICS dose titration. Methods: Adult asthmatic patients had the Asthma Control Questionnaire (ACQ) scores and lung function measured at baseline and after 8 weeks. Tests included spirometry, plethysmography, sputum cell count, exhaled nitric oxide, airway hyperresponsiveness to mannitol, respiratory system mechanics using the forced oscillation technique, and ventilation heterogeneity using the multiple breath nitrogen washout. The parameters ventilation heterogeneity in convection-dependent airways and ventilation heterogeneity in diffusion-dependent airways were derived as measures of ventilation heterogeneity in the small airways. The dose of ICS was doubled if the ACQ score was greater than or equal to 1.5 (uptitration) and quartered if the ACQ score was less than 1.5 (downtitration). The relationships between baseline physiological parameters and the change in the symptom-only 5-item ACQ (deltaACQ-5) were examined by using Spearman correlations, forward stepwise linear regressions, and receiver operator curve analyses. Results: ICS dose uptitration (n = 20) improved ACQ-5 scores (1.76 to 1.16; P = .04). Baseline fraction of exhaled nitric oxide (r = −0.55; P = .01) and ventilation heterogeneity in convection-dependent airways (r = −0.64; P = .002) correlated with deltaACQ-5, but ventilation heterogeneity in convection-dependent airways was the only independent predictor (r 2 = 0.34; P = 0.007). ICS dose downtitration (n = 41) worsened ACQ-5 scores (0.46 to 0.80; P < .001), with 29% of the patients having a deltaACQ-5 of greater than 0.5. Only baseline ventilation heterogeneity in diffusion-dependent airways correlated with deltaACQ-5 (r = 0.40; P = .009) and identified subjects with deltaACQ-5 of greater than 0.5 (receiver operator curve area under the curve = 0.78; P = .0003). Conclusions: Ventilation heterogeneity predicts symptomatic responses to ICS dose titration. Worse small airways function predicts symptomatic improvement to ICS dose uptitration and loss of symptom control during downtitration. [Copyright &y& Elsevier]

Summary: Background: In COPD, improvements in lung mechanics following bronchodilator, measured using the forced oscillation technique (FOT), are more sensitive than spirometry at detecting improvement in lung function following bronchodilator. The relationship between these improvements in lung mechanics and improvements in functional outcomes, such as exertional dyspnoea, following bronchodilator, in COPD is unknown. Methods: 17 COPD subjects were recruited into a double blind placebo controlled randomised cross over study. Dyspnoea was induced using a standardised six-minute walk test (6 MWT), and measured by borg score throughout the test. Measurement of respiratory system conductance (Grs), respiratory system reactance (Xrs), inspiratory capacity (IC) and spirometry were made at baseline and 1 h after a single dose of either 18 μg of tiotropium bromide plus 200 μg salbutamol, or placebo. Results: Subjects had a mean baseline FEV1 of 45.5 ± 11.0% predicted. The bronchodilator induced reduction in exertional dyspnoea correlated significantly with the increase in Grs (rs  = 0.59, p = 0.01) and approached significance with FEV1 (rs  = 0.45, p = 0.07) but not with FVC (rs  = 0.30, p = 0.24), Xrs (rs  = 0.19, p = 0.47) or IC (rs  = −0.08, p = 0.78). Increase in Grs was the best and sole predictor of reduction in exertional dyspnoea, explaining 41% of the variance. There was no additional contribution to the model from the increase in FEV1 or IC. Conclusion: Bronchodilator induced improvements in exertional dyspnoea in moderate to severe COPD are predicted by improvements in Grs, measured by FOT, independent of improvements in spirometry or hyperinflation. The findings suggest that FOT may be useful for measuring response to bronchodilator in COPD. [Copyright &y& Elsevier]

Summary: Forced expiratory airflows and volumes are often used to assess the airway obstruction in asthmatics. However, forced maneuvers may change bronchial tone and modify airway patency. The aim of this study was to determine whether the Forced Oscillation Technique (FOT), which does not require forced manoeuvres, may be useful to describe the changes in respiratory mechanics in progressive asthma. This study involved 25 healthy and 84 asthmatics, including patients with normal spirometric exam (NE), mild moderate and severe obstruction. Resistive data were interpreted using the respiratory system resistance extrapolated at 0Hz (R0), the mean respiratory resistance (Rm), and the resistance/frequency slope (S). Reactance data were interpreted by its mean values (Xm), the dynamic compliance (Crs,dyn), and resonant frequency (fr). Receiver operating characteristics curves were used to determine the sensitivity (Se) and specificity (Sp) of FOT parameters in identifying asthma. There were not statistically significant differences between the control and NE groups. Comparing the control and mild groups, significant increases of R0 (), Rm (), and S () were observed. In reactive parameters, a significant reduction in Crs,dyn () was observed, while Xm and fr presented significant increases ( and , respectively). Comparison between mild and moderate groups showed non-significant modifications in all of the parameters, except for Xm (). In the late stages (moderate to severe obstruction), all of the resistive parameters, as well as the reactive ones Xm () and Crs,dyn , presented statistically significant modifications. Among the studied parameters, the effects of airway obstruction in asthma seem to be well described by R0, Rm, S and Xm, which were in close agreement with physiological fundamentals. The best parameters for detecting asthma were R0 (, ), S (, ) and Xm (, ). In conclusion, the results of this study suggest that the FOT can be proposed as an alternative method for the assessment of the respiratory mechanics in asthmatic patients, representing a promising solution to the problem of effort dependence. [Copyright &y& Elsevier]

Summary: The Forced Oscillation Technique (FOT) is a method for non-invasively assessing respiratory mechanics during spontaneous breathing, demanding little cooperation. The aim of this study was to test the ability of FOT to describe the changes in respiratory mechanics in progressive COPD. The study was performed in a control group formed by 21 healthy subjects and 79 outpatients with COPD, which were classified by spirometry, according to the degree of airway obstruction, in mild, moderate and severe groups. Resistive impedance data were submitted to linear regression analysis over the 4–16Hz frequency range, which yielded the total respiratory system resistance extrapolated at 0Hz (R 0), the respiratory system conductance (G rs), mean respiratory resistance (R m), and the resistance/frequency slope (S). Reactance data were interpreted using the mean values (X m) over the 4–32Hz frequency range, the dynamic compliance (C rs,dyn), the dynamic elastance (E rs,dyn), and the resonant frequency (f r) data. Considering the control and mild groups, the increase of airway obstruction resulted in a significant increase of R 0 (), R m (), and a significant reduction in G rs (). Reactive parameters, C rs, dyn and E rs,dyn also presented significant modifications. The subsequent increase (mild to moderate) showed a significant raise of R 0 (), S (), and a reduction in G rs (), while significant increases in X rs (), and E rs,dyn (), and also a reduction in C rs, dyn () were also observed. In contrast to earlier stages, in the late stage of the airway obstruction increase (moderate to severe obstruction), resistive parameters did not present statistically significant modifications, while significant modifications were observed in X rs (), C rs, dyn () and E rs,dyn (). The results of this study demonstrated that the FOT is useful for detecting the respiratory mechanics modifications in COPD patients. The initial phases of airway obstruction in COPD can be described mainly by resistive parameters, while in more advanced phases, reactive parameters seem to be more useful. Since the FOT has the advantage of being a simple method, such a technique may give a significant clinical contribution, representing an alternative and/or complement to the evaluation of respiratory mechanics by means of forced expiration. [Copyright &y& Elsevier]

Summary: Due to its non-invasive character, the forced oscillation technique has gained importance in clinical research in infants and young children. Standardisation has enabled systematic and comparable measurements to be made in different laboratories throughout the world. The theoretical conditions are now fulfilled for use of these techniques in the clinical environment. This review discusses the principles, usefulness and pitfalls of various forced oscillation techniques in a research and clinical environment and the present and future clinical applications in children. It will focus particularly on the role of infant and preschool lung function as forced oscillation only requires minimal cooperation. [Copyright &y& Elsevier]

Summary: FOT may hold the promise of improving the diagnosis of airway obstruction, but may be even better in quantifying the magnitude of airway reversibility and hyper-reactivity, helping in the adjustment of therapy, and monitoring disease progression in young children. [Copyright &y& Elsevier]