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Littérature scientifique sur le sujet « Forced oscillation (FO) »
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Articles de revues sur le sujet "Forced oscillation (FO)"
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Lorino, AM, F. Lofaso, F. Abi-Nader, I. Drogou, E. Dahan, F. Zerah, A. Harf et H. Lorino. « Nasal airflow resistance measurement : forced oscillation technique versus posterior rhinomanometry ». European Respiratory Journal 11, no 3 (1 mars 1998) : 720–25. http://dx.doi.org/10.1183/09031936.98.11030720.
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This study was designed to determine whether nasal airflow resistance (Rn) which is nonlinear during tidal breathing, can be assessed by the forced oscillation (FO) technique. Rn values obtained by the FO technique and extrapolated to 0 Hz (Rn,FO) were compared to those assessed by posterior rhinomanometry at maximal tidal inspiratory flow (Rn,m), at a 0.5 L x s(-1) flow (Rn,F), and at a 1 hPa transnasal pressure (Rn,P). All Rn estimates were derived from the same inspiratory and expiratory nasal flow and transnasal pressure signals obtained during tidal nasal breathing whilst a forced flow was applied at the nose via a rigid nasal mask in 23 healthy volunteers, of whom 14 had additional measurements after vasoconstrictor treatment. In the basal state, no significant difference, and significant correlations (p<0.0001) were found between Rn,FO and the other Rn estimates. Only the regression line of Rn,FO versus Rn,m was not significantly different from the identity line. After nasal decongestion, Rn,P became significantly higher than the other Rn estimates (p<0.005). The regression line of Rn,FO versus Rn,m remained nonsignificantly different from the identity line. Similar results were observed regarding the percentage values of the different Rn estimates after decongestant treatment. This study shows that, despite its nonlinearity, Rn can be assessed by the FO technique, and that Rn,FO and Rn,m could be indifferently used as physiological indices of nasal patency. As the FO technique is more difficult to implement than the conventional rhinomanometry, its interest in rhinology appears not to be obvious.
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Saadeh, C., M. D. Goldman, C. K. Saadeh et J. R. Lemert. « Objective evidence of omalizumab treatment assessed by Forced Oscillation (FO) ». Journal of Allergy and Clinical Immunology 119, no 1 (janvier 2007) : S5. http://dx.doi.org/10.1016/j.jaci.2006.11.037.
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Harf, A., M. Decramer, W. Zin, J. Milic-Emili et H. K. Chang. « Respiratory resistance in dogs by the single-breath and the forced oscillation methods ». Journal of Applied Physiology 59, no 1 (1 juillet 1985) : 262–65. http://dx.doi.org/10.1152/jappl.1985.59.1.262.
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Total respiratory resistance (Rrs) was measured in six anesthetized dogs with two different methods: the single-breath (SB) method, which provides the time constant of the system during a relaxed expiration and the forced oscillation (FO) method, which uses a pseudorandom noise signal applied at the airway opening. The comparison was made in three conditions: before muscle paralysis (A), after muscle paralysis (B), and after tracheal banding (C). In conditions A and B the two computed resistances correlated very well with each other (r = 0.98). No systematic difference between Rrs values obtained with the two methods was found. In condition C the respiratory resistance was clearly nonlinear from the flow-volume curves during SB and could be described with Rohrer's equation: Rrs = K1 X V + K2 X V2, where K1 and K2 are Kohrer's constant and V is flow. Rrs measured with FO was not frequency dependent during tracheal banding (C) and was virtually equivalent to K1. Since the FO method uses low flows as the input of the respiratory system and K1 could be ascribed to laminar flow, the numerical matching appears reasonable and tends to reinforce the validity of both methods of measurement. We conclude that, for the normal respiratory system, FO and SB methods are approximately equivalent. In the presence of a markedly alinear central airway resistance with normal lungs, the SB method appears to provide a more adequate description of the flow-resistive properties of the system.
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Tomioka, Shinichiro, Jason H. T. Bates et Charles G. Irvin. « Airway and tissue mechanics in a murine model of asthma : alveolar capsule vs. forced oscillations ». Journal of Applied Physiology 93, no 1 (1 juillet 2002) : 263–70. http://dx.doi.org/10.1152/japplphysiol.01129.2001.
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To better address the functional consequences of inflammation on bronchial responsiveness, we studied two groups of BALB/c mice: a nonimmunized control group ( n = 8) and a group immunized and challenged with inhaled ovalbumin ( n = 8). An alveolar capsule (AC) measured airway resistance (RawAC) and lung elastance (El). A forced oscillation (FO) technique independently estimated airway resistance (RawFO) and a parameter H ti related to tissue elastance. Ovalbumin-immunized and -challenged mice had increased numbers of eosinophils in bronchoalveolar lavage and increased responsiveness to methacholine (MCh). Corresponding parameters from the AC and FO techniques were correlated: RawAC vs. RawFO( r = 0.76) and El vs. H ti ( r = 0.88, P< 0.0001 in all cases). AC and FO techniques showed significant increases in tissue elastance in response to MCh but no significant increases in airway resistance. These results demonstrated that the AC and FO techniques yield essentially equivalent results in mice, even when the lung is inhomogeneous, and that the bronchoconstrictive responses to MCh and inflammation in mice are predominantly located in the lung periphery.
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Kumar, Lalit, Shehab Ahmed, Luigi Vanfretti et Nand Kishor. « Real-Time Testing of Synchrophasor-Based Wide-Area Monitoring System Applications Acknowledging the Potential Use of a Prototyping Software Toolchain ». International Transactions on Electrical Energy Systems 2022 (30 juillet 2022) : 1–13. http://dx.doi.org/10.1155/2022/6215040.
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This article presents a study on real-time testing of synchrophasor-based “wide-area monitoring system’s applications (WAMS application).” Considering the growing demand of real-time testing of “wide-area monitoring, protection, and control (WAMPAC)” applications, a systematic real-time testing methodology is formulated and delineated in diagrams. The diagrams propose several stages through which an application needs to be assessed (sequentially) for its acceptance prior to implementation into a production system. However, only one stage is demonstrated in this article which comprises the use of a prototyping software toolchain and whose potential is assessed as sufficient for preliminary real-time testing (PRTT) of WAMS applications. The software toolchain is composed of two components: the MATLAB software for application prototyping and other open-source software that allows ingesting prerecorded phasor measurement unit (PMU) signals. With this software toolchain, a PRTT study is presented for two WAMS applications: “testing of the PMU/phasor data concentrator (PDC)” and “testing of wide-area forced oscillation (FO) monitoring application.”
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Sotner, Roman, Jan Jerabek, Lukas Langhammer et Jan Dvorak. « Design and Analysis of CCII-Based Oscillator with Amplitude Stabilization Employing Optocouplers for Linear Voltage Control of the Output Frequency ». Electronics 7, no 9 (22 août 2018) : 157. http://dx.doi.org/10.3390/electronics7090157.
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This paper shows the topology design of a simple second-order oscillator based on two three-port current conveyors, two resistors, and two grounded capacitors, as well as its modification to a voltage-controlled oscillator (VCO). In comparison with many previous works, the following useful conceptual novelties and improvements were made in this study. Both resistors presented in the topology can be employed to tune of the oscillation frequency by the simultaneous driving of two optocouplers with resistive output stage. The current gain of the current conveyor ensures the control of the oscillation condition. The proposed solution offers advantages (in comparison with many standard so-called single-resistance-controllable types) of improved dependence of the frequency of oscillation (FO) on a driving force (extended tuning of the FO), constant ratio of amplitudes of generated waveforms when the FO is tuned, low complexity (taking into account auxiliary circuitry for optocouplers), and comfortable tuning of the FO by a single control voltage. The oscillator produces waveforms with tunable frequency having a constant 45-degree phase shift between them. The relative sensitivities of the proposed solution achieve typical values for these second-order systems (−0.5). Experimental verification confirmed the expected behavior in the operational band between 1 and 10 MHz tuned by a DC voltage from 1.7 to 5 V. This indicates a significant reduction of the driving force ratio (3:1 in our case) in comparison with standard tuning approaches required for a ratio of 10:1 for FO adjustment. Output amplitudes reached 100 and 150 mV in the observed tunability range with distortion ranging between 0.7 and 3.3%.
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Skloot, Gwen, Clyde Schechter, Alpa Desai et Alkis Togias. « Impaired response to deep inspiration in obesity ». Journal of Applied Physiology 111, no 3 (septembre 2011) : 726–34. http://dx.doi.org/10.1152/japplphysiol.01155.2010.
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Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.
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Kovacs, S. J., B. Barzilai et J. E. Perez. « Evaluation of diastolic function with Doppler echocardiography : the PDF formalism ». American Journal of Physiology-Heart and Circulatory Physiology 252, no 1 (1 janvier 1987) : H178—H187. http://dx.doi.org/10.1152/ajpheart.1987.252.1.h178.
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A new parametrized diastolic filling (PDF) formalism for evaluation of holodiastolic (left and right) ventricular function via Doppler echocardiography is presented. It is motivated by the empiric observation that during diastole the heart behaves as a suction pump whose dynamics, in certain respects, are those of a damped harmonic oscillator. An expression for elastic recoil (suction) initiated ventricular diastolic fluid inflow velocity v(t) is obtained by differentiation from the solution x(t) of the linear differential equation that describes the motion of a forced, damped harmonic oscillator. It is solved for “over-damped” motion, for zero initial velocity and initial displacement = xo cm. An explicit forcing term F(t) = Fosin(omega t) is included to account for late diastolic (atrial) filling. The quantitative parameters of the model include inertia (mass; m), viscosity (damping constant; c), source of stored energy for suction (spring constant; k), and its initial displacement xo, the amplitude and frequency of the (atrial) forcing term Fo, omega. The mathematical behavior of the solution v(t) and its dependence on the parameters xo, c, and k, which characterize the contour of the Doppler velocity profile (DVP), is discussed. When clinical examples of normal and abnormal transmitral DVPs are compared with v(t) calculated using the harmonic oscillator model, excellent agreement [DVP-v(t)]/v(t) approximately 0.05 is obtained throughout diastole. Thus the model allows accurate qualitative and quantitative characterization of global ventricular diastolic behavior by noninvasive means in a variety of normal and abnormal stiffness-compliance states. In addition, it may serve as a prototype for a class of mathematical models that can encompass the essential dynamic elements of ventricular diastolic function that couple to flow and further enhance the role of the heart as a suction pump.
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Zuhaib, Mohd, Mohd Rihan et Mohd Tayyab Saeed. « A novel method for locating the source of sustained oscillation in power system using synchrophasors data ». Protection and Control of Modern Power Systems 5, no 1 (décembre 2020). http://dx.doi.org/10.1186/s41601-020-00178-4.
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AbstractLarge interconnected power systems are usually subjected to natural oscillation (NO) and forced oscillation (FO). NO occurs due to system transient response and is characterized by several oscillation modes, while FO occurs due to external perturbations driving generation sources. Compared to NO, FO is considered a more severe threat to the safe and reliable operation of power systems. Therefore, it is important to locate the source of FO so corrective actions can be taken to ensure stable power system operation. In this paper, a novel approach based on two-step signal processing is proposed to characterize FO in terms of its frequency components, duration, nature, and the location of the source. Data recorded by the Phasor Measurement Units (PMUs) in a Wide Area Monitoring System (WAMS) is utilized for analysis. As PMU data usually contains white noise and appears as multi-frequency oscillatory signal, the first step is to de-noise the raw PMU data by decomposing it into a series of intrinsic mode functions (IMF) using Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) technique. The most appropriate IMF containing the vital information is selected using the correlation technique. The second step involves various signal processing and statistical analysis tools such as segmented Power Spectrum Density (PSD), excess kurtosis, cross PSD etc. to achieve the desired objectives. The analysis performed on the simulated two-area four-machine system, reduced WECC-179 bus 29 machine system, and the real-time power system PMU data set from ISO New England, demonstrates the accuracy of the proposed method. The proposed approach is independent of complex network topologies and their characteristics, and is also robust against measurement noise usually contained in PMU data.
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Tuza, Fábio Augusto d´Alegria, Paula Morisco de Sá, Hermano A. Castro, Agnaldo José Lopes et Pedro Lopes de Melo. « Combined forced oscillation and fractional-order modeling in patients with work-related asthma : a case–control study analyzing respiratory biomechanics and diagnostic accuracy ». BioMedical Engineering OnLine 19, no 1 (décembre 2020). http://dx.doi.org/10.1186/s12938-020-00836-6.
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Abstract Background Fractional-order (FrOr) models have a high potential to improve pulmonary science. These models could be useful for biomechanical studies and diagnostic purposes, offering accurate models with an improved ability to describe nature. This paper evaluates the performance of the Forced Oscillation (FO) associated with integer (InOr) and FrOr models in the analysis of respiratory alterations in work-related asthma (WRA). Methods Sixty-two individuals were evaluated: 31 healthy and 31 with WRA with mild obstruction. Patients were analyzed pre- and post-bronchodilation. The diagnostic accuracy was evaluated using the area under the receiver operating characteristic curve (AUC). To evaluate how well do the studied models correspond to observed data, we analyzed the mean square root of the sum (MSEt) and the relative distance (Rd) of the estimated model values to the measured resistance and reactance measured values. Results and discussion Initially, the use of InOr and FrOr models increased our understanding of the WRA physiopathology, showing increased peripheral resistance, damping, and hysteresivity. The FrOr model (AUC = 0.970) outperformed standard FO (AUC = 0.929), as well as InOr modeling (AUC = 0.838) in the diagnosis of respiratory changes, achieving high accuracy. FrOr improved the curve fitting (MSEt = 0.156 ± 0.340; Rd = 3.026 ± 1.072) in comparison with the InOr model (MSEt = 0.367 ± 0.991; Rd = 3.363 ± 1.098). Finally, we demonstrated that bronchodilator use increased dynamic compliance, as well as reduced damping and peripheral resistance. Conclusions Taken together, these results show clear evidence of the utility of FO associated with fractional-order modeling in patients with WRA, improving our knowledge of the biomechanical abnormalities and the diagnostic accuracy in this disease.