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      International Journal of COPD (submit here)

      This international, peer-reviewed Open Access journal by Dove Medical Press focuses on pathophysiological processes underlying Chronic Obstructive Pulmonary Disease (COPD) interventions, patient focused education, and self-management protocols. Sign up for email alerts here.

      39,063 Monthly downloads/views I 2.893 Impact Factor I 5.2 CiteScore I 1.16 Source Normalized Impact per Paper (SNIP) I 0.804 Scimago Journal & Country Rank (SJR)

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      Impact of exacerbations on respiratory system impedance measured by a forced oscillation technique in COPD: a prospective observational study

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          Abstract

          Background

          Forced oscillation technique (FOT) has been reported to be useful in the evaluation and management of obstructive lung disease, including COPD. To date, no data are available concerning long-term changes in respiratory system impedance measured by FOT. Additionally, although exacerbations have been reported to be associated with excessive lung function decline in COPD, the impact of exacerbations on the results of FOT has not been demonstrated. The aim of this study was to investigate the longitudinal changes in respiratory system impedance and the influence of exacerbations thereon.

          Methods

          Between March 2011 and March 2012, outpatients who attended Kobe City Medical Center West Hospital with a diagnosis of COPD were assessed for eligibility. Baseline patient characteristics (age, sex, body mass index, smoking history, current smoking status, COPD stage), lung function (post-bronchodilator forced expiratory volume in 1 second [FEV 1]), blood tests (neutrophils and eosinophils), FOT, and COPD assessment test results were collected at enrollment. Lung function and FOT were examined every 6 months until March 2016. Annual changes in FEV 1 and FOT parameters were obtained from the slope of the linear regression curve. The patients were divided into 2 groups based on exacerbation history.

          Results

          Fifty-one of 58 patients with COPD were enrolled in this study. The median follow-up period was 57 (52–59) months. Twenty-five (49%) patients experienced exacerbations. A significant annual decline in FEV 1 and respiratory system impedance were shown. Additionally, annual changes in FEV 1, respiratory system resistance at 5 Hz, respiratory system reactance at 5 Hz, and resonant frequency were greater in patients with exacerbations than in those without exacerbations.

          Conclusion

          Exacerbations of COPD lead not only to a decline in lung function but also to an increase in respiratory system impedance.

          Most cited references15

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          The forced oscillation technique in clinical practice: methodology, recommendations and future developments.

          , K Desager, E Oostveen … (2003)
          The forced oscillation technique (FOT) is a noninvasive method with which to measure respiratory mechanics. FOT employs small-amplitude pressure oscillations superimposed on the normal breathing and therefore has the advantage over conventional lung function techniques that it does not require the performance of respiratory manoeuvres. The present European Respiratory Society Task Force Report describes the basic principle of the technique and gives guidelines for the application and interpretation of FOT as a routine lung function test in the clinical setting, for both adult and paediatric populations. FOT data, especially those measured at the lower frequencies, are sensitive to airway obstruction, but do not discriminate between obstructive and restrictive lung disorders. There is no consensus regarding the sensitivity of FOT for bronchodilation testing in adults. Values of respiratory resistance have proved sensitive to bronchodilation in children, although the reported cutoff levels remain to be confirmed in future studies. Forced oscillation technique is a reliable method in the assessment of bronchial hyperresponsiveness in adults and children. Moreover, in contrast with spirometry where a deep inspiration is needed, forced oscillation technique does not modify the airway smooth muscle tone. Forced oscillation technique has been shown to be as sensitive as spirometry in detecting impairments of lung function due to smoking or exposure to occupational hazards. Together with the minimal requirement for the subject's cooperation, this makes forced oscillation technique an ideal lung function test for epidemiological and field studies. Novel applications of forced oscillation technique in the clinical setting include the monitoring of respiratory mechanics during mechanical ventilation and sleep.
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            Detection of expiratory flow limitation in COPD using the forced oscillation technique.

            P Santus, A Pedotti, Peter Macklem … (2004)
            Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
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              Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

              Nickolaos Koulouris, A Pedotti, A Aliverti … (2007)
              The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative.
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                Author and article information

                Journal
                Journal ID (nlm-ta): Int J Chron Obstruct Pulmon Dis
                Journal ID (iso-abbrev): Int J Chron Obstruct Pulmon Dis
                Journal ID (publisher-id): International Journal of COPD
                Title: International Journal of Chronic Obstructive Pulmonary Disease
                Publisher: Dove Medical Press
                ISSN (Print): 1176-9106
                ISSN (Electronic): 1178-2005
                Publication date Collection: 2017
                Publication date (Electronic): 03 February 2017
                Volume: 12
                Pages: 509-516
                Affiliations
                Department of Respiratory Medicine, Kobe City Medical Center West Hospital, Kobe, Japan
                Author notes
                Correspondence: Takahiro Kamada, Department of Respiratory Medicine, Kobe City Medical Center West Hospital, 4, 2-chome, Ichibancho, Nagata-ku, Kobe 653-0013, Japan, Tel +81 78 576 5251, Fax +81 78 576 5358, Email takahiro00920619@ 123456gmail.com
                Article
                Publisher ID: copd-12-509
                DOI: 10.2147/COPD.S124828
                PMC ID: 5304968
                SO-VID: e9a31769-268d-4d76-bbbc-4a7ffd04c551
                Copyright © © 2017 Kamada et al. This work is published and licensed by Dove Medical Press Limited
                License:

                The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                History
                Categories
                Subject: Original Research

                ScienceOpen disciplines: Respiratory medicine
                Keywords: chronic obstructive pulmonary disease,forced oscillation technique,lung function tests,respiratory system,impedance,resistance
                Data availability:
                ScienceOpen disciplines: Respiratory medicine
                Keywords: chronic obstructive pulmonary disease, forced oscillation technique, lung function tests, respiratory system, impedance, resistance

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