Blog
About

3
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: not found

      Airway dynamics in COPD patients by within-breath impedance tracking: effects of continuous positive airway pressure

      Read this article at

      ScienceOpenPublisher
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Tracking of the within-breath changes of respiratory mechanics using the forced oscillation technique may provide outcomes that characterise the dynamic behaviour of the airways during normal breathing.

          We measured respiratory resistance ( R rs) and reactance ( X rs) at 8 Hz in 55 chronic obstructive pulmonary disease (COPD) patients and 20 healthy controls, and evaluated R rs and X rs as functions of gas flow ( V′) and volume ( V) during normal breathing cycles. In 12 COPD patients, additional measurements were made at continuous positive airway pressure (CPAP) levels of 4, 8, 14 and 20 hPa.

          The R rs and X rs versus V′ and V relationships displayed a variety of loop patterns, allowing characterisation of physiological and pathological processes. The main outcomes emerging from the within-breath analysis were the X rs versus V loop area (AXV) quantifying expiratory flow limitation, and the tidal change in X rs during inspiration (Δ X I) reflecting alteration in lung inhomogeneity in COPD. With increasing CPAP, AXV and Δ X I approached the normal ranges, although with a large variability between individuals, whereas mean R rs remained unchanged.

          Within-breath tracking of R rs and X rs allows an improved assessment of expiratory flow limitation and functional inhomogeneity in COPD; thereby it may help identify the physiological phenotypes of COPD and determine the optimal level of respiratory support.

          Related collections

          Most cited references 32

          • Record: found
          • Abstract: found
          • Article: not found

          Detection of expiratory flow limitation in COPD using the forced oscillation technique.

          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.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Comparison of inspiratory and expiratory resistance and reactance in patients with asthma and chronic obstructive pulmonary disease.

            The usual analysis of forced oscillometry measures respiratory resistance (Rrs) and reactance (Xrs) averaged over several tidal breaths (whole-breath analysis). Recent within-breath analyses have separated Rrs and Xrs into their mean inspiratory and mean expiratory components (inspiratory-expiratory breath analysis) but these have not been used to compare patients with asthma and those with chronic obstructive pulmonary disease (COPD). Large inspiratory-expiratory variations in Xrs at 5 Hz (DeltaX5) in an individual have been used as a surrogate marker of expiratory flow limitation. Whole-breath and inspiratory-expiratory impulse oscillometry was assessed in 34 patients with asthma (49 + or - 3 years; 15 male, forced expiratory volume in 1 s (FEV(1)) 69 + or - 4% predicted), 48 patients with COPD (64 + or - 2 years; 32 male, FEV(1) 59 + or - 3% predicted) and 18 normal subjects (37 + or - 2 years; 8 male). Whole-breath analysis failed to discriminate between patients with asthma and patients with COPD either for all patients or for patients with FEV(1) <60% predicted. Inspiratory-expiratory analysis in patients with FEV(1) <60% predicted showed that in the COPD group mean expiratory X5 (-0.44 + or - 0.04 kPa/l/s) was greater than inspiratory X5 (-0.23 + or - 0.02 kPa/l/s, p<0.001) whereas patients with asthma did not show such changes (-0.36 + or - 0.07 kPa/l/s vs -0.26 + or - 0.03 kPa/l/s, p=0.23). Even though DeltaX5 was larger in patients with COPD (0.21 + or - 0.03 kPa/l/s) than in patients with asthma (0.10 + or - 0.07 kPa/l/s), this was not significant (p=0.15). Whole-breath impulse oscillation system analysis failed to discriminate between patients with asthma and those with COPD. Inspiratory-expiratory X5 analysis differentiated patients with asthma from those with COPD presumably reflecting enhanced dynamic airway narrowing on expiration in COPD. Further studies are needed to confirm these differences and investigate their cause.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Respiratory system impedance with impulse oscillometry in healthy and COPD subjects: ECLIPSE baseline results.

              Current assessment of COPD relies extensively on the use of spirometry, an effort-dependent maneuver. Impulse oscillometry (IOS) is a non-volitional way to measure respiratory system mechanics, but its relationship to structural and functional measurements in large groups of patients with COPD is not clear. We evaluated the ability of IOS to detect and stage COPD severity in the prospective ECLIPSE cohort of COPD patients defined spirometrically, and contrasted with smoking and non-smoking healthy subjects. Additionally, we assessed whether IOS relates to extent of CT-defined emphysema. We measured lung impedance with IOS in healthy non-smokers (n = 233), healthy former smokers (n = 322) or patients with COPD (n = 2054) and related these parameters with spirometry and areas of low attenuation in lung CT. In healthy control subjects, IOS demonstrated good repeatability over 3 months. In the COPD group, respiratory system impedance was worse compared with controls as was frequency dependence of resistance, which related to GOLD stage. However, 29-86% of the COPD subjects had values that fell within the 90% confidence interval of several parameters of the healthy non-smokers. Although mean values for impedance parameters and CT indices worsened as GOLD severity increased, actual correlations between them were poor (r ≤ 0.16). IOS can be reliably used in large cohorts of subjects to assess respiratory system impedance. Cross-sectional data suggest that it may have limited usefulness in evaluating the degree of pathologic disease, whereas its role in assessing disease progression in COPD currently remains undefined. Copyright © 2011. Published by Elsevier Ltd.
                Bookmark

                Author and article information

                Journal
                European Respiratory Journal
                Eur Respir J
                European Respiratory Society (ERS)
                0903-1936
                1399-3003
                February 23 2017
                February 2017
                February 2017
                February 15 2017
                : 49
                : 2
                : 1601270
                Article
                10.1183/13993003.01270-2016
                © 2017

                Comments

                Comment on this article