Document Detail

Changes in respiratory mechanics with increasing degrees of airway obstruction in COPD: detection by forced oscillation technique.
MedLine Citation:
PMID:  16115754     Owner:  NLM     Status:  MEDLINE    
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 4-16 Hz frequency range, which yielded the total respiratory system resistance extrapolated at 0 Hz (R0), the respiratory system conductance (Grs), mean respiratory resistance (Rm), and the resistance/frequency slope (S). Reactance data were interpreted using the mean values (Xm) over the 4-32 Hz frequency range, the dynamic compliance (Crs,dyn), the dynamic elastance (E(rs,dyn)), and the resonant frequency (fr) data. Considering the control and mild groups, the increase of airway obstruction resulted in a significant increase of R0 (P<0.008), Rm (P<0.001), and a significant reduction in Grs (P<0.002). Reactive parameters, Crs, dyn and Ers,dyn also presented significant modifications. The subsequent increase (mild to moderate) showed a significant raise of R(0) (P<0.007), S (P<0.001), and a reduction in Grs (P<0.015), while significant increases in Xrs (P<0.001), and Ers,dyn (P<0.02), and also a reduction in Crs, dyn (P<0.02) 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 Xrs (P<0.02), Crs, dyn (P<0.003) and Ers,dyn (P<0.003). 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.
Ana Maria G T Di Mango; Agnaldo J Lopes; José M Jansen; Pedro L Melo
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-08-22
Journal Detail:
Title:  Respiratory medicine     Volume:  100     ISSN:  0954-6111     ISO Abbreviation:  Respir Med     Publication Date:  2006 Mar 
Date Detail:
Created Date:  2006-02-15     Completed Date:  2006-08-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8908438     Medline TA:  Respir Med     Country:  England    
Other Details:
Languages:  eng     Pagination:  399-410     Citation Subset:  IM    
Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering, Brazil.
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MeSH Terms
Case-Control Studies
Forced Expiratory Volume
Middle Aged
Oscillometry / standards*
Pulmonary Disease, Chronic Obstructive / physiopathology*
Respiratory Mechanics / physiology*
Sensitivity and Specificity
Vital Capacity

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