title: Within-breath respiratory impedance and airway obstruction in patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  Recent work has suggested that within-breath respiratory impedance measurements performed using the forced oscillation technique may help to noninvasively evaluate respiratory mechanics. We investigated the influence of airway obstruction on the within-breath forced oscillation technique in smokers and chronic obstructive pulmonary disease patients and evaluated the contribution of this analysis to the diagnosis of chronic obstructive pulmonary disease.
  
  
  METHODS
  Twenty healthy individuals and 20 smokers were assessed. The study also included 74 patients with stable chronic obstructive pulmonary disease. We evaluated the mean respiratory impedance (Zm) as well as values for the inspiration (Zi) and expiration cycles (Ze) at the beginning of inspiration (Zbi) and expiration (Zbe), respectively. The peak-to-peak impedance (Zpp=Zbe-Zbi) and the respiratory cycle dependence (ΔZrs=Ze-Zi) were also analyzed. The diagnostic utility was evaluated by investigating the sensitivity, the specificity and the area under the receiver operating characteristic curve. ClinicalTrials.gov: NCT01888705.
  
  
  RESULTS
  Airway obstruction increased the within-breath respiratory impedance parameters that were significantly correlated with the spirometric indices of airway obstruction (R=-0.65, p<0.0001). In contrast to the control subjects and the smokers, the chronic obstructive pulmonary disease patients presented significant expiratory-inspiratory differences (p<0.002). The adverse effects of moderate airway obstruction were detected based on the Zpp with an accuracy of 83%. Additionally, abnormal effects in severe and very severe patients were detected based on the Zm, Zi, Ze, Zbe, Zpp and ΔZrs with a high degree of accuracy (>90%).
  
  
  CONCLUSIONS
  We conclude the following: (1) chronic obstructive pulmonary disease introduces higher respiratory cycle dependence, (2) this increase is proportional to airway obstruction, and (3) the within-breath forced oscillation technique may provide novel parameters that facilitate the diagnosis of respiratory abnormalities in chronic obstructive pulmonary disease.
authors.affiliation: Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering, Universidade Estadual do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Karla Kristine Dames da
authors.initials: KK
authors.lastname: Silva
authors.affiliation: Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering, Universidade Estadual do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Alvaro Camilo Dias
authors.initials: AC
authors.lastname: Faria
authors.affiliation: Pulmonary Function Testing Laboratory, Discipline of Pneumology, Faculty of Medical Sciences, Universidade Estadual do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Agnaldo José
authors.initials: AJ
authors.lastname: Lopes
authors.affiliation: Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering and Laboratory of Clinical and Experimental Research in Vascular Biology, Biomedical Center, Universidade Estadual do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Pedro Lopes de
authors.initials: PL
authors.lastname: Melo
mesh_terms: D000368:Aged; D000403:Airway Resistance / Q000502:physiology*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D045853:Exhalation / Q000502:physiology*; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity