title: Within-breath analysis of respiratory mechanics in asthmatic patients by forced oscillation.
abstract: BACKGROUND
  The within-breath analysis of respiratory mechanics by the monofrequency Forced Oscillation Technique (mFOT) is of great interest in both physiopathology studies and the diagnosis of respiratory diseases. However, there are limited data on the use of this technique in the analysis of asthma. This study evaluates within-breath mechanics of asthmatic individuals and the contribution of the mFOT in the asthma diagnosis.
  
  
  METHODS
  Twenty-two healthy and twenty-two asthmatic subjects, including patients with mild (n=8), moderate (n=8), and severe (n=6) obstruction, were studied. Forced Oscillation Technique data were interpreted using the mean respiratory impedance (Zt), the impedance during inspiration (Zi), expiration (Ze), at the beginning of inspiration (Zii), and at expiration (Zie). The peak-to-peak impedance (Zpp) was also calculated by the subtraction of Zii from Zie. Receiver operating characteristic curves were used to determine the sensitivity (Se) and specificity (Sp) of m Forced Oscillation Technique parameters in identifying asthma.
  
  
  RESULTS
  Respiratory impedance values were significantly higher in asthmatics: Zt (p<0.001), Zi (p<0.001), Ze (p<0.001), Zii (p<0.001), Zie (p<0.001), and Zpp (p<0.003). The best parameters for detecting asthma were Zi, Zii, and Zie (Se=90.9%, Sp=90.9%), followed by Zt and Ze. These results are in close agreement with recently published theories and pathophysiological fundamentals.
  
  
  CONCLUSIONS
  mFOT permits a non-invasive and detailed analysis in different phases of the respiratory cycle, providing parameters that are adequate for the diagnosis of asthma with high accuracy. These results confirm the high clinical and scientific potential of this methodology in the evaluation of asthmatic patients.
authors.affiliation: Biomedical Instrumentation Laboratory, Institute of Biology, State University of Rio de Janeiro, Rio de Janeiro/RJ, Brazil.
authors.forename: Juliana
authors.initials: J
authors.lastname: Veiga
authors.forename: Agnaldo José
authors.initials: AJ
authors.lastname: Lopes
authors.forename: José Manoel
authors.initials: JM
authors.lastname: Jansen
authors.forename: Pedro Lopes de
authors.initials: PL
authors.lastname: Melo
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009991:Oscillometry / Q000379:methods*; D012372:ROC Curve; D015656:Respiratory Mechanics / Q000502:physiology*; D012680:Sensitivity and Specificity; D013147:Spirometry; D013997:Time Factors