Clinical Applications of Forced Oscillation Techniques FOT in patients with Bronchial Asthma

Abstract

Background:Forced oscillation technique (FOT) is a method to characterize the mechanical properties of the respiratory system over a wide range of frequencies. Its’ most important advantage is to require minimal cooperation from the subject. This study was performed to evaluate the usefulness of the FOT applications in patients with bronchial asthma by estimating the associations between asthma severity and FOT parameters, and the relationships between FOT and spirometry parameters.Methods:216 patients with asthma were enrolled in this study. Patients were classified into 3 different groups according to their symptoms and pulmonary functions. Respiratory impedance, resistance (at 5 Hz, 20 Hz, 35 Hz) and resonant frequency were measured by FOT. FEV1, FVC and MMEF were measured with conventional spirometry.Results:There were significant differences of resonant frequency, resistance at 5 Hz and 20 Hz, resistance difference at 5 Hz and 20 Hz according to asthma severity (p<0.05, respectively). Resonant frequency, resistance at 5 Hz, and impedance were significantly correlated with FEV1 (r = −0.55, −0.48, −0.49, p<0.05, respectively), and with MMEF in patients with normal pulmonary function (r = −0.37, −0.35, −0.34, p<0.05, respectively). Resistance at 5 Hz had similar reproducibility compared to FEV1 (resistance at 5 Hz, r = 0.78 vs FEV1, r = 0.79).Conclusion:FOT is a useful and alternative method to evaluate the clinical status of bronchial asthma. Further studies will be needed to clarify its value for a wide range of clinical applications.

Lung Function Measured by Impulse Oscillometry and Spirometry Following Eucapnic Voluntary Hyperventilation

“…Goldman et al (36) proposed that the integrated X over a range of low frequencies (5 Hz to F res ) provides meaningful evidence of airflow obstruction beyond the sensitivity of spirometry. Still others have shown that F res correlates best with baseline FEV 1 (r=-0.55) (28). Schmekel and Smith (31) found that the change in F res following EVH correctly diagnosed asthma with 89% sensitivity and 100% specificity.…”

“…Debate exists concerning which is more discriminating when detecting airway obstruction; however, it is widely accepted that IOS measurements are frequency-dependent with the pronounced changes occurring at lower frequencies (24,25,38,39). Some studies have shown that resistance at 5 Hz significantly correlates with baseline FEV 1 (26,28), postmethacholine challenge FEV 1 (25,27,32) or postbronchodilator FEV 1 values (24,33,38). Others have suggested that X at 5 Hz is most sensitive to changes in airway calibre.…”

“…Impulse oscillometry (IOS) has been used to measure short-term changes in bronchial tone in bronchodilator tests (24), and has been shown to correlate with FEV 1 (25)(26)(27)(28)(29)(30)(31)(32)(33) and airway resistance, which is determined by body plethysmography (34,35). IOS applies brief, random pressure pulses of 5 Hz to 35 Hz generated by a small loudspeaker mounted in series or parallel to a pneumotachometer.…”

Overall and peripheral lung function assessment by spirometry and forced oscillation technique in relation to asthma diagnosis and control

“…Forced oscillometry has been used to demonstrate airway obstruction and response to bronchodilation and challenge tests in asthma . There is evidence that this method is more sensitive than spirometry in asthma, but also that it has greater variability, especially with regard to reactance measures .…”

“…15 Forced oscillometry has been used to demonstrate airway obstruction and response to bronchodilation and challenge tests in asthma. [16][17][18][19] There is evidence that this method is more sensitive than spirometry in asthma, but also that it has greater variability, especially with regard to reactance measures. 20,21 Forced oscillometry can assess both overall and peripheral airway mechanics by utilizing low frequencies that travel all the way to the small airways and, thus, reflect the whole airway tree and high frequencies that travel only proximally, mainly reflecting central airways.…”