PURPOSE: To detect the site of airway obstruction among patients of asthma by impulse oscillometry (IOS) and to compare its observations with those of flow volume loop (FV Loop).
METHODS: Twenty-five patients of asthma were subjected to both impulse oscillometry (IOS) and conventional spirometry including flow volume loop. The resulting impedance spectra by IOS and findings of FV loop were utilized to identify the site of airway obstruction in each of patients. The both methods applied were also compared for sensitivity to identify obstruction and localise its site.
RESULTS: Two patients were excluded from the final analysis as their impedance spectra of IOS showed significant upper airway influence which would have made the localization of the site of airway obstruction invalid. Among remaining of 23 patients, IOS could detect airway obstruction in all of them (P<0.05), while FV loop revealed obstruction in 18 (78.2%) patients only. Furthermore FV loop localized the site of obstruction (combined central and peripheral airways) in 12 patients (52.2%); and the peripheral airway obstruction in 6 (26.1%) patients only. However, IOS revealed predominant central airway obstruction in 15 patients (65.5%) and predominant peripheral airway obstruction in 8 patients (34.5%).
CONCLUSION: The site of airway obstruction varied from central to peripheral (mainly central) in patients of asthma. IOS has proven to be an advantageous over FV loop studies as it could identify central and peripheral airway obstruction separately and established the predominant site of obstruction. Furthermore it could detect airway obstruction among those patients where FV loop studies were completely normal.
CLINICAL IMPLICATIONS: Both techniques IOS and FV Loop had their own characteristics and limitations. Both provided results by their own typical characteristics, information about mechanical behavior and properties of respiratory system. Impulse oscillometry was more sensitive in detecting airway obstruction and its site. In addition, IOS offers certain advantages over spirometry as it is effort independent, consumes less time and requires minimal patient's cooperation.
DISCLOSURE: Harmanjit Hira, No Financial Disclosure Information; No Product/Research Disclosure Information