The site of airway obstruction among patients of emphysema: role of impulse oscillometry.

OBJECTIVES: To detect the site of airway obstruction in patients of emphysema by impulse oscillometry (IOS) and to compare its observatios with flow volume loop (FV loop) studies. METHODS: Twenty-five patients of emphysema were subjected to both impulse oscillometry (IOS) and conventional spirometry. The resulting impedance spectra by IOS and FV loop were utilized to identify the site of airway obstruction in each of the patients. Both methods applied were also compared for sensitivity to identify airway and specify the site of obstruction. RESULTS: Four patients were excluded from the final analysis as their impedance spectra showed significant upper airway influence, which would have made the localization of the site of airway obstruction by IOS invalid. Both IOS and FV loop could detect airway obstruction in all 21 patients. FV loop localized the site of obstruction as combined central and peripheral airways in 15 patients (71.4%) and as peripheral in 6 (28.6%).The IOS however, revealed the presence of the predominant site of obstruction peripheral in all the 21 patients, and both central and peripheral obstruction in 5 patients (23.8%). CONCLUSIONS: IOS had proven to be advantageous over FV loop studies as it could identify central and peripheral airway obstruction separately and established the predominant site of obstruction.

Clinical usefulness of checking wheezing and flow volume loop in methacholine bronchoprovocation test / 천식및알레르기

BACKGROUND: In methacholine bronchoprovocation test, lung function is traditionally measured by using forced vital capacity maneuver which depends on patient's effort. And insufficient breath may result in a false positive test. OBJECTIVE: To evaluate the additional indices of airflow obstruction in the interpretation of methacholine bronchoprovocation test. METHOD: FEV1/FVC, configuration index of flow-volume loop (Slope-Ratio), modified Borg dyspnea score, and wheezing in addition to FEV1 were measured before and after methacholine challenge. RESULTS: The changes of the measurements after methacholine challenge were significantly greater in patients with airway hyperresponsiveness (AHR). However, only 9 out of 29 (31.0%) patients with AHR developed all of indices and 6.9% did not show any evidence of obstruction except dyspnea. On the contrary, 40% of patients without AHR showed positive in two or more indices and 2 of them were hyperresponsive to histamine. Among patients with AHR, those without dyspnea and wheezing on challenge showed significantly lower baseline Borg score, FEV1, FEV1/FVC, and PC20, and were older than those with them (p<0.05). CONCLUSION: Methacholine-induced deltaFEV1 is related to, but not concordant with other indices of airflow obstruction. Development of dyspnea and wheezing depends on age, etc. For an accurate interpretation of methacholine bronchoprovocation test, it maybe necessary to consider these variables.