Simple forced oscillatory technique and spirometry in assessment of bronchial responsiveness in non-asthmatic and asthmatic subjects

Simple validity controlled forced oscillatory respiratory resistance (Rrsfo) at 8 Hz frequency was compared with flow-volume spirometry in detection of bronchial changes during induced bronchoconstriction. The methacholine provocation test was performed in subjects with mild asthma (n = 18) and in non-asthmatic subjects (n = 61) of which 44 were classified as responders (delta FEV1 > or = 15% in methacholine test). According to the index of maximal response/coefficient of variation for immediately repeated measurements (delta max/Coeffvar), Rrsfo was shown to be at least as sensitive indicator of bronchoconstriction as FEV1, and better than MMEF and FVC. The shape of the dose-response curves were similar for all parameters. In the non-asthmatic group, there were similar plateaux in Rrsfo, FEV1, and FVC at the same methacholine concentrations. In the asthmatic group, the provocative concentrations for Rrsfo and spirometric parameters correlated significantly (PC60-Rrsfo versus PC10-FEV1, P < 0.05; PC60-Rrsfo versus PC25-MMEF, P < 0.01). In the non-asthmatic responsive subjects, the correlations between PC60-Rrsfo and PC25-MMEF were significant (P < 0.05). Thus, Rrsfo at a fixed 8 Hz frequency and built-in validity control was shown to be at least as sensitive an indicator for changes in lung function in asthmatic and non-asthmatic responsive subjects as spirometry. Compared to spirometry, it may give additional information with fewer confounding factors during performance.