Introduction: In cystic fibrosis lung disease starts in early infancy in peripheral small airways which progressively involves central larger airways. FEV1 is most used parameter for monitoring lung disease and index for newer molecular treatment effect. Forced oscillation technique (FOT) also called Oscillometry, is used to measure the mechanical properties of the respiratory system. This study was done to evaluate correlation between two methods

Methodology: This was a prospective observational study from a tertiary centre done from November 2020-December 2021. Children with cystic fibrosis and non-cystic fibrosis were enrolled and lung function test were done with spirometry and forced oscillation. Correlation was calculated  using Spearman?s correlation coefficient.

Results: 15 children with cystic fibrosis, 10 children with non-cystic fibrosis along with 10 normal children total of 35 children were enrolled. The Mean±SD age (years) in children with CF was 11.24 ± 4.163 while of non-Cystic fibrosis was 10.57 ± 1.83 and 10.07 ± 2.81 of normal children. The Mean±SD of FEV1%predicted (L) in CF group was 42.606±24.126 in non-CF 44.75±19.05 and 87.95±10.04 in normal children. The Mean±SD of resistance R 5Hz % predicted in CF patients was 161.342±74.140 while in non-CF group 177.64±103.66.

Conclusion: Across the all three group it was found that FEV1 and FVC, FEF25-75 correlate negatively with resistance and impedance with varied significance level while positive correlation with reactance.