Oscillometry as a Diagnostic Tool for Small Airways Obstruction in Symptomatic At-risk Individuals with Normal Spirometry: Baseline Data from the IeCAN Study

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Introduction: Current GOLD guidelines define pre-COPD as symptomatic individuals with lung abnormalities despite normal spirometry, but no diagnostic test exists. We assessed if oscillometry could objectively detect small airway obstruction in at-risk, symptomatic individuals. Methods: Indian Early COPD Assessment Network (IeCAN) study is an, ongoing, multicentric, double-blind, double-dummy, randomized controlled trial evaluating inhaled Vilanterol+Fluticasone versus placebo in symptomatic patients (CAT score>10) with a smoking history of more than 10 pack-years or equivalent biomass fuel exposure in presence of normal spirometry, but with Ax>6 on oscillometry (Tremoflo C100R).After 12 weeks treatment we assessed change in CAT score, Ax & R5-20. Results: Out of the 183 patients screened, 95 were randomised into the study so far. We present the data of 59 patients, who had a mean age of 43.7 years, BMI of 25.6 kg/m², a mean smoking history of 14.4 pack-years, and 13 had biomass exposure of 17.2 years. The prebronchodilator mean FEV1 was 2.7L +/-0.5(90% predicted), FVC was 3.3 L+/-0.6(92.5% predicted) and FEV1/FVC of 78.4, while the mean FEF25-75 was 2.8L(68% predicted). Mean prebronchodilator oscillometry indices showed an Ax(cmH2O/L) of 18.6(8.8,19.8), R5-20(cmH2O) of 1.02 Pre, and X5(cmH2O) of -2.5(-2.4,-1.5). No correlation was found between CAT score &R5 or Ax values. Conclusion: Smokers and biomass smoke exposed subjects with significant respiratory symptoms and normal spirometry, show significantly abnormal Ax, R5-20 & X5 values highlighting the role of Oscillometry in the diagnosis of pre-COPD where small airways are affected.

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