Abstract

Intra-breath (IB) FOT parameters (measured between the 0-flow points at end-expiration and end-inspiration) may better reflect deranged lung mechanics than whole-breath (WB). While PROs like spirometry, correlate weakly-moderately with WB FOT parameters, the correlation between PROs and IB parameters is unknown. We hypothesized PROs would correlate more strongly with IB than WB FOT parameters. 50 (M=F) COPD subjects (>10 pack-year smoking and either FEV1/FVC<0.7, MMEF<65%predicted or RV>130%predicted) had PROs (COPD Assessment Tests, mMRC), spirometry (Jaeger or Vmax22, Carefusion, Germany), and FOT (tremoFlo C-100, Thorasys, Canada) abstracted from charts. Pearson’s r was determined between both CAT and mMRC vs. FEV1 and WB Z5, R5, X5, AX as well as IB (inspiratory and expiratory) R5 (R5in/ex), X5 (X5in/ex) and AX (AXin/ex). Significance was p<0.05 after Bonferroni correction. Means±SD were for age 72±10, pack-years 43±18, FEV1 61±26% predicted, FEV1/FVC 51±17, CAT 16±7 and mMRC 2.34±1.27. Correlations are shown in Table 1.

CAT correlated more strongly with IB than WB FOT parameters for R5, and AX, and mMRC for R5 and X5. The reason for these stronger correlations is unclear. We speculate that dynamic changes of lung mechanics are important drivers of respiratory symptoms. Validation of these findings in larger cohorts would support the usefulness of IB FOT parameters for the evaluation of COPD.