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Table 3 Univariate correlations between ∆X5 (EFL index) and predictor variables

From: Predictors of expiratory flow limitation measured by forced oscillation technique in COPD

 

Rho

p value

Age (years)

0.087

0.4556

Pack-years

0.181

0.1217

mMRC scale

0.282

0.0161

CAT score

0.084

0.4712

Emphysema score

0.107

0.3609

FEV1 (% predicted)

-0.526

<0.0001

FVC (% predicted)

-0.365

0.0018

FEV1/FVC (%)

-0.518

<0.0001

IC (% predicted)

-0.212

0.0707

FEF 25-75% (% predicted)

-0.640

<0.0001

FRC (% predicted)

0.427

0.0003

RV (% predicted)

0.443

0.0002

TLC (% predicted)

0.245

0.0363

RV/TLC (% predicted)

0.448

0.0001

Whole-breath R5 (cmH2O/L/s)

0.669

<0.0001

∆R5 (cmH2O/L/s)

-0.211

0.0709

Whole-breath R20 (cmH2O/L/s)

0.528

<0.0001

∆R20 (cmH2O/L/s)

-0.007

0.9539

  1. Values are the Spearman rank correlation coefficient.
  2. Abbreviations: CAT COPD assessment test, Δ difference between inspiratory and expiratory phases, R5 and R20 respiratory system resistance at 5 Hz and 20 Hz, EFL expiratory flow limitation, FEF 25-75% forced expiratory flow between 25% and 75% of FVC, FEV1 forced expiratory volume in 1 second, FRC functional residual capacity, FVC forced vital capacity, IC inspiratory capacity, mMRC modified Medical Research Council, NA not applicable, RV residual volume, TLC total lung capacity.