@article {Jarenb{\"a}ckP3963, author = {Linnea Jarenb{\"a}ck and G{\"o}ran Eriksson and Stefan Peterson and Leif Bjermer and Ellen Tufvesson}, title = {COPD severity related to extended measurements of lung volume, diffusion, and resistance}, volume = {44}, number = {Suppl 58}, elocation-id = {P3963}, year = {2014}, publisher = {European Respiratory Society}, abstract = {Background: We have previously shown that use of only FEV1 in COPD diagnosis and monitoring gives an incomplete characterization of the COPD patients. The aim of this post hoc study was to relate the severity of COPD to more advanced measures of lung function in COPD patients and healthy smokers by analyzing the data continuously.Method: Lung function of 65 COPD patients (GOLD 1-4) and 34 healthy smokers was tested using flow-volume spirometry, body plethysmography, single breath helium dilution with CO-diffusion and impulse oscillometry after 400μg salbutamol and 80 mg ipratropium. Relation between spirometric disease severity and different lung function measurements was descriptively analyzed with a flexible non-parametric smoothed fit (LOESS), linear regression (LR), as well as segmented linear regression (SLR). For SLR a cut point (CP) was determined and tested for relevance (p\>0.05 was classified as no CP).Results: Following lung function variables were better described by SLR (CP: Mean\%): FEV1/FVC (CP;72\%), TLC\%p (65\%), FRC\%p (65\%), RV\%p (64\%), Rtot\%p (82\%), DLCO/VA\%p (69\%), RVbb-co\%p (62\%), AX (64\%), X5 abs (63\%). LR was selected for the remaining variables (p\>0.05): FEV1\%p, Rex, Rin (p=0.054), DLCO\%p, RVco\%p, VA\%p, R20\%p, R5\%p, R5-20\%p.Conclusion: Different lung function variables measured with different techniques can give important information about the severity of COPD. Many volume-related outcomes showed a break-point around 65\% post-FEV1 and is probably related to increased air trapping. The finding is in the middle of GOLD 2 and might have implication for selection of outcomes depending of study population or vice versa.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/44/Suppl_58/P3963}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }