Objective
To evaluate the relationship between the lung volume (LV) in inspiration and expiration,pulmonary function tests (PFT),and other CT measurements of emphysema index (EI) and mean lung density (MLD) in patients with chronic obstructive pulmonary disease (COPD).
Methods
Seventy-six patients with COPD were included.Three-dimension analysis was performed to obtain the following CT parameters on the inspiratory and expiratory phases: EI,MLD,LV.The ratios and differences of MLD and LV between the two phases were calculated (ΔMLD,ΔLV,MLDex/in,LVex/in).Not only the linear correlations between the lung volume parameters and PFT but also the correlations of lung volume parameters with the other CT parameters were tested by the Spearman rank correlation test and multivariant step wise regression.
Results
LVex/inhad negative correlations with forced expiratory volume in 1 second% predicted[FEV1%,(54.32±7.11) ]and the ratio of forced expiratory volume in 1 second to forced vital capacity[FEV1/FVC,(49.12±8.01) %] (r=-0.69,-0.56,P<0.01),but it had the positive correlation with the ratio of residual volume to total lung capacity[RV/TLC,(58.03±8.55) %,Spearman coefficients 0.66,P<0.01].LVex/in (0.67±0.12) was positively correlated with MLDex/in (0.89±0.04,r=0.88,P<0.01).The further multivariate step wise regression demonstrated that EI,LV and MLD could introduce a regression equation withR2=0.77 and 0.73,respectively (P<0.01).
Conclusions
There is an association between LVex/in and the parameters of routine PFT,which can reflect the collapsibility of lung.Moreover,LVex/incan be considered to be equivalent to MLDex/in.Taking into account the impact of scanning parameters on MLDex/in,LVex/inmay play a complementary role in the assessment of pulmonary function.
Key words:
Pulmonary disease,chronic obstructive; Respiratory function tests;
Objective
To investigate the correlation between the paired inspiratory and expiratory quantitative CT and pulmonary function tests (PFTs) in patients with chronic obstructive pulmonary disease (COPD).
Methods
A total of 84 patients with COPD were enrolled.For each patient,CT scan was performed in deep inspiration and expiration.Using automatic post-processing software,a three-dimension quantitative measurement was employed to assess the CT parameters of emphysema and air trapping.The correlation between CT and PFT was evaluated by the Spearman rank correlation test and multivariate linear regression analysis.
Results
The percent 1[Perc1,(-984.28±17.93) HU] and percent 15[Perc15,(-948.35±22.26) HU] from the CT parameters of emphysema were positively correlated with the forced expiratory volume in 1 second predicted (FEV 1%,48.69±23,47),the ratio of forced expiratory volume in 1 second over forced vital capacity[FEV1/FVC,(45.89±15.36) %,r=0.45—0.67,P<0.01],was negatively correlated with the ratio of residual volume to total lung capacity[RV/TLC,(61.32±14.48) %].The other CT parameters of emphysema index (EI) and the parameters of air trapping,the change in relative lung volume with attenuation values from-860 to-950 HU[RVC-860—-950,(17.66±22.36) %],the expiration to inspiration ratio of mean lung density (MLDex/in,0.93±0.06),the expiration to inspiration ratio of lung volume (LVex/in,0.71±0.14) had negative correlations with log FEV1%,FEV1/FVC (r=-0.48—-0.69,P<0.01) and positive correlations with RV/TLC (r=0.41—0.66,P<0.01).The further univariate linear regressions showed that EI,Perc1,Perc15,RVC-860—-950,MLDex/in,LVex/inwere correlated with the parameters of PFTs (Rsquare values of the regression equation,ranged from 0.27 to 0.66,P<0.01).After the pairwise combinations of the parameters of emphysema and air trapping,multivariate stepwise regressions showed betterRsquare values from 0.66 to 0.85.
Conclusions
CT parameters of emphysema and air trapping can reflect pulmonary function in COPD patients.The combinations of the two types of CT parameters are more correlated with the PFTs parameters.
Key words:
Lung diseases,obstructive; Respiratory function tests; Tomography,X-ray computed
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