Collapsibility of lung volume by paired inspiratory and expiratory CT scans: correlations with lung function and mean lung density.
OBJECTIVE
To evaluate the relationship between measurements of lung volume (LV) on inspiratory/expiratory computed tomography (CT) scans, pulmonary function tests (PFT), and CT measurements of emphysema in individuals with chronic obstructive pulmonary disease.


METHODS
Forty-six smokers (20 females and 26 males; age range 46-81 years), enrolled in the Lung Tissue Research Consortium, underwent PFT and chest CT at full inspiration and expiration. Inspiratory and expiratory LV values were automatically measured by open-source software, and the expiratory/inspiratory (E/I) ratio of LV was calculated. Mean lung density (MLD) and low attenuation area percent (<-950 HU) were also measured. Correlations of LV measurements with lung function and other CT indices were evaluated by the Spearman rank correlation test.


RESULTS
LV E/I ratio significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV(1)%P, R = -0.56, P < .0001; FEV(1)/FVC, r = -0.59, P < .0001; RV/TLC, r = 0.57, P < .0001, respectively). A higher correlation coefficient was observed between expiratory LV and expiratory MLD (r = -0.73, P < .0001) than between inspiratory LV and inspiratory MLD (r = -0.46, P < .01). LV E/I ratio showed a very strong correlation to MLD E/I ratio (r = 0.95, P < .0001).


CONCLUSIONS
LV E/I ratio can be considered to be equivalent to MLD E/I ratio and to reflect airflow limitation and air-trapping. Higher collapsibility of lung volume, observed by inspiratory/expiratory CT, indicates less severe conditions in chronic obstructive pulmonary disease.
Yamashiro
Tsuneo
T
Center for Pulmonary Functional Imaging, Brigham and Women's Hospital, Boston, MA, USA. clatsune@yahoo.co.jp
Matsuoka
Shin
S
Bartholmai
Brian J
BJ
San José Estépar
Raúl
R
Ross
James C
JC
Diaz
Alejandro
A
Murayama
Sadayuki
S
Silverman
Edwin K
EK
Hatabu
Hiroto
H
Washko
George R
GR
D000368:Aged; D000369:Aged, 80 and over; D003720:Densitometry / Q000379:methods*; D004646:Emphysema / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed / Q000379:methods*