title: Changes in the superior vena cava area during inspiration and expiration in relation to emphysema.
abstract: BACKGROUND
  In patients with emphysema, increased intrathoracic pressure is closely related to hyperinflation and leads to hemodynamic impairments. Both intrathoracic pressure and hemodynamics such as venous return are affected by the respiratory phase. Therefore, respiratory variations in hemodynamics may be associated with the extent of emphysema that causes increased intrathoracic pressure. The current study was designed to evaluate the relationship between respiratory phasic variations in the area of the superior vena cava (SVC) and the extent of emphysema.
  
  
  METHODS
  We measured the SVC area and calculated the ratio of the SVC area in inspiratory and expiratory scans (i/e-SVC ratio) in 101 patients with emphysema who underwent both inspiratory and expiratory CT. The correlation of the i/e-SVC ratio with the extent of emphysema (%LAA) obtained by CT images was evaluated. Multiple linear regression analysis using i/e-SVC ratio as the dependent variable was performed.
  
  
  RESULTS
  The i/e-SVC ratio had a significant positive correlation with%LAA (ρ = 0.582, p <0.0001). The i/e-SVC ratio was significantly higher in patients with severe emphysema (0.86 ± 0.13) than in patients with mild-moderate emphysema (0.69 ± 0.13) (p <0.0001). Multiple linear regression analysis showed that%LAA was the only independent predictors of the i/e-SVC ratio (r(2) = 0.471, p = 0.0006).
  
  
  CONCLUSIONS
  Respiratory phasic variations in the SVC area are significantly correlated with the extent of emphysema.
authors.affiliation: 1Department of Radiology, St. Marianna University School of Medicine , Kawasaki , Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yamashiro
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Kotoku
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Matsushita
authors.forename: Atsuko
authors.initials: A
authors.lastname: Fujikawa
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Yagihashi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kurihara
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakajima
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014683:Vena Cava, Superior / Q000000981:diagnostic imaging / Q000503:physiopathology*
keywords: Computed tomography; expiration; hemodynamics; hyperinflation; intrathoracic pressure; venous return