title: Prospective analysis of cardiac collapsibility of inferior vena cava using ultrasonography.
abstract: OBJECTIVE
  The inferior vena cava (IVC) diameter and its respiratory change (respiratory variation) reportedly correlate well with the central venous pressure and response to fluid. However, changes in the IVC diameter are related to the cardiac rhythm (cardiac variation), which can be useful as an indicator for intravascular volume but can affect respiratory variation. We conducted a prospective analysis of this cardiac variation in adult emergency department patients.
  
  
  METHODS
  Ultrasonographic IVC images from 190 consecutive adult emergency department patients were collected prospectively. The IVC diameters 2 cm caudal from the middle hepatic vein were tracked automatically and measured. The IVC diameter changes were analyzed using a software program that tracks 2-dimensional motion in B-mode images. Cardiac and respiratory variations were calculated and analyzed.
  
  
  RESULTS
  The average IVC cardiac variation was 11.0% (95% confidence interval, 9.8%-12.3%) in these patients, which affects the respiratory variation resulting in 1.68-fold higher overestimation of respiratory variation. The coefficient of correlation between IVC cardiac variations and respiratory variations was 0.34 (P < .05).
  
  
  CONCLUSIONS
  The IVC cardiac variation affects our interpretation of ultrasonography IVC imaging. The IVC cardiac variation provides several advantages over other parameters of intravascular volume. Therefore, it can be a novel tool to assess the intravascular volume of the patients.
authors.affiliation: Emergency Medicine and Critical Care Medicine Department, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan. Electronic address: sonot-icu@h.u-tokyo.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sonoo
authors.affiliation: Hitachi General Hospital, Hitachi-shi, Ibaraki, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Ando
authors.affiliation: Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kon
authors.initials: K
authors.lastname: Sen
authors.affiliation: Emergency Medicine and Critical Care Medicine Department, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Maeda
authors.affiliation: Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Kobayashi
authors.affiliation: Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sakuma
authors.affiliation: Emergency Medicine and Critical Care Medicine Department, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kent
authors.initials: K
authors.lastname: Doi
authors.affiliation: Emergency Medicine and Critical Care Medicine Department, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Nakajima
authors.affiliation: Emergency Medicine and Critical Care Medicine Department, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yahagi
mesh_terms: D001810:Blood Volume / Q000502:physiology; D002496:Central Venous Pressure / Q000502:physiology*; D045853:Exhalation / Q000502:physiology; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014463:Ultrasonography; D014682:Vena Cava, Inferior / Q000033:anatomy & histology* / Q000000981:diagnostic imaging
keywords: Blood volume determination; Prospective study