title: Transjugular intrahepatic portosystemic shunts (TIPS): effects of respiratory state and patient position on the measurement of Doppler velocities.
abstract: OBJECTIVE
  The purpose of this prospective study was to examine the effects of patient position and respiratory state on the measurements of Doppler velocities in transjugular intrahepatic portosystemic shunts.
  
  
  METHODS
  Thirty-eight transjugular intrahepatic portosystemic shunts in 34 consecutive patients were studied using Doppler sonography. Peak velocities were measured in the mid shunt with the patient in three positions (supine, sitting upright, and left lateral decubitus) and two respiratory states (deep inspiration and quiet respiration). A mixed linear regression model was used to assess statistically significant differences among the six velocity measurements.
  
  
  RESULTS
  Peak velocities in the mid stent averaged 22 cm/sec greater in quiet respiration than in deep inspiration, which was a significant difference (p < 0.00001). Differences in velocities in the three patient positions were not significant (p = 0.53). Using 90-190 cm/sec as the normal range, the peak velocity shifted from normal to abnormal levels by changing respiratory state in 17 (45%) of 38 studies. Using 60 cm/sec as the lower normal limit, the peak velocity fell below the normal range with inspiration in 10 (26%) of 38 studies. In 12 (32%) of 38 studies, a decline in peak velocity exceeding 50 cm/sec could be induced by inspiration.
  
  
  CONCLUSIONS
  Peak systolic velocity in transjugular intrahepatic portosystemic shunts is substantially altered by the respiratory state of the patient at the time of the measurement, but not by the patient position. Respiratory state must be taken into account in the interpretation of peak velocity for shunt stenosis.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Kliewer
authors.forename: B S
authors.initials: BS
authors.lastname: Hertzberg
authors.forename: J P
authors.initials: JP
authors.lastname: Heneghan
authors.forename: P V
authors.initials: PV
authors.lastname: Suhocki
authors.forename: D H
authors.initials: DH
authors.lastname: Sheafor
authors.forename: P A
authors.initials: PA
authors.lastname: Gannon
authors.forename: E K
authors.initials: EK
authors.lastname: Paulson
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D005260:Female; D006503:Hepatic Veins / Q000000981:diagnostic imaging* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011169:Portal Vein / Q000000981:diagnostic imaging* / Q000502:physiology; D019168:Portasystemic Shunt, Transjugular Intrahepatic; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D012119:Respiration; D018608:Ultrasonography, Doppler