Transjugular intrahepatic portosystemic shunts (TIPS): Effects of respiratory state and patient position on the measurement of Doppler velocities

OBJECTIVE. The purpose of this prospective study was to examine the effects of patient position and respiratory state on the measurements of Doppler v elocities in transjugular intrahepatic portosystemic shunts. SUBJECTS AND METHODS. Thirty-eight transjugular intrahepatic portosystemic shunts in 34 consecutive patients were studied using Doppler sonography. Pe ak velocities were measured in the mid shunt with the patient in three posi tions (supine, sitting upright, and left lateral decubitus) and two respira tory states (deep inspiration and quiet respiration). A mixed linear regres sion model was used to assess statistically significant differences among t he six velocity measurements. RESULTS. Peak velocities in the mid stent averaged 22 cm/sec greater in qui et respiration than in deep inspiration, which was a significant difference (p < 0.00001). Differences in velocities in the three patient positions we re 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 respirato ry state in 17 (45%) of 38 studies. Using 60 cm/sec as the lower normal lim it, the peak velocity fell below the normal range with inspiration in 10 (2 6%) of 38 studies. In 12 (32%) of 38 studies, a decline in peak velocity ex ceeding 50 cm/sec could be induced by inspiration. CONCLUSION. Peak systolic velocity in transjugular intrahepatic portosystem ic shunts is substantially altered by the respiratory state of the patient at the time of the measurement, but not by the patient position. Respirator y state must be taken into account in the interpretation of peak velocity f or shunt stenosis.