title: Measurement of Femoral Vein Diameter by Ultrasound to Estimate Central Venous Pressure.
abstract: BACKGROUND
  Central venous pressure (CVP) can be estimated by ultrasound of the inferior vena cava (IVC), but imaging the IVC is sometimes challenging. The femoral vein is easily imaged by ultrasound and might therefore provide an alternate target for estimating CVP.
  
  
  OBJECTIVE
  To assess femoral vein diameter (FVD) measured by ultrasound imaging for estimating CVP.
  
  
  METHODS
  We prospectively measured CVP and FVD in 97 patients. Receiver operating characteristic curves were used to assess the ability of FVD to predict specific CVP values: less than 10 mm Hg, less than 8 mm Hg (low CVP), and greater than 12 mm Hg (high CVP). Interobserver variability of FVD measurement was assessed in 20 patients.
  
  
  RESULTS
  There was moderate correlation between FVD and CVP (r = 0.66, P < 0.001). FVD less than or equal to 0.8 cm was the best predictor of CVP < 10 mm Hg, with an area under the curve (AUC) of 0.894 and a 95% confidence interval (CI) of 0.82 to 0.97. FVD less than or equal to 0.7 cm performed best for predicting low CVP (AUC = 0.97; 95% CI, 0.94-0.99) and FVD greater than or equal to 1.0 cm for high CVP (AUC = 0.80; 95% CI, 0.72-0.89). However, FVD greater than or equal to 1.2 cm had the greatest specificity (94%) for high CVP. Interobserver variability in FVD measurements was 8.3 ± 7.2%.
  
  
  CONCLUSIONS
  The results of this exploratory study suggest that the accuracy of FVD measured by ultrasound imaging for estimating CVP is comparable to that which has been reported for ultrasound measurement of IVC diameter. FVD may provide an alternative approach when the IVC is difficult to image. Additional studies on other cohorts of patients are warranted to validate our proposed FVD cutoff values for predicting low and high CVP.
authors.affiliation: Division of Pulmonary and Critical Care, Hennepin County Medical Center, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Cho
authors.affiliation: Division of Pulmonary and Critical Care, Hennepin County Medical Center, University of Minnesota, Minneapolis, Minnesota.
authors.forename: David R
authors.initials: DR
authors.lastname: Williams
authors.affiliation: Division of Pulmonary and Critical Care, Hennepin County Medical Center, University of Minnesota, Minneapolis, Minnesota.
authors.forename: James W
authors.initials: JW
authors.lastname: Leatherman
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D002406:Catheterization, Peripheral / Q000379:methods; D002496:Central Venous Pressure / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D005268:Femoral Vein / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging
keywords: central venous pressure; critical care; ultrasound