title: Ultrasound accurately reflects the jugular venous examination but underestimates central venous pressure.
abstract: BACKGROUND
  Bedside ultrasound examination could be used to assess jugular venous pressure (JVP), and thus central venous pressure (CVP), more reliably than clinical examination.
  
  
  METHODS
  The study was a prospective, blinded evaluation comparing physical examination of external jugular venous pressure (JVPEXT), internal jugular venous pressure (JVPINT), and ultrasound collapse pressure (UCP) with CVP measured using an indwelling catheter. We compared the examination of the external and internal JVP with each other and with the UCP and CVP. JVPEXT, JVPINT, UCP, and CVP were compared graphically using Bland-Altman plots, and correlation coefficients were calculated.
  
  
  RESULTS
  The correlation coefficients comparing CVP to UCP, JVPEXT, and JVPINT were 0.62, 0.57, and 0.50, respectively. When UCP was compared with JVPEXT and JVPINT, correlation coefficients were 0.91 and 0.81, respectively. Last, the correlation coefficient comparing JVPEXT and JVPINT was 0.98. The Bland-Altman graphical comparison of methods technique revealed that CVP was often underestimated by UCP, and clinical examination of JVPEXT and JVPINT. In contrast, there was no systematic bias between UCP and either JVPEXT or JVPINT, nor between JVPEXT and JVPINT.
  
  
  CONCLUSIONS
  Ultrasound examination is capable of measuring accurately the JVP as judged from the internal or external jugular vein. However, like the JVP, ultrasound typically underestimates CVP. A systematic bias between UCP and CVP suggests the presence of a variable degree of venous tone, possibly signaling contraction of jugular venous smooth muscle.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT01099241; URL: clinicaltrials.gov.
authors.affiliation: Department of Internal Medicine, University of Iowa, 200 Hawkins Dr, C33-GH, Iowa City, IA 52242, USA.
authors.forename: Gur Raj
authors.initials: GR
authors.lastname: Deol
authors.forename: Nicole
authors.initials: N
authors.lastname: Collett
authors.forename: Andrew
authors.initials: A
authors.lastname: Ashby
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Schmidt
mesh_terms: D002496:Central Venous Pressure; D016638:Critical Illness; D005260:Female; D006801:Humans; D007601:Jugular Veins / Q000000981:diagnostic imaging* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography