title: Trendelenburg position does not increase cross-sectional area of the internal jugular vein predictably.
abstract: BACKGROUND
  The Trendelenburg position is used to distend the central veins, improving both the success and safety of vascular cannulation. The purpose of this study was to measure the cross-sectional area (CSA) of the internal jugular vein (IJV) in three different positions using surface ultrasonography.
  
  
  METHODS
  Fifty-one subjects were enrolled. A Sono Site Titan 180 or M-Turbo portable ultrasound machine with a 10.5-mHz broadband linear surface probe was used. We measured the CSA of the IJV (at end-expiration at the level of the cricoid cartilage) in three positions: 15° reverse Trendelenburg, supine, and 15° Trendelenburg.
  
  
  RESULTS
  The mean CSA at 15° reverse Trendelenburg was 0.83 cm2 (SD, 0.86), in the supine position it was 1.25 cm2 (SD, 0.98), and at -15° Trendelenburg it was 1.47 cm2 (SD, 1.03). Moving from reverse Trendelenburg to supine, the CSA increased by 50%. In contrast, lowering the head to a Trendelenburg position increased the mean CSA by only 17%. Surprisingly, Trendelenburg positioning reduced the CSA in nine of the 51 subjects.
  
  
  CONCLUSIONS
  Trendelenburg positioning augments the CSA only modestly, on average, compared with the supine position, and in some patients it reduces the CSA.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT01099254; URL: www.clinicaltrials.gov.
authors: Division of Pulmonary Diseases, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors: Boulos
authors: B
authors: Nassar
authors: Division of Pulmonary Diseases, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors: Gur Raj S
authors: GRS
authors: Deol
authors: Division of Pulmonary Diseases, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors: Andrew
authors: A
authors: Ashby
authors: Division of Pulmonary Diseases, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors: Nicole
authors: N
authors: Collett
authors: Division of Pulmonary Diseases, Critical Care, and Occupational Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA. Electronic address: Gregory-a-schmidt@uiowa.edu.
authors: Gregory A
authors: GA
authors: Schmidt
mesh_terms: D000328:Adult; D000368:Aged; D019412:Anatomy, Cross-Sectional / Q000379:methods*; D002405:Catheterization, Central Venous; D016638:Critical Illness; D005260:Female; D018475:Head-Down Tilt; D006801:Humans; D007362:Intensive Care Units; D007601:Jugular Veins / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D012984:Software; D016683:Supine Position; D014463:Ultrasonography