• Gregory A Schmidt, Boulos Nassar, Gur Raj S Deol, Andrew Ashby, and Nicole Collett.
• Department of Internal Medicine, University of Iowa, Iowa City, IA 52246, USA.
• Chest. 2013 Jul 1;144(1):177-82.

BackgroundThe 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.MethodsFifty-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.ResultsThe 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.ConclusionsTrendelenburg positioning augments the CSA only modestly, on average, compared with the supine position, and in some patients it reduces the CSA.Trial RegistrationClinicalTrials.gov; No.: NCT01099254; URL: www.clinicaltrials.gov.

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