Original Article The Effects of Positioning on the Volume/Location of the Internal Jugular Vein Using 2-Dimensional Tracked Ultrasound Wanyu Wang, MD * ,# , Xinyang Liao, MD y,# , Elvis C.S. Chen, PhD z , John Moore, PhD z , John S.H. Baxter, PhD z , Terry M. Peters, PhD z , Daniel Bainbridge, MD, FRCPC x,1 * Department of Anesthesia, West China Hospital, Sichuan University, Chengdu, Sichuan, China y Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, China z Robarts Research Institute, Western University, London, Ontario, Canada x Department of Anesthesiology and Perioperative Medicine, Department of Medicine, Division of Critical Care, Western University, London, Ontario, Canada Objective: To investigate the effects of different positioning on the volume/location of the internal jugular vein (IJV) using 2-dimensional (2D) tracked ultrasound. Design: This was a prospective, observational study. Setting: Local research institute. Participants: Healthy volunteers. Interventions: Twenty healthy volunteers were scanned in the following 6 positions: (1) supine with head neutral, rotated 15 and 30 degrees to the left and (2) 5-, 10-, and 15-degree Trendelenburg position with head neutral. In each position the volunteer’s neck was scanned using a 2D ultrasound probe tracked with a magnetic tracker. These spatially tracked 2D images were collected and reconstructed into a 3D volume of the IJV and carotid artery. This 3D ultrasound volume then was segmented to obtain a 3D surface on which measurements and calculations were performed. Measurements and Main Results: The measurements included average cross-section area (CSA), CSA along the length of IJV, and average over- lap rate. CSA (mm 2 ) in the supine and 5-, 10-, and 15-degree Trendelenburg positions were as follows: 86.7 § 44.8, 104.3 § 54.5, 119.1 § 58.6, and 133.7 § 53.3 (p < 0.0001). CSA enlarged with the increase of Trendelenburg degree. Neither Trendelenburg position nor head rotation showed a correlation with overlap rate. Conclusions: Trendelenburg position significantly increased the CSA of the IJV, thus facilitating IJV cannulation. This new 3D reconstruction method permits the creation of a 3D volume through a tracked 2D ultrasound scanning system with image acquisition and integration and may prove useful in providing the user with a “road map” of the vascular anatomy of a patient’s neck or other anatomic structures. Ó 2019 Published by Elsevier Inc. Key Words: 2-dimensional tracked ultrasound; Trendelenburg position; head positioning; volume; location; internal jugular vein INTERNAL jugular vein (IJV) cannulation is performed fre- quently to access the central venous system. However, compli- cations can be life-threatening if the carotid artery (CA) or the lung is punctured. 1 The most commonly used approach by anes- thesiologists is ultrasound guidance with the patient in the head- down position (Trendelenburg position) with the head rotated 1 Address reprint requests to Daniel Bainbridge, MD, FRCPC, Department of Anesthesiology and Perioperative Medicine, Department of Medicine, Division of Critical Care, Western University, London, Ontario, Canada E-mail address: Daniel.Bainbridge@lhsc.on.ca (D. Bainbridge). # W. Wang and X. Liao contributed equally to this study. https://doi.org/10.1053/j.jvca.2019.08.049 1053-0770/Ó 2019 Published by Elsevier Inc. ARTICLE IN PRESS Journal of Cardiothoracic and Vascular Anesthesia 000 (2019) 16 Contents lists available at ScienceDirect Journal of Cardiothoracic and Vascular Anesthesia journal homepage: www.jcvaonline.com