Effect of head and shoulder positioning on the cross-sectional area of the subclavian vein in obese subjects.

Abstract

Head and shoulder positioning may affect cross-sectional area (CSA) and location of the subclavian vein (SCV). We investigated the CSA of the SCV and the depth of the SCV, depending on the head and shoulder positions. In 24 healthy obese volunteers, the short axis ultrasound images of the SCV and adjacent structures were obtained in three different head positions (neutral, 30° turned to the contralateral side, and 30° turned to the ipsilateral side) and two different shoulder positions (neutral and lowered). Images of the right and left SCVs were obtained in the supine and Trendelenburg positions. Subsequently, the CSA and depth of the SCV were measured. Significant differences were found in the CSA of the SCV in different head positions (30° turned to contralateral side vs. neutral: -0.06cm2, 95% confidence interval [CI], -0.10 to -0.02; Pcorrected=0.002, 30° turned to contralateral side vs. 30° turned to ipsilateral side: -0.16cm2, 95% CI, -0.22 to -0.11; Pcorrected<0.001, Neutral vs. 30° turned to ipsilateral side: -0.10cm2, 95% CI, -0.14 to -0.07; Pcorrected<0.001). The CSA of the SCV was significantly different, depending on shoulder positions (neutral vs. lowered: 0.44cm2, 95% CI, 0.33 to 0.54; Pcorrected<0.001), and body position (supine vs. Trendelenburg: -0.15cm2, 95% CI, -0.19 to -0.12; Pcorrected<0.001). However, the depth of the SCV did not differ with respect to head, shoulder, and body positions. Ipsilateral 30° head rotation, neutral shoulder position, and Trendelenburg position significantly enhanced the CSA of the SCV in obese participants.