The effect of body position on developing ultrasound criteria for the assessment of the internal jugular vein.

Recent studies investigating chronic cerebrospinal venous insufficiency highlighted that intracranial venous return has not yet been routinely investigated by ultrasound in the normal population. This creates an absence of a reference standard and raises concerns that the approach introduces variations into the results. The primary objective of this study was to develop reference standards for the assessment of the internal jugular vein in a normal population. A prospective small-scale study was conducted. Internal jugular veins of 31 normal candidates were examined using B-Mode and PW Doppler. Measurements at proximal and mid-point internal jugular vein were taken in sitting (90°) and supine (0°) positions. Area measurements were taken during passive respiration in cm(2). Time average velocity measurements were taken during passive respiration over a 3-second period. Reflux measurements were taken after apnoea and reflux was recorded from any reversed flow. Measurements were taken three times; an average was calculated and statically analysed. Of the 31 participants, one was excluded from the study and 30 were suitable. The Mann-Whitney U test was used to analyse the results; all results (area, time average velocity and reflux) showed that there was a significant difference between the two positions with p < 0.05 (two-tailed). This pilot study does suggest that there is a significant difference in area, time average velocity and reflux measurements of the internal jugular vein when taken in the sitting and supine position, which could affect the outcome of chronic cerebrospinal venous insufficiency. A further large-scale study is required to validate and standardise the assessment of the internal jugular vein.