Letter Re: Internal jugular and vertebral vein volume flow in patients with clinically isolated syndrome or mild multiple sclerosis and healthy controls: results from a prospective sonographer-blinded study

摘要

In the discussion section of the paper "Internal jugular and vertebral vein volume flow in patients with clinically isolated syndrome or mild multiple sclerosis and healthy controls: results from a prospective sonogra-pher-blinded study", the authors face the potential criticism regarding the validity of the method for estimating volume flow, and conclude that the method they followed to estimate the blood flow by using vein diameter instead of using the cross sectional area (CSA) introduces a systematic error.1 We believe that, for collapsible tubes, this assertion is true only when certain conditions are met. In fact, the relationship between the area at equilibrium (p_i=p_e) A_0 and the actual area A of the internal jugular vein (IJV) depends on the Young modulus (E) of the tissue, on the Poisson's ratio (v) and on the external pressure (p_e) acting on the vein, and it is expressed by the following equation2'3