Lu W, Tsukada A, Kawarada A, Sasaki K
Division of Bio-Information Engineering, Faculty of Engineering, Toyama University, Japan.
Front Med Biol Eng. 1999;9(1):9-29.
Using a finite element method (FEM) and a volume oscillometric method with a photo-electric plethysmograph, we tried to determine which location(s) and which bladder width(s) of the occluding cuff would allow the most accurate indirect blood pressure measurements at the human wrist. Nuclear magnetic resonance imaging of the wrist allowed us to determine the geometry of two-dimensional (2D) finite element models. FEM analysis showed that the pressure transmission ratio (calculated tissue pressure: externally applied pressure) from the cuff to the radial artery (RA) was 100% when the cuff was placed over the site (L1) at which the RA crosses the most protuberant spot on the volar aspect of the distal end of the radius. In fact, the mean blood pressure (BPM) measured at this site in human subjects coincided with that measured at the upper arm (BPMA). In addition, a three-dimensional (3D) FEM was constructed by extending the 2D FEM at site L1 in the longitudinal direction to investigate the relation between pressure transmission to the RA and cuff bladder width. FEM analysis using the 3D finite element model showed that for all cuff widths greater than 0.25 times the diameter of the wrist, the external pressure was transmitted almost completely to the RA beneath the cuff center. Moreover, when the cuff width was as large as 0.45 times the diameter of the wrist, the BPM measured at site L1 in human subjects was similar to the BPMA. The theoretical and experimental results in the present study both suggest that for accurate indirect blood pressure measurements at the wrist, the L1 site is a suitable location for the occluding cuff and a cuff whose bladder width is more than one-third but less than one-half the wrist diameter can be used.
我们使用有限元方法（FEM）和结合光电体积描记法的容积示波法，试图确定阻塞袖带的哪些位置和哪些宽度能够在人体手腕处实现最准确的间接血压测量。手腕的核磁共振成像使我们能够确定二维（2D）有限元模型的几何形状。有限元分析表明，当袖带放置在桡动脉（RA）穿过桡骨远端掌侧最突出点的位置（L1）时，从袖带至桡动脉的压力传递比（计算得出的组织压力：外部施加压力）为100%。实际上，在人体受试者的该部位测得的平均血压（BPM）与在上臂测得的血压（BPMA）一致。此外，通过在纵向方向上扩展L1部位的二维有限元模型构建了三维（3D）有限元模型，以研究向桡动脉的压力传递与袖带气囊宽度之间的关系。使用三维有限元模型进行的有限元分析表明，对于所有大于手腕直径0.25倍的袖带宽度，外部压力几乎完全传递至袖带中心下方的桡动脉。此外，当袖带宽度达到手腕直径的0.45倍时，在人体受试者L1部位测得的BPM与BPMA相似。本研究的理论和实验结果均表明，为在手腕处进行准确的间接血压测量，L1部位是阻塞袖带的合适位置，并且可以使用气囊宽度大于手腕直径三分之一但小于二分之一的袖带。
