Tardy Y, Meister J J, Perret F, Brunner H R, Arditi M
Department of Physics, Swiss Federal Institute of Technology, Ecublens, Switzerland.
Clin Phys Physiol Meas. 1991 Feb;12(1):39-54. doi: 10.1088/0143-0815/12/1/003.
The non-linear elastic response of arteries implies that their mechanical properties depend strongly on blood pressure. Thus, dynamic measurements of both the diameter and pressure curves over the whole cardiac cycle are necessary to characterise properly the elastic behaviour of an artery. We propose a novel method of estimating these mechanical properties based on the analysis of the arterial diameter against pressure curves derived from ultrasonic and photoplethysmographic measurements. An ultrasonic echo tracking device has been developed that allows continuous recording of the internal diameter of peripheral arteries. It measures the diameter 300 times per second with a resolution of 2.5 microns. This system is linked to a commercially available light-plethysmograph which continuously records the finger arterial pressure (0.25 kPa accuracy). Because of the finite pulse wave velocity, the separation between the diameter and the pressure measurement sites causes a hysteresis to appear in the recorded diameter-pressure curve. Using a model based on haemodynamic considerations, the delay between the diameter variations and the finger arterial pressure is first eliminated. As the pulse wave velocity depends on the pressure, the delay is determined for each pressure value. The relationship between pressure and diameter is then described by a non-linear mathematical expression with three parameters, which best fits the recorded data. The dynamic local behaviour of the vessel is fully characterised by these parameters. Compliance, distensibility and pulse wave velocity can then be calculated at each pressure level. Thus, the mechanical behaviour of peripheral human arteries can now be characterised non-invasively over the pressure range of the whole cardiac cycle. The results obtained in vivo on human radial and brachial arteries show that a thorough analysis of the compliance-pressure curves and their modifications (curving, shift) is needed in order to compare two different vessels in a meaningful way.
动脉的非线性弹性反应意味着其力学特性强烈依赖于血压。因此，在整个心动周期中对直径和压力曲线进行动态测量，对于准确表征动脉的弹性行为是必要的。我们基于对由超声和光电容积描记测量得出的动脉直径与压力曲线的分析，提出了一种估算这些力学特性的新方法。已开发出一种超声回波跟踪装置，可连续记录外周动脉的内径。它每秒测量直径300次，分辨率为2.5微米。该系统与市售的光电容积描记仪相连，后者可连续记录手指动脉压力（精度为0.25 kPa）。由于脉搏波速度有限，直径和压力测量部位之间的距离会导致记录的直径 - 压力曲线出现滞后现象。使用基于血流动力学考虑的模型，首先消除直径变化与手指动脉压力之间的延迟。由于脉搏波速度取决于压力，针对每个压力值确定延迟。然后用具有三个参数的非线性数学表达式描述压力与直径之间的关系，该表达式最适合记录的数据。这些参数充分表征了血管的动态局部行为。然后可以在每个压力水平计算顺应性、扩张性和脉搏波速度。因此，现在可以在整个心动周期的压力范围内，以非侵入性方式表征人体外周动脉的力学行为。在人体桡动脉和肱动脉上获得的体内结果表明，为了有意义地比较两条不同的血管，需要对顺应性 - 压力曲线及其变化（弯曲、偏移）进行全面分析。
