Burattini R, Campbell K B
Department of Electronics and Automatica, University of Ancona, Italy.
Am J Physiol. 1993 Jun;264(6 Pt 2):H1977-87. doi: 10.1152/ajpheart.1993.264.6.H1977.
To estimate descending thoracic aortic compliance in anesthetized open-chest dogs, a modified T-tube arterial model was used. This model consists of two uniform and lossless elastic tubes, one representing arteries going toward the head and upper limbs and the other (body tube) representing descending aortic circulation to the trunk and lower limbs. Each tube terminates with a generalized first-order low-pass filter load. Pressure and flow in the ascending aorta and flow in the upper descending aorta were measured and used to estimate model parameters. Using the estimated model parameters, we calculated the pressure waveshape at the termination of the body tube. Comparison of this model-predicted pressure with pressure measured in the abdominal aorta near the origin of renal arteries suggested that the end of the body tube (effective reflecting site of the body circulation) corresponds to this major branching site of the abdominal aorta. To calculate the length of the body tube, we used aortic pulse wave velocity estimated from the measurements of pressure in ascending and abdominal aorta. Calculated body tube length averaged 30.3 +/- 2.8 cm and approximated the measured length (30.6 +/- 3.0 cm) of the aorta from the arch to the region of the origin of renal arteries. Compliance of the body tube averaged 123 +/- 20 x 10(-6) g-1.cm4.s2 and was interpreted as the descending thoracic aortic compliance. The ratio of this compliance to the body tube length gave an estimate of the effective distributed compliance, i.e., the compliance per unit length that would be observed in the absence of tapering. This ratio averaged 4.10 +/- 0.86 x 10(-6) g-1.cm3.s2 and fell in between the values of local aortic compliance independently estimated along the descending thoracic aorta from measurements of pressure and diameter. Thus tube compliance resulted in a physically identifiable property. This property was contrasted with the ill-defined effective compliances of the terminal loads.
为了评估麻醉开胸犬降主动脉的顺应性，使用了一种改良的T形管动脉模型。该模型由两根均匀且无损耗的弹性管组成，一根代表通向头部和上肢的动脉，另一根（体循环管）代表降主动脉至躯干和下肢的循环。每根管子末端都有一个广义一阶低通滤波器负载。测量升主动脉的压力和流量以及降主动脉上段的流量，并用于估计模型参数。利用估计的模型参数，计算体循环管末端的压力波形。将该模型预测的压力与肾动脉起始部附近腹主动脉测量的压力进行比较，结果表明体循环管末端（体循环的有效反射部位）对应于腹主动脉的这一主要分支部位。为了计算体循环管的长度，我们使用了根据升主动脉和腹主动脉压力测量值估算的主动脉脉搏波速度。计算得到的体循环管长度平均为30.3±2.8 cm，与从主动脉弓到肾动脉起始部位测量的主动脉长度（30.6±3.0 cm）相近。体循环管的顺应性平均为123±20×10⁻⁶ g⁻¹·cm⁴·s²，被解释为降主动脉的顺应性。该顺应性与体循环管长度的比值给出了有效分布顺应性的估计值，即在不存在管径逐渐变细的情况下每单位长度的顺应性。该比值平均为4.10±0.86×10⁻⁶ g⁻¹·cm³·s²，介于沿降主动脉通过压力和直径测量独立估算的局部主动脉顺应性值之间。因此，管顺应性产生了一种物理上可识别的特性。该特性与终端负载定义不明确的有效顺应性形成对比。
