左心室每搏出量的估算

Estimation of Left Ventricular Stroke Volume

为了更准确地估算左心室功能指标，作者根据胸腔并联导体模型和准线性弹性腔模型，从理论上得到了用胸阻抗法测算心搏出量（ＳＶ）的新算式：ＳＶ＝Ｋρ（Ｌ／Ｚ０）２△Ｚ。与Ｎｙｂｏｅｒ理论所得到的心搏出量的公式：ＳＶ＝Ｋρ（Ｌ／Ｚ０）２△Ｚ所不同的是，改进后的新算式中，心搏出量不仅与胸阻抗的变化量（△Ｚ）有关，而且还与时间因子Ｋ有关。时间因子Ｋ定义为心动周期（Ｔ）与舒张期持续时间（Ｔｄ）之比。

In order to accurately estimate parameters of left ventricular function, a new stroke volume equation for thoracic electrical bioimpedance is proposed in this paper. This theoretically derived formula is based on both the quasi-linear Windkessel model and the parallel conductor model. The new stroke volume equation can be expressed as: SV=Kp (L/Z0)2△Z. It differs from Nyboer equation in that the stroke volume not only depends on the maximum value of the transthoracic impedance changes(△Z), but also on the time factor(K). K is defined as the ratio of cardiac period(T) to total duration of diastole(Td).