McKinney M E, Buell J C, Eliot R S
Aviat Space Environ Med. 1984 Oct;55(10):893-5.
A recent publication noted that women and men differ in transthoracic impedance (Zo), with women having higher levels, and this might cause underestimation of stroke volume index (SVI) in women when impedance cardiograph (IC) techniques are employed, as Zo is a squared factor in the denominator of the calculation equation. This paper confirmed the observed sex differences in Zo, with women (n = 19) having significantly (p less than 0.0001) higher Zo than men (n = 19) in both seated and supine positions. However, women also had higher dZ/dt (first derivative of impedance signal over time) levels when seated (women: 2.48 +/- 0.58; men: 1.38 +/- 0.35; p less than 0.0001) and when supine (women: 2.62 +/- 0.56; men: 1.58 +/- 0.34; p less than 0.0001). dZ/dt is a factor in the numerator, and, therefore, calculated SVI did not differ across sexes in either position. It was speculated that the Zo difference is due to differences in fat levels. Controlling for percent body fat and subscapula skin-fold differences did not entirely eliminate the sex differences in Zo. However, a group of well-trained females tested later (n = 10) showed lower Zo levels (24.8 vs. 28.2) when compared to the original group of 19 women who were not well-trained. Differences may be due to fat/muscle ratio of the thorax.
最近的一项出版物指出，女性和男性的经胸阻抗（Zo）存在差异，女性的水平更高，当采用阻抗心动图（IC）技术时，这可能会导致女性的每搏输出量指数（SVI）被低估，因为Zo是计算方程分母中的平方因子。本文证实了在Zo方面观察到的性别差异，在坐姿和仰卧位时，女性（n = 19）的Zo均显著（p小于0.0001）高于男性（n = 19）。然而，女性在坐姿（女性：2.48±0.58；男性：1.38±0.35；p小于0.0001）和仰卧位（女性：2.62±0.56；男性：1.58±0.34；p小于0.0001）时的dZ/dt（阻抗信号随时间的一阶导数）水平也更高。dZ/dt是分子中的一个因子，因此，在任一位置计算出的SVI在性别之间没有差异。据推测，Zo的差异是由于脂肪水平的差异。控制体脂百分比和肩胛下皮褶差异并不能完全消除Zo的性别差异。然而，与最初未经良好训练的19名女性组相比，后来测试的一组训练有素的女性（n = 10）显示出较低的Zo水平（24.8对28.2）。差异可能归因于胸部的脂肪/肌肉比例。
