Castiglioni P, Di Rienzo M, Grossoni M, Tommasini R, Morpurgo M
LaRC-Centro di Bioingegneria, Milan, Italy.
Eur Respir J. 1996 Nov;9(11):2328-34. doi: 10.1183/09031936.96.09112328.
The aim of this study was to determine whether spontaneous respiration influences pulmonary artery input impedance, a question that has received little attention in the literature. Impedance values were assessed during three different phases of the respiratory cycle, namely inspiration, expiration and postexpiration (i.e. the null respiratory flow period between expiration and the next inspiration) in five anaesthetized spontaneously breathing dogs. Firstly, impedance values during postexpiration were taken as the reference baseline, and compared with values obtained during inspiration and expiration. Then, differences between values in inspiration and in expiration were tested, taking impedance during inspiration as the baseline. Differences with respect to postexpiration were found for three parameters of input impedance: input resistance, characteristic impedance, and the frequency at the first zero-crossing of the impedance phase from negative to positive values (f(cross)). Input resistance was significantly lower in inspiration (85% of the baseline), characteristic impedance was significantly greater in inspiration and in expiration (112 and 119% respectively), and f(cross) was significantly lower in expiration (89%). By contrast, only input resistance differed significantly when inspiration was compared to expiration. Therefore, spontaneous respiration was shown to influence input impedance significantly. The observed changes in characteristic impedance and f(cross) might be explained by a stiffening of the pulmonary artery wall, due to neural and/or mechanical factors, during inspiration and expiration.
本研究的目的是确定自主呼吸是否会影响肺动脉输入阻抗，这一问题在文献中很少受到关注。在五只麻醉状态下自主呼吸的犬中，于呼吸周期的三个不同阶段（即吸气、呼气和呼气后，呼气后是指呼气与下一次吸气之间的零呼吸流期）评估阻抗值。首先，将呼气后的阻抗值作为参考基线，并与吸气和呼气期间获得的值进行比较。然后，以吸气期间的阻抗为基线，测试吸气和呼气时的值之间的差异。在输入阻抗的三个参数方面发现了与呼气后相比的差异：输入电阻、特性阻抗以及阻抗相位从负值变为正值时的第一个过零点频率（f(cross)）。吸气时输入电阻显著降低（为基线的85%），吸气和呼气时特性阻抗显著增大（分别为112%和119%），呼气时f(cross)显著降低（为89%）。相比之下，当比较吸气和呼气时，只有输入电阻有显著差异。因此，自主呼吸被证明会显著影响输入阻抗。观察到的特性阻抗和f(cross)的变化可能是由于吸气和呼气期间神经和/或机械因素导致肺动脉壁变硬所致。
