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Abstract：
The notion of a constant relationship between resistance and capacitance (RC time) in the pulmonary circulation has been challenged by more recent research. The RC time can be obtained using either a simplified empirical approach or a semilogarithmic equation. Although direct curve-fit analysis is a feasible and ostensibly reference approach for RC analysis, it remains largely unexplored. We aimed to study the relationship between various RC methods in different states of pulmonary hemodynamics. Methods In total, 182 patients underwent clinically indicated right heart catheterization. The pressure curves were exported and processed using the MATLAB software. We calculated the RC time using the empirical method (RCEST), semilogarithmic approach (RCSL), and direct measurement of curve fit (RCFIT). Results Among 182 patients, 137 had pulmonary hypertension due to left heart disease (PH-LHD), 35 had pulmonary arterial hypertension (PAH), and 10 demonstrated normal hemodynamics (non-PH). RCEST consistently overestimated the RCFIT and RCSL measurements by a mean of 75%. With all three methods, the RC values were longer in the PAH (RCFIT = 0.36 ± 0.14 s) than in the PH-LHD (0.27 ± 0.1 s) and non-PH (0.27 ± 0.09 s) groups (p < 0.001). Although the RCSL and RCFIT values were similar among the three subgroups, they exhibited broad limits of agreement. Finally, the RCEST demonstrated a strong discriminatory ability (AUC = 0.86, p < 0.001, CI = 0.79-0.93) in identifying PAH. Conclusion RC time in PAH patients was substantially prolonged compared to that in PH-LHD and non-PH patients. The use of the empirical formula yielded systematic RC overestimation. In contrast, the semilogarithmic analysis provided reliable RC estimates, particularly for group comparisons.
摘要：
肺循环中电阻和电容（RC时间）之间恒定关系的概念受到了最近研究的挑战。可以使用简化的经验方法或半对数方程来获得RC时间。尽管直接曲线拟合分析是RC分析的一种可行且表面上可参考的方法，它在很大程度上仍未被探索。我们旨在研究不同肺血流动力学状态下各种RC方法之间的关系。方法总计,182例患者接受了临床指示的右心导管插入术。使用MATLAB软件导出并处理压力曲线。我们使用经验方法(RCEST)计算了RC时间，半对数方法(RCSL)，和直接测量曲线拟合(RCFIT)。结果182例患者中,137例由于左心疾病（PH-LHD）导致肺动脉高压，35人患有肺动脉高压（PAH），和10显示正常的血液动力学（非PH）。RCEST始终高估了RCFIT和RCSL测量值的平均值为75％。这三种方法,PAH组(RCFIT=0.36±0.14s)的RC值比PH-LHD组(0.27±0.1s)和非PH组(0.27±0.09s)的RC值长(p<0.001).尽管三个亚组的RCSL和RCFIT值相似，他们表现出广泛的共识。最后,RCEST在鉴别PAH方面表现出较强的鉴别能力(AUC=0.86,p<0.001,CI=0.79-0.93)。结论与PH-LHD和非PH患者相比，PAH患者的RC时间明显延长。经验公式的使用产生了系统的RC高估。相比之下,半对数分析提供了可靠的RC估计，特别是小组比较。
