Pietribiasi Mauro, Waniewski Jacek, Załuska Alicja, Załuska Wojciech, Lindholm Bengt
Institute of Biocybernetics and Biomedical Engineering, Warsaw, Poland.
Department of Rehabilitation and Physiotherapy, Medical University of Lublin, Lublin, Poland.
PLoS One. 2016 Aug 2;11(8):e0159748. doi: 10.1371/journal.pone.0159748. eCollection 2016.
The kinetics of protein transport to and from the vascular compartment play a major role in the determination of fluid balance and plasma refilling during hemodialysis (HD) sessions. In this study we propose a whole-body mathematical model describing water and protein shifts across the capillary membrane during HD and compare its output to clinical data while evaluating the impact of choosing specific values for selected parameters.
The model follows a two-compartment structure (vascular and interstitial space) and is based on balance equations of protein mass and water volume in each compartment. The capillary membrane was described according to the three-pore theory. Two transport parameters, the fractional contribution of large pores (αLP) and the total hydraulic conductivity (LpS) of the capillary membrane, were estimated from patient data. Changes in the intensity and direction of individual fluid and solute flows through each part of the transport system were analyzed in relation to the choice of different values of small pores radius and fractional conductivity, lymphatic sensitivity to hydraulic pressure, and steady-state interstitial-to-plasma protein concentration ratio.
The estimated values of LpS and αLP were respectively 10.0 ± 8.4 mL/min/mmHg (mean ± standard deviation) and 0.062 ± 0.041. The model was able to predict with good accuracy the profiles of plasma volume and serum total protein concentration in most of the patients (average root-mean-square deviation < 2% of the measured value).
The applied model provides a mechanistic interpretation of fluid transport processes induced by ultrafiltration during HD, using a minimum of tuned parameters and assumptions. The simulated values of individual flows through each kind of pore and lymphatic absorption rate yielded by the model may suggest answers to unsolved questions on the relative impact of these not-measurable quantities on total vascular refilling and fluid balance.
蛋白质进出血管腔室的动力学在血液透析（HD）过程中体液平衡和血浆再充盈的决定中起主要作用。在本研究中，我们提出了一个全身数学模型，描述HD过程中跨毛细血管膜的水和蛋白质转移，并将其输出结果与临床数据进行比较，同时评估选择特定参数值的影响。
该模型采用双室结构（血管和间质空间），基于每个腔室中蛋白质质量和水体积的平衡方程。根据三孔理论描述毛细血管膜。从患者数据中估计两个转运参数，即大孔的分数贡献（αLP）和毛细血管膜的总水力传导率（LpS）。分析了通过转运系统各部分的单个流体和溶质流动的强度和方向变化与小孔半径、分数传导率、淋巴管对液压的敏感性以及稳态间质与血浆蛋白浓度比的不同值的选择之间的关系。
LpS和αLP的估计值分别为10.0±8.4 mL/min/mmHg（平均值±标准差）和0.062±0.041。该模型能够以良好的准确性预测大多数患者的血浆体积和血清总蛋白浓度曲线（平均均方根偏差<测量值的2%）。
所应用的模型使用最少的调整参数和假设，对HD期间超滤引起的流体转运过程提供了一种机理解释。该模型得出的通过每种孔的单个流量和淋巴管吸收率的模拟值，可能为这些不可测量量对总血管再充盈和体液平衡的相对影响这一未解决问题提供答案。
