A LUMPED PARAMETER MODEL OF VASCULAR PERIPHERIES FOR CKD PATIENTS: A STEP TOWARDS MULTISCALE MODELLING

Objectives: Microvascular impairment has been reported in CKD patients, especially in patients undergoing hemo- dialysis. To study these phenomena, we already develop a computational model allowing the description of fluid homeostasis at the microscale and a lumped parameter model of the vascular system. The intention is to approach the problem at different scales and in this view the here presented description of peripheral districts. Methods: Starting for a previous lumped parameter model of the vasculature, we improve the peripheral districts descrip- tion including: (i) a rheology of blood in small vessel strain rate dependent using Casson’s model, (ii) a better lymphatic description, (iii) mechanical effect of fluid filtration, myo- genic and metabolic controls along with the shear stresses effect, integrating different literature information. Results: Tests performed on a single periphery both with constant and variable flow rate (based on data from the previous entire model) results in: (i) fluid accumulation within the interstitial space if the contribution of lymphatic system is not considered; (ii) highlighting the effect of peripheral controls in response to different input flow rate; (iii) estimating factors involved in fluid balance at the microvascular level, such as hydraulic and oncotic pres- sure for both capillaries and interstitium. Discussion and Conclusion: This work highlights the key role of both lymphatic system and peripheral vascular controls. Accounting for those contributions, the lumped parameter model allows estimating values of the input variables of the microscale model. Such information are difficulty retrieved clinically and their estimation is not simple due to the complexity of the phenomenon; however this type of analysis is essential to study microvascular impairment in CKD patients. In conclusion, this work rep- resents a step towards a multiscale model of the vascula- ture for CKD patients.