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Patient specific modelling and optimization of the Dialysis therapy planning
No full textAbstract—Health conditions and quality of life of uremic
patients undergoing dialysis could be improved by a specific
tailoring of the haemodialysis (HD) treatment. This research
was aimed at optimising and customising the HD therapy in
order to improve the patients’ clinical outcome.
Two main goals have been pursued in order to reduce the
clinical intra HD patient distress and the medium to long term
HD related cardiovascular dysfunctions.
To achieve the first goal a patient-specific compartmental
model of the transport phenomena taking place in the patient
during the therapy has been developed, based on clinical data ad
hoc acquired. Three parameters, related to mass transfer at the
cell membrane, capillary wall permeability and thickness of the
protein layer inside the filters, were used to tune the model.
The comparison with the clinical data points out the model
ability in describing and predicting the patient-specific response
to HD with deviations always lower than 10%. The model allows
also the evaluation of the effects of different settings in terms of
catabolites removal efficiency.
The analysis of the clinical data also has allowed the
identification of two indexes correlated with the intra-HD
cardiac instabilities: HI allowing the evaluation of the patient’s
proneness to hypotension; PRI allowing the study of plasmarefilling
dynamics.
To achieve the second goal, a hybrid model of the
cardiovascular system has been developed, based on clinical
data of 20 patients waiting for the creation of the AVF and then
monitored after 10 days, 3 months, and 1 year from the fistula
tailoring. Here too, three parameters related to peripheral
vascular resistance (ξ), cardiac stiffness (q) and contractility (cc)
were used to adapt the model to each patient. The model
allowed the investigation of the alterations induced by the
presence of the AVF both in the short and the medium-long
period in terms of cardiac work, power, q, cc and ξ.
Summarizing, the developed models and the calculated
indexes help the customization of HD therapy and the reduction
of related co-morbidity. Based on these outputs the treatment
can be planned with more accuracy, bettering patients’ quality
of life and limiting cardiac overload
COMPARISON OF AEROSOL ACCESSORIES PERFORMANCES BY A FLUID DYNAMIC COMPUTATIONAL APPROACH
No full textCOMPUTATIONAL MODEL OF RED CELL FLOW IN MICRO-CHANNELS FOR PROBING MOLECULES ENCAPSULATION
No full textAim: Preliminary experiments confirm the possibility to load Red Blood Cells
(RBCs) with probing molecules (PM) by applying mechanical shear stresses
(τ) on RBCs stroma. This work is aimed at studying the optimal fluid dynamic
conditions allowing the encapsulation of PM into RBCs flowing in a microchannel
(MC).
Methods: A computational model was developed by using COMSOL Multiphysics
4.2a (Stockholm, Sweden). A 50 x 50 μm cross-section and 58.5 mm
length MC was considered. The Mixture Model was used to evaluate velocity (v),
volume fraction of dispersed phase (Id) and τ for a suspension of RBCs and PM
(FITC-Dextran) in a Phosphate Buffer.
When the pair of τ values and duration lays in the sub-haemolytic portion of the
Tillman Diagram, and the RBCs transit time into the MC is higher than the diffusion
characteristic time of PM into RBCs, encapsulation was promoted. The
flow rate Q, and the haematocrit Ht and MC size were tuned to optimise fluid
dynamic conditions and increase encapsulation.
Results: Optimal conditions were Q = 40 μl/min and Ht <0.15 with the modelled
MC. The resulting high pressure drop suggests to increase MC width (2000 μm)
by keeping constant height and length. The new optimal conditions were
Q = 1600 μl/min, 0.05<Ht<0.30. A normalized index (Ie) was defined as the
product of v, τ and rd; encapsulation is higher in the round crown region of the
MC section, where 0.8<Ie<1.
Conclusions: The developed model allows to characterize RBCs fluid dynamics
in MC and to identify the optimal conditions to promote PM encapsulation
into RBCs. This model will be used to design a new experimental set-up, defining
appropriate test conditions
Model of the physiological and pathological cardiovascular system with peripheral controls
No full textPatient-specific modelling of multi-compartment fluid and mass exchange during dialysis.
No full textTWO-POOL VIRTUAL PHYSICAL SIMULATOR TO REPRODUCE FLUID AND MASS TRANSFER DURING DIALYSIS
No full textAim: Hemodialysis (hd) induces fast changes of fluid volumes and electrolyte
concentrations in patients’ body compartments. The aim of this work is to
develop a two-pool virtual patient physical simulator (tvps) reproducing intracorporeal
transport phenomena during hd.
Methods: the main function of the tvps is to replicate the patient intra- and
extra-vascular compartments (ivc and evc). ivc is reproduced by a rigid reservoir
and a set of semi-permeable hollow fibers, representing the large arterial and
venous vessels and the capillary system respectively; evc is simulated by rigid
reservoirs, connected to a compliance. the hollow fibers are arranged in ad-hoc
designed modular filters, placed in the ivc. test fluids reproduces rheological
properties, oncotic pressure (by using polygelin and dextran), electrolytes and
catabolites contents of an uremic patient.
A Gambro AK200 machine was used to test the TVPS, performing a 3.5 hours
HD (average duration). Fluid samples were collected from TVPS at scheduled
intervals to evaluate the IVC and EVC solutes concentrations, for comparison
with clinical average data.
Results: All the electrolytes and urea concentrations showed good agreement
with clinical data (dextran: max shift 10%, polygelin: 20%). Plasmatic volume
profile showed good correlation with clinical patterns, also replicating the plasma-
refilling phenomenon.
Conclusions: The tests proved the TVPS capable to reproduce fluid and mass
transfer during HD. Such a system would be useful to characterize commercial
or new dialyzers, accounting for the dynamic effects of mass transport induced
by the patient-machine interaction
Development of a two-pool virtual simulator of fluid and mass transfer in a dialysis patient
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