Implementation of an Automated Peripheral Resistance Device in a Mock Circulatory Loop With Characterization of Performance Values Using Simulink Simscape and Parameter Estimation

2012 ◽  
Vol 6 (4) ◽  
Author(s):  
Charles E. Taylor ◽  
Gerald E. Miller
Keyword(s):  
Parameter Estimation ◽  
Heart Valves ◽  
Water Solution ◽  
Peripheral Resistance ◽  
Ventricular Assist Devices ◽  
Experimental Conditions ◽  
Ventricular Assist

Accurate peripheral resistance simulation in a mock circulatory loop is critical to the evaluation of ventricular assist devices and heart valves. Implementation of an automated device that is capable of accurate resistance settings and precise reproduction of cardiovascular parameters allows for improved construction of experimental conditions within a mock circulatory loop. A mock circulatory loop resistor that employs a proportional valve design is proposed; a piston extending into the flow path to produce a resistance to flow. Real-time position feedback of the piston is used to determine orifice size, providing resolution in the change of resistance over time. Characterization of the physical system with The MathWorks SIMULINK™ SIMSCAPE™ block set allowed the determination of objective device parameters; the discharge coefficient and critical Reynolds number. The determination of these values was achieved utilizing the SIMULINK™ Parameter Estimation™ tool, experimental data, and a computational plant model of the experimental setup. With this information, an accurate computational model of the resistance device is presented for use in determining resistance settings in silico prior to implementation in the mock circulatory loop. Experimental in vitro trials verified the repeatability of the automated resistor performance by means of a staircase testing of piston position during several different continuous flow rates of a glycerin/water solution.

Evaluation of Platelet Activation Models With Dynamic Shear Stress In Vitro Experiments

2012 ◽  
Author(s):  
Jawaad Sheriff ◽  
Michalis Xenos ◽  
João S. Soares ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Relative Paucity ◽  
Valvular Diseases ◽  
End Stage

Blood recirculating devices, which include ventricular assist devices and prosthetic heart valves, are necessary for some patients suffering from end-stage heart failure and valvular diseases. However, disturbed flow patterns in these devices cause shear-induced platelet activation and aggregation. Thromboembolic complications resulting from this platelet behavior necessitates lifelong anticoagulant therapy for patients implanted with such devices. In addition, blood recirculating device manufacturers mostly test and optimize their products for hemolysis, which occurs at shear stresses ten-fold higher than required for platelet activation. The relative paucity of optimization for flow-induced thrombogenicity is further exacerbated by the fact that there are few predictive shear-induced platelet activation models.

Dynamic Shear Stress Induced Platelet Activation in Blood Recirculation Devices: Implications for Thrombogenicity Minimization

2009 ◽  
Author(s):  
Gaurav Girdhar ◽  
Jawaad Sheriff ◽  
Michalis Xenos ◽  
Yared Alemu ◽  
Thomas Claiborne ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Activation ◽  
Heart Valves ◽  
Total Artificial Heart ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Bridge To Transplant ◽  
End Stage ◽  
Effective Design

Implantable blood recirculation devices such as ventricular assist devices (VADs) and more recently the temporary total artificial heart (TAH-t) are promising bridge-to-transplant (BTT) solutions for patients with end-stage cardiovascular disease. However, blood flow in and around certain non-physiological geometries, mostly associated with pathological flow around mechanical heart valves (MHVs) of these devices, enhances shear stress-induced platelet activation, thereby significantly promoting flow induced thrombogenicity and subsequent complications such as stroke, despite a regimen of post-implant antithrombotic agents. Careful characterization of such localized high shear stress trajectories in these devices by numerical techniques and corresponding experimental measurements of their accentuated effects on platelet activation and sensitization, is therefore critical for effective design optimization of these devices (reducing the occurrence of pathological flow patterns formation) for minimizing thrombogenicity [1].

Characterization of the Serum a1-Antitripsine Level in Primary Spontaneous Pneumotorax Patients

2018 ◽  
Vol 69 (9) ◽  
pp. 2591-2593
Author(s):  
Cristina Grigorescu ◽  
Liviu Ciprian Gavril ◽  
Laura Gavril ◽  
Tiberiu Lunguleac ◽  
Bogdan Mihnea Ciuntu ◽  
...  
Keyword(s):  
Serum Level ◽  
Pulmonary Emphysema ◽  
Spontaneous Pneumothorax ◽  
Antitrypsin Deficiency ◽  
Alpha 1 Antitrypsin Deficiency ◽  
Alpha 1 Antitrypsin ◽  
Determining Factor

Diagnosis of primary or idiopathic spontaneous pneumothorax is one of exclusion, and in fact defines an entity that may have a difficult or impossible cause to be highlighted by current means, we consider it appropriate to study these etiopathogenic aspects. There is a definite association between alpha-1 antitrypsin deficiency and pulmonary emphysema and indirect spontaneous pneumothorax secondary to an emphysematous pulmonary lesion. Dose of alpha-1 antitrypsin is an immunoturbinimetric method for in vitro determination of alpha-1 antitrypsin in human serum and plasma. This product is calibrated to be used for the Daytona RX analyzer. The serum level of alpha-1-antitrypsin is not a determining factor in the postoperative evolution characterized by the interval until air loss disappears, but certainly exerts some influence, the exact level of which remains to be determined.

Factors affecting in vitro and in vivo antioxidant effects. Experimental conditions and nature of oxidants determine antioxidant efficacy

2021 ◽  
pp. 1-9
Author(s):  
Etsuo Niki
Keyword(s):  
Biological Molecules ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Beneficial Effects ◽  
Multiple Oxidants ◽  
Antioxidant Effects

Reactive oxygen and nitrogen species have been implicated in the onset and progression of various diseases and the role of antioxidants in the maintenance of health and prevention of diseases has received much attention. The action and effect of antioxidants have been studied extensively under different reaction conditions in multiple media. The antioxidant effects are determined by many factors. This review aims to discuss several important issues that should be considered for determination of experimental conditions and interpretation of experimental results in order to understand the beneficial effects and limit of antioxidants against detrimental oxidation of biological molecules. Emphasis was laid on cell culture experiments and effects of diversity of multiple oxidants on antioxidant efficacy.

scholarly journals Response of a physiological controller for ventricular assist devices during acute patho-physiological events: an in vitro study

2017 ◽  
Vol 62 (6) ◽  
pp. 623-633 ◽  
Author(s):  
Anastasios Petrou ◽  
Panagiotis Pergantis ◽  
Gregor Ochsner ◽  
Raffael Amacher ◽  
Thomas Krabatsch ◽  
...  
Keyword(s):  
Valsalva Maneuver ◽  
Constant Speed ◽  
Ventricular Assist Devices ◽  
Moving Window ◽  
Clinical Implementation ◽  
Premature Ventricular Contractions ◽  
Ventricular Assist ◽  
Assist Devices ◽  
Mock Circulation

AbstractThe current paper analyzes the performance of a physiological controller for turbodynamic ventricular assist devices (tVADs) during acute patho-physiological events. The numerical model of the human blood circulation implemented on our hybrid mock circulation was extended in order to simulate the Valsalva maneuver (VM) and premature ventricular contractions (PVCs). The performance of an end-diastolic volume (EDV)-based physiological controller for VADs, named preload responsive speed (PRS) controller was evaluated under VM and PVCs. A slow and a fast response of the PRS controller were implemented by using a 3 s moving window, and a beat-to-beat method, respectively, to extract the EDV index. The hemodynamics of a pathological circulation, assisted by a tVAD controlled by the PRS controller were analyzed and compared with a constant speed support case. The results show that the PRS controller prevented suction during the VM with both methods, while with constant speed, this was not the case. On the other hand, the pump flow reduction with the PRS controller led to low aortic pressure, while it remained physiological with the constant speed control. Pump backflow was increased when the moving window was used but it avoided sudden undesirable speed changes, which occurred during PVCs with the beat-to-beat method. In a possible clinical implementation of any physiological controller, the desired performance during frequent clinical acute scenarios should be considered.

In-vitro characterization of flow through mechanical heart valves

2006 ◽  
Vol 39 ◽  
pp. S306 ◽  
Author(s):  
L.P. Dasi ◽  
H. Simon ◽  
L. Ge ◽  
F. Sotiropoulos ◽  
A. Yoganathan
Keyword(s):  
Heart Valves ◽  
Mechanical Heart Valves ◽  
In Vitro Characterization ◽  
Flow Through

Design Optimization of a Mechanical Heart Valve for Reducing Valve Thrombogenicity: A Case Study With ATS Valve

2010 ◽  
Author(s):  
Gaurav Girdhar ◽  
Yared Alemu ◽  
Michalis Xenos ◽  
Jawaad Sheriff ◽  
Jolyon Jesty ◽  
...  
Keyword(s):  
Heart Valves ◽  
Thrombus Formation ◽  
Anticoagulation Therapy ◽  
Mechanical Heart Valve ◽  
Ventricular Assist Devices ◽  
Circulatory Support ◽  
Ventricular Assist ◽  
Mechanical Circulatory Support Devices ◽  
Artificial Hearts

Flow past mechanical heart valves (MHV) in mechanical circulatory support devices including total artificial hearts and ventricular assist devices, is primarily implicated in thromboembolism due to non-physiological flow conditions where the elevated stresses and exposure times are sufficiently high to cause platelet activation and thrombus formation. Mitigation of this risk requires lifelong anticoagulation therapy and less thrombogenic MHV designs should therefore be developed by device manufacturers [1].

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