Performance Evaluation of Geometrically Different Pediatric Arterial Cannulae in a Pediatric Cardiopulmonary Bypass Model

ABSTRACT Objective: To define a reference chart comparing pressure drop vs. flow generated by a set of arterial cannulae currently utilized in cardiopulmonary bypass conditions in pediatric surgery. Methods: Cannulae from two manufacturers were selected considering their design and outer and inner diameters. Cannula performance was evaluated in terms of pressure drop vs. flow during simulated cardiopulmonary bypass conditions. The experimental circuits consisted of a Jostra HL-20 roller pump, a Quadrox-i pediatric oxygenator (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set. The circuit was primed with lactated Ringer's solution only (first condition) and with human packed red blood cells added (second condition) to achieve a hematocrit of 30%. Cannula sizes 8 to 16 Fr were inserted into the cardiopulmonary bypass circuit with a "Y" connector. The flow was adjusted in 100 ml/min increments within typical flow ranges for each cannula. Pre-cannula and post-cannula pressures were measured to calculate the pressure drop. Results: Utilizing a pressure drop limit of 100 mmHg, our results suggest a recommended flow limit of 500, 900, 1400, 2600, and 3100 mL/min for Braile arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, respectively. For Medtronic DLP arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, the recommended flow limit is 600, 1100, 1700, 2700, and 3300 mL/min, respectively. Conclusion: This study reinforces discrepancies in pressure drop between cannulae of the same diameter supplied by different manufacturers and the importance of independent translational research to evaluate components' performance.

A Multi-objective Physiological Control for Continuous Flow Left Ventricular Assist Devices: Comparison of Estimator versus Sensor-based Feedback.

Left Ventricular Assist Devices have been successfully used for the treatment of Congestive Heart failure in patients who are not eligible for heart transplantation. This paper describes the implementation and comparison of the performance of a pressure sensor-based feedback controller. The strategies were tested on a mock loop of the systemic circulation. The results show that the use of pressure sensors generated a more accurate response of the controller compared to the use of estimators.Clinical Relevance- The study describes the integration of a LVAD physiological controller to a dynamic wireless monitoring system.

Performance Evaluation of Geometrically Different Pediatric Arterial Cannulae in a Pediatric Cardiopulmonary Bypass Model.

OBJECTIVE: To define a reference chart comparing pressure drop vs. flow generated by a set of arterial cannulae currently utilized in cardiopulmonary bypass conditions in pediatric surgery. METHODS: Cannulae from two manufacturers were selected considering their design and outer and inner diameters. Cannula performance was evaluated in terms of pressure drop vs. flow during simulated cardiopulmonary bypass conditions. The experimental circuits consisted of a Jostra HL-20 roller pump, a Quadrox-i pediatric oxygenator (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set. The circuit was primed with lactated Ringer's solution only (first condition) and with human packed red blood cells added (second condition) to achieve a hematocrit of 30%. Cannula sizes 8 to 16 Fr were inserted into the cardiopulmonary bypass circuit with a "Y" connector. The flow was adjusted in 100 ml/min increments within typical flow ranges for each cannula. Pre-cannula and post-cannula pressures were measured to calculate the pressure drop. RESULTS: Utilizing a pressure drop limit of 100 mmHg, our results suggest a recommended flow limit of 500, 900, 1400, 2600, and 3100 mL/min for Braile arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, respectively. For Medtronic DLP arterial cannulae sizes 8, 10, 12, 14, and 16 Fr, the recommended flow limit is 600, 1100, 1700, 2700, and 3300 mL/min, respectively. CONCLUSION: This study reinforces discrepancies in pressure drop between cannulae of the same diameter supplied by different manufacturers and the importance of independent translational research to evaluate components' performance.

Safety of an esophageal deviator for atrial fibrillation catheter ablation.

Background: Esophageal thermal injury is a complication of atrial fibrillation (AF) ablation, and it can be avoided by esophageal deviation during left atrial posterior wall radiofrequency catheter ablation. Objective: This study aimed to evaluate the safety of a nitinol-based mechanical esophageal displacement device (MEDD) and its performance. Methods: This preclinical safety study was conducted on 20 pigs, with 10 undergoing radiofrequency AF ablation using the MEDD and 10 serving as a control group under anticoagulation but without radiofrequency application. Esophageal traumatic injuries were classified from 0 to 4 and were grouped as absent (grade 0), minor (grade 1 or 2), moderate (grade 3), or major risk lesions (grade 4) by anatomopathological study. Grades 1 and 2 were considered acceptable. Fluoroscopy was used to measure displacement. Results: Five (25%) pigs developed traumatic lesions, 4 with grade 1 and 1 with grade 2 (2-mm superficial ulcer). There was no difference in lesion occurrence between the radiofrequency and control groups (30% and 20%, respectively; P = .43). Under rightward displacement, the right edge moved 23.9 (interquartile range [IQR] 21.3-26.3) mm and the left edge moved 16.3 (IQR 13.8-18.4) mm (P < .001) from baseline. Under leftward displacement, the right edge moved 13.5 (IQR 10.9-15.3) mm and the left edge moved 16.5 (IQR 12.3-18.5) mm (P = .07). A perforation to the pharyngeal diverticulum occurred in 1 pig, related to an accidental extubation. Conclusion: In pigs, the MEDD demonstrated safety in relation to esophageal tissue, and successful deviation. Esophageal traumatic injuries were acceptable, but improper manipulation led to pharyngeal lesion.

Evaluation of Structural Viability of Porcine Tracheal Scaffolds after 3 and 6 Months of Storage under Three Different Protocols.

Tracheal replacement with a bioengineered tracheal substitute has been developed for long-segment tracheal diseases. The decellularized tracheal scaffold is an alternative for cell seeding. It is not defined if the storage scaffold produces changes in the scaffold's biomechanical properties. We tested three protocols for porcine tracheal scaffold preservation immersed in PBS and alcohol 70%, in the fridge and under cryopreservation. Ninety-six porcine tracheas (12 in natura, 84 decellularized) were divided into three groups (PBS, alcohol, and cryopreservation). Twelve tracheas were analyzed after three and six months. The assessment included residual DNA, cytotoxicity, collagen contents, and mechanical properties. Decellularization increased the maximum load and stress in the longitudinal axis and decreased the maximum load in the transverse axis. The decellularization of the porcine trachea produced structurally viable scaffolds, with a preserved collagen matrix suitable for further bioengineering. Despite the cyclic washings, the scaffolds remained cytotoxic. The comparison of the storage protocols (PBS at 4 °C, alcohol at 4 °C, and slow cooling cryopreservation with cryoprotectants) showed no significant differences in the amount of collagen and in the biomechanical properties of the scaffolds. Storage in PBS solution at 4 °C for six months did not change the scaffold mechanics.

The Distensibility of the Human Vena Cava and Its Importance to In Vitro Studies of Venous Compression Syndromes: A Search for a Suitable Polymer for 3-Dimensional Printing.

BACKGROUND: Venous compression syndromes are clinical conditions in which the large veins are compressed by other anatomical structures. Laboratory simulations may help us better understand the hemodynamics in venous compressions by creating situations similar to those seen in vivo. The aim of this study is to produce a model of the caval bifurcation using a polymer with distensibility similar to the human vena cava. METHODS: Fragments of the inferior vena cava were collected from 13 deceased kidney donors (aged 15-37 years) and were tested for deformation (strain) when subjected to distension at 50 N/cm2. Strips of 5 different polymers-thermic polyurethane and Agilus30 with Vero Magenta (AV) (in 3 different hardnesses) and silicone-were subjected to the same biomechanical tests and compared with the vena cava. A model of the caval bifurcation was produced with 3-D printing. RESULTS: The deformation (strain) of the vena cava wall was 0.16 ± 0.9 when submitted to stress close to 50 N/cm2. Silicone showed a strain higher than the standard deviation of venous fragments. The strain of AV resin 95 Shore was lower than the standard deviation of the venous fragments. AV Resins 70 and 85 Shore showed strains within the standard deviation of the venous specimen, with 70 Shore being closest to the mean venous strain. Therefore, this material was selected for modeling the caval bifurcation. The computed tomography scan image generated a computer model of the caval bifurcation and was printed in 3 dimensions. In addition, the segments of 2 adjacent vertebrae were also printed to reference the compression site. CONCLUSIONS: The 3-D printing of large veins can produce models with anatomy and biomechanics similar to those of human veins and opens a field of investigation into the hemodynamics of venous compression syndromes. Polymers with Shore A70 appear to have biomechanical properties similar to those of the vena cava wall. The model obtained in this study can be used in several in vitro studies of May-Thurner Syndrome.

Effect of the bileaflet inlet valve angle on the flow of a pediatric ventricular assist device: Experimental analysis.

BACKGROUND: Mechanical heart valves (MHV) and its fluid dynamics inside a pulsatile pediatric ventricular assist device (PVAD) can be associated with blood degradation. In this article, flow structures are analyzed and compared by an experimental investigation on the effect of bileaflet MHV positioned at varying angles in the inlet port orifice of a PVAD. METHODS: Time-resolved particle image velocimetry was applied to characterize the internal flow of the device. St Jude Medical bileaftlet valves were used on the inlet orifice and positioned at 0°, 15°, 30°, 45°, 60°, and 90° in relation to the centerline of the device. Three planes with bidimensional velocity magnitude fields were considered in the analysis with visualization of diastolic jets, device wall washing patterns and flow circulation during emptying or systole of the pump. Also, the washing vortex area, and vertical velocity probabilities of regurgitant flows in the inlet valve were evaluated. RESULTS: The results show that a variation in the angle of the MHV at the inlet port produced distinct velocities, fluid structures, and regurgitant flow probabilities within the device. MHV positioned at an angle of 0° generated the strongest inlet jet, larger vortex area during filling, more prominent outgoing flow, and less regurgitation compared to the angles studied. The presence of unfavorable fluid structures, such as small vortices, and/or sudden flow structure interruption, and/or regurgitation, were identified at 45° and 90° angles. CONCLUSIONS: The 0° inlet angle had better outcomes than other angles due to its consistency in the multiple parameters analyzed.

Tissue Engineering and Cell Therapy for Cartilage Repair: Preclinical Evaluation Methods.

A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSCs), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts, are a predictable source for the treatment of cartilage injuries. This article presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and preclinical large animal model. In this controlled experimental study with 14 miniature pigs, a scaffold-free tissue engineering construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging (MRI) using the three-dimensional double echo steady-state (3D-DESS) sequence, and compositional assessment was carried out based on the T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, subjected to standard histological processing, sectioned, and stained with hematoxylin and eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of Young's modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a finite element model was used to simulate and characterize properties of the osteochondral block. At 6 months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical, and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after 6 months of follow-up in a large animal model for articular cartilage restoration. Impact Statement Articular chondral injuries are prevalent and represent an economic burden due to the cost of treatment. The engineering of cartilage tissue can promote the repair of chondral injuries and is dependent on selecting appropriate cells and biocompatible frameworks. In this article, methods for evaluation of a scaffold-free cell delivery system made from mesenchymal stromal cells were present in a translational study that allows further clinical safety and efficacy trials.

Blood cell adhesion to arterial filters analysis by scanning electron microscopy and real-time PCR assay: observational clinical study in cardiac surgery patients.

INTRODUCTION: Arterial filter is the part of the cardiopulmonary bypass circuit where blood cells are exposed to high mechanical stress and where cellular aggregates may fasten in large quantities. The aim of this study was to analyse blood cell adhesiveness in the arterial filter through scanning electron microscopy and real-time PCR assay. METHODS: Prospective, clinical and observational study performed on 28 patients undergoing cardiac surgery with cardiopulmonary bypass. Arterial filters were analysed by scanning electron microscopy. Real-time PCR assay was performed in extracted material from the arterial filters for analysis of platelet GPIb and CD45 leucocyte gene expression. Blood coagulation was analysed during cardiopulmonary bypass. Patients were followed until hospital discharge or 28 days after surgery. RESULTS: All studied arterial filters used in the subject patients showed a degree of adhesion from blood elements at scanning electron microscopy. All studied filters were positive for platelets GPIb gene expression and 15% had CD45 leucocyte gene expression. The GPIb platelet gene expression in blood lowered at the end of cardiopulmonary bypass (p = 0.019). There was negative correlation between blood GPIb platelet gene expression and Clot SR (HEPSCREEN2 ReoRox®) (rho = 0.635; p = 0.027). The filter fields count was correlated to the D-dimer dosage (rho = 0.828; p < 0.001). CONCLUSION: There was adhesion of blood elements, especially nucleated platelets, on all arterial filters studied. Although the arterial filter worked as a safety device, that possibly prevented arterial embolisation, it may also have caused greater hyperfibrinolysis during cardiopulmonary bypass.

Protótipo de cateter vesical de três vias para a Lavagem Vesical / Three-way bladder catheter prototype for bladder washing

As principais complicações pós-operatórias de Ressecção Transuretral da Próstata (RTU-P) são: retenção urinária por coágulos sanguíneos na sonda e a contaminação exógena do sistema urinário por manipulação do profissional de saúde ao realizar a técnica de lavagem vesical. O artigo descreve o desenvolvimento de um protótipo para a manutenção do sistema urinário fechado durante a lavagem vesical e permitir a medição das pressões no interior do cateter vesical de demora (CVD) de três vias com o protótipo durante a técnica da lavagem vesical. Trata-se de uma pesquisa tecnológica baseada no modelo de Processo de Desenvolvimento do Produto de Rozenfeld. Foram realizados testes de funcionalidade por meio de experimentos em ambiente controlado dentro de laboratório. O protótipo apresentou resultados satisfatórios quanto a manutenção do sistema urinário fechado durante a técnica de lavagem vesical. O uso do catéter permitiu a medição das pressões específicas do CVD de três vias em três momentos diferentes: cateter desobstruído, cateter parcialmente obstruído e cateter totalmente obstruído. Os resultados obtidos demonstram que o protótipo pode representar uma ferramenta inovadora na área de urologia. Atendeu as especificações do projeto e possibilitou a manutenção do sistema urinário fechado na lavagem vesical. Além de diminuir os riscos de contaminação do sistema urinário durante a manipulação da técnica. Portanto, o presente estudo demostrou que o protótipo é plenamente seguro quando comparado as pressões exercidas dentro do CVD. Existe a necessidade de realizar testes experimentais em humanos para comprovar a diminuição de contaminação do trato urinário como uso do protótipo.

The main postoperative complications of Transurethral Resection of the Prostate (TURP) are urinary retention by blood clots in the probe and exogenous contamination of the urinary system by manipulation of the healthcare professional when performing the bladder washing technique. The aim of this study was to develop a prototype for keeping the urinary system closed during bladder washes and to measure the internal pressures of the three-way Indwelling Urinary Catheter (IDC) during the bladder washing technique. This was a technological study based on the Rozenfeld's Product Development Process model. Functionality tests were carried out through experiments in a controlled environment in the laboratory. The prototype showed satisfactory results regarding the preservation of the urinary system closed during the bladder washing technique. It was possible to obtain specific pressures from the three-way IDC at three different moments: unobstructed catheter, partially obstructed catheter, and totally obstructed catheter. The results obtained demonstrate that the prototype can represent an innovative tool in the area of urology. It met the project's specifications and preserved the urinary system closed during the bladder washing. Moreover, it reduces the risk of urinary system contamination during the technique manipulation. Therefore, the present study showed that the prototype is fully safe regarding the pressures exerted inside the IDC. There is a need to carry out experimental tests in humans to prove the decrease of urinary tract contamination with the use of this prototype.

Conditioning of hiPSC-derived cardiomyocytes using surface topography obtained with high throughput technology.

Surface functionalization of polymers aims to introduce novel properties that favor bioactive responses. We have investigated the possibility of surface functionalization of polyethylene terephthalate (PET) sheets by the combination of laser ablation with hot embossing and the application of such techniques in the field of stem cell research. We investigated the response of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to topography in the low micrometer range. HiPSC-CMs are expected to offer new therapeutic tools for myocardial replacement or regeneration after an infarct or other causes of cardiac tissue loss. However, hiPSC-CMs are phenotypically immature compared to myocytes in the adult myocardium, hampering their clinical application. We aimed to develop and test a high-throughput technique for surface structuring that would improve hiPSC-CMs structural maturation. We used laser ablation with a ps-laser source in combination with nanoimprint lithography to fabricate large areas of homogeneous micron- to submicron line-like pattern with a spatial period of 3 µm on the PET surface. We evaluated cell morphology, alignment, sarcomeric myofibrils assembly, and calcium transients to evaluate phenotypic changes associated with culturing hiPSC-CMs on functionalized PET. Surface functionalization through hot embossing was able to generate, at low cost, low micrometer features on the PET surface that influenced the hiPSC-CMs phenotype, suggesting improved structural and functional maturation. This technique may be relevant for high-throughput technologies that require conditioning of hiPSC-CMs and may be useful for the production of these cells for drug screening and disease modeling applications with lower costs.

Early changes in myocyte contractility and cardiac function in streptozotocin-induced type 1 diabetes in rats.

Diabetes can elicit direct deleterious effects on the myocardium, independent of coronary artery disease or hypertension. These cardiac disturbances are termed diabetic cardiomyopathy showing increased risk of heart failure with or without reduced ejection fraction. Presently, there is no specific treatment for this type of cardiomyopathy and in the case of type I diabetes, it may start in early childhood independent of glycemic control. We hypothesized that alterations in isolated myocyte contractility and cardiac function are present in the early stages of experimental diabetes in rats before overt changes in myocardium structure occur. Diabetes was induced by single-dose injection of streptozotocin (STZ) in rats with data collected from control and diabetic animals 3 weeks after injection. Left ventricle myocyte contractility was measured by single-cell length variation under electrical stimulation. Cardiac function and morphology were studied by high-resolution echocardiography with pulsed-wave tissue Doppler imaging (TDI) measurements and three-lead surface electrocardiogram. Triglycerides, cholesterol and liver enzyme levels were measured from plasma samples obtained from both groups. Myocardial collagen content and perivascular fibrosis of atria and ventricle were studied by histological analysis after picrosirius red staining. Diabetes resulted in altered contractility of isolated cardiac myocytes with increased contraction and relaxation time intervals. Echocardiography showed left atrium dilation, increased end-diastolic LV and posterior wall thickness, with reduced longitudinal systolic peak velocity (S') of the septum mitral annulus at the apical four-chamber view obtained by TDI. Triglycerides, aspartate aminotransferase and alkaline phosphatase were elevated in diabetic animals. Intertitial collagen content was higher in atria of both groups and did not differ among control and diabetic animals. Perivascular intramyocardial arterioles collagen did not differ between groups. These results suggest that alterations in cardiac function are present in the early phase in this model of diabetes type 1 and occur before overt changes in myocardium structure appear as evaluated by intersticial collagen deposition and perivascular fibrosis of intramyocardial arterioles.

Impact of Vacuum-Assisted Venous Drainage on Forward Flow in Simulated Pediatric Cardiopulmonary Bypass Circuits Utilizing a Centrifugal Arterial Pump Head.

OBJECTIVE: To analyze the impact of vacuum-assisted venous drainage (VAVD) on arterial pump flow in a simulated pediatric cardiopulmonary bypass circuit utilizing a centrifugal pump (CP) with an external arterial filter. METHODS: The simulation circuit consisted of a Quadrox-I Pediatric oxygenator, a Rotaflow CP (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set primed with Lactated Ringer's solution and packed red blood cells. Venous line pressure, reservoir pressure, and arterial flow were measured with VAVD turned off to record baseline values. Four other conditions were tested with progressively higher vacuum pressures (-20, -40, -60, and -80 mmHg) applied to the baseline cardiotomy pressure. An arterial filter was placed into the circuit and arterial flow was measured with the purge line in both open and closed positions. These trials were repeated at set arterial flow rates of 1500, 2000, and 2500 mL/min. RESULTS: The use of progressively higher vacuum caused a reduction in effective arterial flow from 1490±0.00 to 590±0.00, from 2020±0.01 to 1220±0.00, and from 2490±0.0 to 1830±0.01 mL/min. Effective forward flow decreased with increased levels of VAVD. CONCLUSION: The use of VAVD reduces arterial flow when a CP is used as the main arterial pump. The reduction in the forward arterial flow increases as the vacuum level increases. The loss of forward flow is further reduced when the arterial filter purge line is kept in the recommended open position.An independent flow probe is essential to monitor pump flow during cardiopulmonary bypass.

Comparative study of strategies to prevent esophageal and periesophageal injury during atrial fibrillation ablation.

OBJECTIVE: To compare the prevalence of esophageal and periesophageal thermal injury in patients undergoing radiofrequency (RF) atrial fibrillation (AF) ablation using 8 mm tip catheters during three different esophageal protection strategies. METHODS: Forty-five consecutive patients with paroxysmal or persistent AF underwent first ablation procedure, besides esophagogastroduodenoscopy (EGD) combined with radial endosonography (EUS) performed before and after the pulmonary vein (PV) isolation. Before the procedure, patients were randomly assigned to one of three esophageal lesion protection strategies: group I-without any protective or monitoring dispositive and limiting RF applications to 30 W for 20 seconds, in left atrium posterior wall (LAPW); group II-power and time of RF delivery, up to 50 W for 20 seconds at LAPW, limited by esophageal temperature monitoring; group III-applications of RF in LAPW with fixed power application of 50 W for 20 seconds during continuous esophageal cooling. RESULTS: Baseline characteristics of patients were similar in all groups. The four PVs were isolated in 14 (93.3%), 13 (86.7%), and 15 (100%) patients, respectively in groups I, II, and III. The mean RF power was significantly higher (P < .001) in the posterior side of PVs in group III. Post-AF ablation EGD and EUS revealed two esophageal wall ulcerations and two periesophageal mediastinal edemas only in the esophageal cooling group (P = .008). CONCLUSION: Esophageal cooling balloon strategy resulted in a higher RF power energy delivery when ablating at the LA posterior wall, using 8 mm nonirrigated tip catheters under temperature mode control. Despite that, patients presented a relatively low incidence of esophageal and periesophaeal injuries.

Impact of vacuum-assisted venous drainage on forward flow in simulated pediatric cardiopulmonary bypass circuits utilizing a centrifugal arterial pump head

Abstract Objective: To analyze the impact of vacuum-assisted venous drainage (VAVD) on arterial pump flow in a simulated pediatric cardiopulmonary bypass circuit utilizing a centrifugal pump (CP) with an external arterial filter. Methods: The simulation circuit consisted of a Quadrox-I Pediatric oxygenator, a Rotaflow CP (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set primed with Lactated Ringer's solution and packed red blood cells. Venous line pressure, reservoir pressure, and arterial flow were measured with VAVD turned off to record baseline values. Four other conditions were tested with progressively higher vacuum pressures (-20, -40, -60, and -80 mmHg) applied to the baseline cardiotomy pressure. An arterial filter was placed into the circuit and arterial flow was measured with the purge line in both open and closed positions. These trials were repeated at set arterial flow rates of 1500, 2000, and 2500 mL/min. Results: The use of progressively higher vacuum caused a reduction in effective arterial flow from 1490±0.00 to 590±0.00, from 2020±0.01 to 1220±0.00, and from 2490±0.0 to 1830±0.01 mL/min. Effective forward flow decreased with increased levels of VAVD. Conclusion: The use of VAVD reduces arterial flow when a CP is used as the main arterial pump. The reduction in the forward arterial flow increases as the vacuum level increases. The loss of forward flow is further reduced when the arterial filter purge line is kept in the recommended open position. An independent flow probe is essential to monitor pump flow during cardiopulmonary bypass.

Characterization of a pediatric rotary blood pump

Abstract Introduction A ventricular assist device (VAD) is an electromechanical pump used to treat heart failures. For designing the physiological control system for a VAD, one needs a mathematical model and its related parameters. This paper presents a characterization procedure for determining the model parameter values of the electrical, mechanical, and hydraulic subsystems of a pediatric Rotary Blood Pump (pRBP). Methods An in vitro test setup consisting of a pRBP prototype, a motor driver module, an acrylic reservoir, mechanical resistance and tubings, pressure and fluid flow sensors, and data acquisition, processing, and visualization system. The proposed procedure requires a set of experimental tests, and a parameter estimation algorithm for determining the model parameters values. Results The operating limits of the pRBP were identified from the steady-state data. The relationship between the pressure head, flow rate, and the rotational speed of the pRBP was found from the static tests. For the electrical and mechanical subsystems, the dc motor model has a viscous friction coefficient that varies nonlinearly with the flow. For the hydraulic subsystem, the pressure head is assumed to be a sum of terms related to the resistance, the inertance, the friction coefficient, and the pump speed. Conclusion The proposed methodology was successfully applied to the characterization of the pRBP. The combined use of static and dynamic tests provided a precise lumped parameter model for representing the pRBP dynamics. The agreement, regarding mean squared deviation, between experimental and simulated results demonstrates the correctness and feasibility of the characterization procedure.

Functional Performance of Different Venous Limb Options in Simulated Neonatal/Pediatric Cardiopulmonary Bypass Circuits.

OBJECTIVE: Hemodilution is a concern in cardiopulmonary bypass (CPB). Using a smaller dual tubing rather than a single larger inner diameter (ID) tubing in the venous limb to decrease prime volume has been a standard practice. The purpose of this study is to evaluate these tubing options. METHODS: Four different CPB circuits primed with blood (hematocrit 30%) were investigated. Two setups were used with two circuits for each one. In Setup I, a neonatal oxygenator was connected to dual 3/16" ID venous limbs (Circuit A) or to a single 1/4" ID venous limb (Circuit B); and in Setup II, a pediatric oxygenator was connected to dual 1/4" ID venous limbs (Circuit C) or a single 3/8" ID venous limb (Circuit D). Trials were conducted at arterial flow rates of 500 ml/min up to 1500 ml/min (Setup I) and up to 3000 ml/min (Setup II), at 36°C and 28°C. RESULTS: Circuit B exhibited a higher venous flow rate than Circuit A, and Circuit D exhibited a higher venous flow rate than Circuit C, at both temperatures. Flow resistance was significantly higher in Circuits A and C than in Circuits B (P<0.001) and D (P<0.001), respectively. CONCLUSION: A single 1/4" venous limb is better than dual 3/16" venous limbs at all flow rates, up to 1500 ml/min. Moreover, a single 3/8" venous limb is better than dual 1/4" venous limbs, up to 3000 ml/min. Our findings strongly suggest a revision of perfusion practice to include single venous limb circuits for CPB.

Functional performance of different venous limb options in simulated neonatal/pediatric cardiopulmonary bypass circuits

Abstract Objective: Hemodilution is a concern in cardiopulmonary bypass (CPB). Using a smaller dual tubing rather than a single larger inner diameter (ID) tubing in the venous limb to decrease prime volume has been a standard practice. The purpose of this study is to evaluate these tubing options. Methods: Four different CPB circuits primed with blood (hematocrit 30%) were investigated. Two setups were used with two circuits for each one. In Setup I, a neonatal oxygenator was connected to dual 3/16" ID venous limbs (Circuit A) or to a single 1/4" ID venous limb (Circuit B); and in Setup II, a pediatric oxygenator was connected to dual 1/4" ID venous limbs (Circuit C) or a single 3/8" ID venous limb (Circuit D). Trials were conducted at arterial flow rates of 500 ml/min up to 1500 ml/min (Setup I) and up to 3000 ml/min (Setup II), at 36°C and 28°C. Results: Circuit B exhibited a higher venous flow rate than Circuit A, and Circuit D exhibited a higher venous flow rate than Circuit C, at both temperatures. Flow resistance was significantly higher in Circuits A and C than in Circuits B (P<0.001) and D (P<0.001), respectively. Conclusion: A single 1/4" venous limb is better than dual 3/16" venous limbs at all flow rates, up to 1500 ml/min. Moreover, a single 3/8" venous limb is better than dual 1/4" venous limbs, up to 3000 ml/min. Our findings strongly suggest a revision of perfusion practice to include single venous limb circuits for CPB.

Integrated molecular, biochemical, and physiological assessment unravels key extraction method mediated influences on rat neonatal cardiomyocytes.

Neonatal cardiomyocytes are instrumental for disease modeling, but the effects of different cell extraction methods on basic cell biological processes remain poorly understood. We assessed the influence of two popular methods to extract rat neonatal cardiomyocytes, Pre-plating (PP), and Percoll (PC) on cell structure, metabolism, and function. Cardiomyocytes obtained from PP showed higher gene expression for troponins, titin, and potassium and sodium channels compared to PC. Also, PP cells displayed higher levels of troponin I protein. Cells obtained from PC displayed higher lactate dehydrogenase activity and lactate production than PP cells, indicating higher anaerobic metabolism after 8 days of culture. In contrast, reactive oxygen species levels were higher in PP cells as indicated by ethidium and hydroxyethidium production. Consistent with these data, protein nitration was higher in PP cells, as well as nitrite accumulation in cell medium. Moreover, PP cells showed higher global intracellular calcium under basal and 1 mM isoprenaline conditions. In a calcium-transient assessment under electrical stimulation (0.5 Hz), PP cells displayed higher calcium amplitude than cardiomyocytes obtained from PC and using a traction force microscope technique we observed that PP cardiomyocytes showed the highest relaxation. Collectively, we demonstrated that extraction methods influence parameters related to cell structure, metabolism, and function. Overall, PP derived cells are more active and mature than PC cells, displaying higher contractile function and generating more reactive oxygen species. On the other hand, PC derived cells display higher anaerobic metabolism, despite comparable high yields from both protocols.

In Vitro Evaluation of Pediatric Hollow-Fiber Membrane Oxygenators on Hemodynamic Performance and Gaseous Microemboli Handling: An International Multicenter/Multidisciplinary Approach.

The objective of this study was to compare the hemodynamic performances and gaseous microemboli (GME) handling ability of two pediatric oxygenators in a simulated pediatric cardiopulmonary bypass (CPB) model and the importance of adding an arterial filter in the circuit. The circuit consisted of a Braile Infant oxygenator or a Maquet Quadrox-I Pediatric oxygenator without integrated arterial filter (parallel arrangement), 1/4 in. ID tubing A-V loop, and a 12-Fr arterial cannula, primed with lactated Ringer's solution and packed red blood cells. Trials were conducted at flow rates ranging from 500 to 2000 mL/min (500 mL/min increment) at 35°C and 28°C. Real-time pressure and flow data were recorded using a custom-based data acquisition system. For GME testing, 5 cc of air was manually injected into the venous line. GME were recorded using the Emboli Detection and Classification Quantifier (EDAC) System. An additional experiment using a separate arterial filter was conducted. There was no difference in the mean circuit pressure, pressure drop, total hemodynamic energy level, and energy loss between the two oxygenators. The venous line pressures were higher in the Braile than in the Quadrox group during all trials (P <0.01). GME count and volume at pre-/post oxygenator and pre-cannula sites in the Quadrox were lower than the Braile group at high flow rates (P < 0.05). In the additional experiment, an arterial filter captured a significant number of microemboli at all flow rates. The Braile Infant oxygenator has a matched hemodynamic characteristic with the Quadrox-i Pediatric oxygenator. The Quadrox-i has a better GME handling ability compared with the Braile Infant oxygenator. Regardless of type of oxygenator an additional arterial filter decreases the number of GME.