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Background: A critical parameter of extracorporeal CO2 removal (ECCO2R) applications is the CO2 removal rate (VCO2). Low‐flow venovenous extracorporeal support with large‐size membrane lung remains undefined. This study aimed to evaluate the VCO2 of a low‐flow ECCO2R with large‐size membrane lung using a renal replacement therapy platform in an experimental animal model. Methods: Twelve healthy pigs were placed under mechanical ventilation and connected to an ECCO2R‐CRRT system (surface area = 1.8 m2; OMNIset®, BBraun, Germany). Respiratory settings were reduced to induce two degrees of hypercapnia. VCO2 was recorded under different combinations of PaCO2 (50–69 or 70–89 mm Hg), extracorporeal blood flow (ECBF; 200 or 350 mL/min), and gas flow (4, 6, or 10 L/min). Results: VCO2 increased with ECBF at all three gas flow rates. In severe hypercapnia, the increase in sweep gas flow from 4 to 10 L/min increased VCO2 from 86.38 ± 7.08 to 96.50 ± 8.71 mL/min at an ECBF of 350 mL/min, whereas at ECBF of 200 mL/min, any increase was less effective. But in mild hypercapnia, the increase in sweep gas flow result in significantly increased VCO2 at two ECBF. VCO2 increased with PaCO2 from 50–69 to 70–89 mm Hg at an ECBF of 350 mL/min, but not at ECBF of 200 mL/min. Post‐membrane lung PCO2 levels were similar for different levels of premembrane lung PCO2 (p = 0.08), highlighting the gas exchange diffusion efficacy of the membrane lung in gas exchange diffusion. In severe hypercapnia, the reduction of PaCO2 elevated from 11.5% to 19.6% with ECBF increase only at a high gas flow of 10 L/min (p < 0.05) and increase of gas flow significantly reduced PaCO2 only at a high ECBF of 350 mL/min (p < 0.05). Conclusions: Low‐flow venovenous extracorporeal ECCO2R‐CRRT with large‐size membrane lung is more efficient with the increase of ECBF, sweep gas flow rate, and the degree of hypercapnia. The influence of sweep gas flow on VCO2 depends on the ECBF and degree of hypercapnia. Higher ECBF and gas flow should be chosen to reverse severe hypercapnia. [ABSTRACT FROM AUTHOR]

Heart valves serve a vital hemodynamic function to ensure unidirectional blood flow. Additionally, native heart valves serve biological functions such as growth and self‐repair. Heart valve implants mimic the hemodynamic function of native heart valves, but are unable to fulfill their biological functions. We developed partial heart transplantation to deliver heart valve implants that fulfill all functions of native heart valves. This is particularly advantageous for children, who require growing heart valve implants. This invited review outlines the past, present and future of partial heart transplantation. [ABSTRACT FROM AUTHOR]

Background: Silicon nanopore membrane‐based implantable bioartificial organs are dependent on arteriovenous implantation of a mechanically robust and biocompatible hemofilter. The hemofilter acts as a low‐resistance, high‐flow network, with blood flow physiology similar to arteriovenous shunts commonly created for hemodialysis access. A mock circulatory loop (MCL) that mimics shunt physiology is an essential tool for refinement and durability testing of arteriovenous implantable bioartificial organs and silicon blood‐interfacing membranes. We sought to develop a compact and cost‐effective MCL to replicate flow conditions through an arteriovenous shunt and used data from the MCL and swine to inform a bond graph mathematical model of the physical setup. Methods: Flow physiology through bioartificial organ prototypes was obtained in the MCL and during extracorporeal attachment to swine for biologic comparison. The MCL was tested for stability overtime by measuring pressurewave variability over a 48‐h period. Data obtained in vitro and extracorporeally informed creation of a bond graph model of the MCL. Results: The arteriovenous MCL was a cost‐effective, portable system that reproduced flow rates and pressures consistent with a pulsatile arteriovenous shunt as measured in swine. MCL performance was stable over prolonged use, providing a cost‐effective simulator for enhanced testing of peripherally implanted bioartificial organ prototypes. The corresponding bond graph model recapitulates MCL and animal physiology, offering a tool for further refinement of the MCL system. [ABSTRACT FROM AUTHOR]

Background: Validated quantitative biomarkers for assessment of renal graft function during normothermic machine perfusion (NMP) conditions are lacking. The aim of this project was to quantify cortex microperfusion during ex vivo kidney perfusion using laser speckle contrast imaging (LSCI), and to evaluate the sensitivity of LSCI when measuring different levels of renal perfusion. Furthermore, we aimed to introduce LSCI measurements during NMP in differentially damaged kidneys. Methods: Eleven porcine kidneys were nephrectomized and perfused ex vivo. Cortex microperfusion was simultaneously monitored using LSCI. First, a flow experiment examined the relationship between changes in delivered renal flow and corresponding changes in LSCI‐derived cortex microperfusion. Second, renal cortical perfusion was reduced stepwise by introducing a microembolization model. Finally, LSCI was applied for measuring renal cortex microperfusion in kidneys exposed to minimal damage or 2 h warm ischemia (WI). Results: Cortex microperfusion was calculated from the LSCI‐obtained data. The flow experiment resulted in relatively minor changes in cortex microperfusion compared to the pump‐induced changes in total renal flow. Based on stepwise injections of microspheres, we observed different levels of cortex microperfusion that correlated with administrated microsphere dosages (r2 = 0.95–0.99). We found no difference in LSCI measured cortex microperfusion between the kidneys exposed to minimal damage (renal cortex blood flow index, rcBFI = 2090–2600) and 2 h WI (rcBFI = 2189–2540). Conclusions: Based on this preliminary study, we demonstrated the feasibility of LSCI in quantifying cortex microperfusion during ex vivo perfusion. Furthermore, based on LSCI‐measurements, cortical microperfusion was similar in kidneys exposed to minimal and 2 h WI. [ABSTRACT FROM AUTHOR]

Background: ModulHeart (Puzzle Medical Devices Inc) is a novel percutaneous flow entrainment pump anchored in the descending aorta. The current study evaluates the hemodynamic effect of ModulHeart support and its impact on cerebral, myocardial, and renal blood flow. Methods: ModulHeart was implanted in the descending aorta of four healthy calves. A ramp protocol (2000 RPM increments) was performed with the pump operating at five different speeds from 14 000 to 22 000 RPM. For each speed, pressures proximal and distal to the pump, and right heart catheterization measurements were recorded. Stable‐isotope labeled microspheres were injected in the left ventricle to evaluate organ perfusion. Results: Thermodilution cardiac output increased by 23% at 22 000 RPM. Greater pump speeds resulted in greater pump gradients, up to 10 mm Hg in mean arterial pressure at 22 000 RPM, without significant reduction of proximal perfusion pressures. Arterial pulse pressure remained stable at all speeds. ModulHeart was not associated with a reduction in cerebral or myocardial blood flow at any speed. Renal cortical and medullary blood flow increased by up to 50% and 40%, respectively. Conclusion: The ModulHeart device implanted in the descending aorta of healthy calves resulted in significant arterial pressure gradients and preserved pulse pressure. Greater pump speeds translated into greater increases in renal blood flow, with no decrease in cerebral or myocardial perfusion. [ABSTRACT FROM AUTHOR]

Background: Abdominal normothermic regional perfusion (A‐NRP) allows in‐situ reperfusion and recovery of abdominal organs metabolism in donors after circulatory death (DCD). Besides improving liver transplantation outcomes, liver injury and function can be assessed during A‐NRP. Methods: To refine liver viability assessment during A‐NRP, prospectively collected data of controlled DCD donors managed at our Institution between October 2019 and May 2022 were retrospectively analyzed. Baseline characteristics, procedural variables and A‐NRP parameters of donors whose liver was successfully transplanted were compared to those of donors whose liver was discarded. Results: Twenty‐seven donors were included and in 20 (74%) the liver was accepted (positive outcome). No differences between study groups were observed concerning baseline characteristics and warm ischemia times (WIT). Initial lactate levels were positively correlated with functional WIT (r2 = 0.4, p = 0.04), whereas transaminase levels were not. Blood flow during A‐NRP was comparable, whereas oxygen consumption (VO2) was significantly higher in the positive outcome group after 1 h. Time courses of lactate, AST and ALT were significantly different between study groups (p < 0.001). Donors whose liver was accepted showed faster lactate clearance, a difference which was amplified by normalizing lactate clearance to oxygen delivery (DO2) and VO2. Lactate clearance was correlated to transaminase levels and DO2‐normalized lactate clearance was the parameter best discriminating between study groups. Conclusions: DO2‐normalized lactate clearance may represent an element of liver viability assessment during A‐NRP. [ABSTRACT FROM AUTHOR]

Background: Extracorporeal organ assist devices provide lifesaving functions for acutely and chronically ill patients suffering from respiratory and renal failure, but their availability and use is severely limited by an extremely high level of operational complexity. While current hollow fiber‐based devices provide high‐efficiency blood gas transfer and waste removal in extracorporeal membrane oxygenation (ECMO) and hemodialysis, respectively, their impact on blood health is often highly deleterious and difficult to control. Further challenges are encountered when integrating multiple organ support functions, as is often required when ECMO and ultrafiltration (UF) are combined to deal with fluid overload in critically ill patients, necessitating an unwieldy circuit containing two separate cartridges. Methods: We report the first laboratory demonstration of simultaneous blood gas oxygenation and fluid removal in single microfluidic circuit, an achievement enabled by the microchannel‐based blood flow configuration of the device. Porcine blood is flowed through a stack of two microfluidic layers, one with a non‐porous, gas‐permeable silicone membrane separating blood and oxygen chambers, and the other containing a porous dialysis membrane separating blood and filtrate compartments. Results: High levels of oxygen transfer are measured across the oxygenator, while tunable rates of fluid removal, governed by the transmembrane pressure (TMP), are achieved across the UF layer. Key parameters including the blood flow rate, TMP and hematocrit are monitored and compared with computationally predicted performance metrics. Conclusions: These results represent a model demonstration of a potential future clinical therapy where respiratory support and fluid removal are both realized through a single monolithic cartridge. [ABSTRACT FROM AUTHOR]

Background: Various strategies of weaning V‐A ECMO have been described. PCRTO is a weaning technique which involves serial decremental pump revolutions until a retrograde flow from the arterial to venous ECMO cannula is achieved. It has been reported as a feasible weaning strategy in the pediatric population, but its application in adults has not been widely reported. Methods: This was a case series including all adult patients who underwent PCRTO during weaning from V‐A ECMO at a tertiary ECMO center between January 2019 and July 2021. The primary end point was the successful weaning from V‐A ECMO support. Results: A total of 57 runs of PCRTO in 36 patients were analyzed—45 (78.9%) of the trials were concluded successfully. The median retrograde blood flow rate during PCRTO was 0.6 ± 0.2 L/min, and the median duration of each PCRTO was 180 (120–240) min. Of the 35 patients who had at least one session of successful PCRTO, 31 (88.6%) were ultimately weaned from ECMO. There were no major complications from PCRTO including systemic or circuit thrombosis. Conclusions: PCRTO is a feasible strategy for assessing readiness for weaning from V‐A ECMO with a low risk of adverse events and high rate of predicting eventual successful ECMO decannulation. Further investigation including comparison with alternative weaning strategies in prospective studies is required to confirm the approach. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to assess the interdependence of extracorporeal blood flow (Qec) and gas flow (GF) in predicting CO2 removal and reduction of minute mechanical ventilation under extracorporeal respiratory support. Methods: All patients who benefited from V‐V ECMO and high‐flow ECCO2R in our intensive care unit over a period of 18 months were included. CO2 removal was calculated from inlet/outlet blood port gases during the first 7 days of oxygenator use. The relationship between the Qec × GF product (named decarboxylation index and expressed in L2/min2) and CO2 removal or expired minute mechanical ventilation reduction (ECMV ratio) was studied using linear regression models. Results: Eighteen patients were analyzed, corresponding to 24 oxygenators and 261 datasets. CO2 removal was 393 ml/min (IQR, 310–526) for 1.8 m2 oxygenators and 179 ml/min (IQR, 165–235) for 1.3 m2 oxygenators. The decarboxylation index was associated linearly with CO2 removal (R2 = 0.62 and R2 = 0.77 for the two oxygenators, respectively) and ECMV ratio (R2 = 0.72 and R2 = 0.62, respectively). The 20L2/min2 value (considering Qec = 2 L/min and GF = 10 L/min) was associated with an ECMV ratio between 61% and 29% for 1.8 m2 oxygenators, and between 62% and 38% for 1.3 m2 oxygenators. Conclusion: The decarboxylation index is a simple parameter to predict CO2 removal and ECMV ratio under extracorporeal respiratory support. [ABSTRACT FROM AUTHOR]

Background: The purpose of this research is to address ongoing device shortfalls for pediatric patients by developing a novel pediatric hybrid total artificial heart (TAH). The valveless magnetically‐levitated MCS device (Dragon Heart) has only two moving parts, integrates an axial and centrifugal blood pump into a single device, and will occupy a compact footprint within the chest for the pediatric patient population. Methods: Prior work on the Dragon Heart focused on the development of pump designs to achieve hemodynamic requirements. The impeller of these pumps was shaft‐driven and thus could not be integrated for testing. The presented research leverages an existing magnetically levitated axial flow pump and focuses on centrifugal pump development. Using the axial pump diameter as a geometric constraint, a shaftless, magnetically supported centrifugal pump was designed for placement circumferentially around the axial pump domain. The new design process included the computational analysis of more than 50 potential centrifugal impeller geometries. The resulting centrifugal pump designs were prototyped and tested for levitation and no‐load rotation, followed by in vitro testing using a blood analog. To meet physiologic demands, target performance goals were pressure rises exceeding 90 mm Hg for flow rates of 1–5 L/min with operating speeds of less than 5000 RPM. Results: Three puck‐shaped, channel impellers for the centrifugal blood pump were selected based on achieving performance and space requirements for magnetic integration. A quasi‐steady flow analysis revealed that the impeller rotational position led to a pulsatile component in the pressure generation. After prototyping, the centrifugal prototypes (3, 4, and 5 channeled designs) demonstrated levitation and no‐load rotation. Hydraulic experiments established pressure generation capabilities beyond target requirements. The pressure‐flow performance of the prototypes followed expected trends with a dependence on rotational speed. Pulsatile blood flow was observed without pump‐speed modulation due to rotating channel passage frequency. Conclusion: The results are promising in the advancement of this pediatric TAH. The channeled impeller design creates pressure‐flow curves that are decoupled from the flow rate, a benefit that could reduce the required controller inputs and improve treatment of hypertensive patients. [ABSTRACT FROM AUTHOR]

Left ventricular assist device (LVAD) has emerged as an effective surgical therapy for end‐stage heart failure. In an attempt to reduce invasiveness and avoid difficult sternal re‐entries, alternative surgical approaches have been adopted. In particular, when the thoracic aorta is severely diseased or difficult to expose, subclavian arteries could serve as site for outflow graft anastomosis. However, major concerns regarding the utilization of subclavian arteries are the small caliber of these vessels that could lead to inadequate LVAD flow, arm complications related to excessive blood flow, and possible outflow graft compression. In the present case series, we describe an innovative technique for LVAD implantation, in which the left subclavian artery was employed as an outflow graft anastomosis site, and the left ventricular apex was approached through a mini‐thoracotomy. Technical issues were considered to prevent possible complications: the adequacy of left subclavian artery diameter, the banding of the artery distal to the anastomosis site to limit left arm overflow, and the outflow graft covering with a reinforced vascular graft to avoid any external compression. During follow‐up, the technique reported was found to be effective in ensuring good LVAD function and flow, and no complications related to the procedure were reported. [ABSTRACT FROM AUTHOR]

To visualize the flow of red blood cells through a 3D‐printed material, I imagined the scene as a landscape from 'Fantastic Voyage.' I aimed to use dramatic backlighting and a contrasting rim light to enhance the perspective of blood permeability and flow on a microscopic level.. [Extracted from the article]

The increasing prevalence of chronic lung disease worldwide, combined with the emergence of multiple pandemics arising from respiratory viruses over the past century, highlights the need for safer and efficacious means for providing artificial lung support. Mechanical ventilation is currently used for the vast majority of patients suffering from acute and chronic lung failure, but risks further injury or infection to the patient's already compromised lung function. Extracorporeal membrane oxygenation (ECMO) has emerged as a means of providing direct gas exchange with the blood, but limited access to the technology and the complexity of the blood circuit have prevented the broader expansion of its use. A promising avenue toward simplifying and minimizing complications arising from the blood circuit, microfluidics‐based artificial organ support, has emerged over the past decade as an opportunity to overcome many of the fundamental limitations of the current standard for ECMO cartridges, hollow fiber membrane oxygenators. The power of microfluidics technology for this application stems from its ability to recapitulate key aspects of physiological microcirculation, including the small dimensions of blood vessel structures and gas transfer membranes. An even greater advantage of microfluidics, the ability to configure blood flow patterns that mimic the smooth, branching nature of vascular networks, holds the potential to reduce the incidence of clotting and bleeding and to minimize reliance on anticoagulants. Here, we summarize recent progress and address future directions and goals for this potentially transformative approach to artificial lung support. Correspondence between native blood vessel branching and the microfluidic blood vessel branching patterns that form the design basis for bio‐inspired artificial organs. As in the physiological vasculature, a large inlet vessel branches into multiple trunk lines, each of which leads to further branching into smaller microchannels. This design paradigm preserves a smooth distribution of blood flow throughout the microfluidic network. [ABSTRACT FROM AUTHOR]

By the year 2000, there was rising interest in home hemodialysis in the United States. HemoCleanse decided to resurrect the BioLogic‐HD machine, using updated components. A spin‐off company Renal Solutions (RSI) created the Allient™, with sorbent regeneration of dialysate, hollow fiber dialyzer, pressure‐controlled blood flow rate, controlled filtration, and single‐ or dual‐needle access. RSI merged with Sorb Technology and the Allient™ was built, tested, and FDA‐approved to market. In 2007 Fresenius Medical Corporation (FMC) bought RSI. FMC began an extensive re‐design of the machine to fit the needs of both in‐center and home dialysis. The redesigned machine never was marketed. [ABSTRACT FROM AUTHOR]

Background: Hemodialysis (HD) using super high‐flux dialyzer (HD + SHF) comparably removed uremic toxins to high‐volume postdilution online hemodiafiltration (olHDF). Integration of hemoperfusion (HP) to HD + SHF (HD + SHF + HP) might provide superior uremic toxin removing capability to high‐volume postdilution olHDF. Method: The present study was conducted in thrice‐a‐week HD patients to compare the efficacy in removing indoxyl sulfate (IS), beta‐2 microglobulin (β2M), and urea between high‐volume postdilution ol‐HDF and HD + SHF + HP, comprising HD + SHF as the main treatment plus HD + SHF + HP 1/week in the first 4 weeks and 1/2 weeks in the second 4 weeks. Results: Ten prevalent HD patients with blood flow rate (BFR) above 400 ml/min were randomized into two sequences of 8‐week treatment periods of HD + SHF + HP and later high‐volume postdilution olHDF or vice versa. When compared with high‐volume postdilution olHDF (convective volume of 26.02 ± 1.8 L/session), HD + SHF + HP provided comparable values of percentage reduction ratio of IS (52.0 ± 11.7 vs. 56.3 ± 7.5%, p = 0.14) and β2M (83.7 ± 4.9 vs. 84.0 ± 4.3%, p = 0.37) and slightly lower urea reduction ratio. Despite greater dialysate albumin loss (p = 0.008), there was no significant change in serum albumin level in HD + SHF + HP group. Conclusions: HD + SHF + HP could not provide superior efficacy in removing uremic toxins to high‐volume postdilution olHDF. The use of low BFR of 200 ml/min during the first 2 h of HD + SHF + HP session, according to the instruction of manufacturer, might impair the efficacy of the HD + SHF part in removing uremic toxins. [ABSTRACT FROM AUTHOR]

Background: Patients with end‐stage, biventricular heart failure, and for whom heart transplantation is not an option, may be given a Total Artificial Heart (TAH). The Realheart® is a novel TAH which pumps blood by mimicking the native heart with translation of an atrioventricular plane. The aim of this work was to create a strategy for using Computational Fluid Dynamics (CFD) to simulate haemodynamics in the Realheart®, including motion of the atrioventricular plane and valves. Methods: The accuracies of four different computational methods for simulating fluid‐structure interaction of the prosthetic valves were assessed by comparison of chamber pressures and flow rates with experimental measurements. The four strategies were: prescribed motion of valves opening and closing at the atrioventricular plane extrema; simulation of fluid‐structure interaction of both valves; prescribed motion of the mitral valve with simulation of fluid‐structure interaction of the aortic valve; motion of both valves prescribed from video analysis of experiments. Results: The most accurate strategy (error in ventricular pressure of 6%, error in flow rate of 5%) used video‐prescribed motion. With the Realheart operating at 80 bpm, the power consumption was 1.03 W, maximum shear stress was 15 Pa, and washout of the ventricle chamber after 4 cycles was 87%. Conclusions: This study, the first CFD analysis of this novel TAH, demonstrates that good agreement between computational and experimental data can be achieved. This method will therefore enable future optimisation of the geometry and motion of the Realheart®. [ABSTRACT FROM AUTHOR]

Background: Arterial compliance assists the cardiovascular system with three key roles: (i) storing up to 50% of the stroke volume; (ii) ensuring blood flow during diastole; (iii) dampening pressure oscillations through arterial distension. In mock circulation loops (MCLs), arterial compliance was simulated either with membrane, spring, or Windkessel chambers. Although they have been shown to be suitable for cardiac device testing, their passive behavior can limit stress‐based testing of arteries. Here we present an active compliance chamber with a feedback control of variable compliance as part of an MCL designed for biomechanical evaluation of arteries under physiological waveforms. Materials and Methods: The chamber encloses a piston that changes the volume via a cascaded controller when there is a difference between the real‐time pressure and the physiological reference pressure with the aim to equilibrate both pressures. Results: The experimental results showed repeatable physiological waveforms of aortic pressure in health (80–120 mm Hg), systemic hypertension (90–153 mm Hg), and heart failure reduced ejection fraction (78–108 mm Hg). Statistical validation (n = 20) of the function of the chamber is presented against compared raw data. Conclusion: We demonstrate that the active compliance chamber can track the actual pressure of the MCL and balance it in real time (every millisecond) with the reference values in order to shape the given pressure waveform. The active compliance chamber is an advanced tool for MCL applications for biomechanical examination of stented arteries and for preclinical evaluation of vascular implants. [ABSTRACT FROM AUTHOR]

We present an updated overview of the literature comparing normothermic with hypothermic machine perfusion in porcine kidneys. We conducted a systematic literature review in Embase, Medline Epub (Ovid), Cochrane Central, Web of Science, and Google Scholar on studies comparing normothermic (NMP) to hypothermic machine perfusion (HMP) in porcine kidneys. A meta‐analysis was judged inappropriate because of heterogeneity in study design and perfusion methods. The quality of evidence of each included study was assessed. We included 8 studies. One out of 5 studies reported a significant difference in peak renal blood flow in favor of NMP. Oxygen consumption was significantly higher in NMP kidneys in 2 out of 5 studies. Peak creatinine clearance in NMP was significantly higher than that in HMP in 1 out of 6 studies. Two out of 4 studies reported a higher degree of epithelial vacuolation in kidneys receiving NMP over HMP. None of the studies found a significant difference between NMP and HMP in peak serum creatinine or graft survival after autotransplantation. The results need to be interpreted with caution in view of the diversity in perfusion protocols, the low quality of evidence, and the limited sample sizes. [ABSTRACT FROM AUTHOR]

Severe accidental hypothermia carries high mortality and morbidity and is often treated with invasive extracorporeal methods. Continuous veno‐venous hemodiafiltration (CVVHDF) is widely available in intensive care units. We sought to provide theoretical basis for CVVHDF use in rewarming of hypothermic patients. CVVHDF system was used in the laboratory setting. Heat balance and transferred heat units were evaluated for the system without using blood. We used 5L of crystalloid solution at the temperature of approximately 25°C, placed in a thermally insulated tank (representing the "central compartment" of a hypothermic patient). Time of warming the central compartment from 24.9 to 30.0°C was assessed with different flow combinations: "blood" (central compartment fluid) 50 or 100 or 150 mL/min, dialysate solution 100 or 1500 mL/h, and substitution fluid 0 or 500 mL/h. The total circulation time was 1535 minutes. There were no differences between heat gain values on the filter depending on blood flow (P =.53) or dialysate flow (P =.2). The mean heating time for "blood" flow rates 50, 100, and 150 mL/min was 113.7 minutes (95% CI, 104.9‐122.6 minutes), 83.3 minutes (95% CI, 76.2‐90.3 minutes), and 74.7 minutes (95% CI, 62.6‐86.9 minutes), respectively (P <.01). The respective median rewarming rate for different "blood" flows was 3.6°C/h (IQR, 3.0‐4.2°C/h), 4.8 (IQR, 4.2‐5.4°C/h), and 5.4 (IQR, 4.8‐6.0°C/h), respectively (P <.01). The dialysate flow did not affect the warming rate. Based on our experimental model, CVVHDF may be used for extracorporeal rewarming, with the rewarming rates increasing achieved with higher blood flow rates. [ABSTRACT FROM AUTHOR]

Advances in microfluidics technologies have spurred the development of a new generation of microfluidic respiratory assist devices, constructed using microfabrication techniques capable of producing microchannel dimensions similar to those found in human capillaries and gas transfer films in the same thickness range as the alveolar membrane. These devices have been tested in laboratory settings and in some cases in extracorporeal animal experiments, yet none have been advanced to human clinical studies. A major challenge in the development of microfluidic oxygenators is the difficulty in scaling the technology toward high blood flows necessary to support adult humans; such scaling efforts are often limited by the complexity of the fabrication process and the manner in which blood is distributed in a three‐dimensional network of microchannels. Conceptually, a central advantage of microfluidic oxygenators over existing hollow‐fiber membrane‐based configurations is the potential for shallower channels and thinner gas transfer membranes, features that reduce oxygen diffusion distances, to result in a higher gas transfer efficiency defined as the ratio of the volume of oxygen transferred to the blood per unit time to the active surface area of the gas transfer membrane. If this ratio is not significantly higher than values reported for hollow fiber membrane oxygenators (HFMO), then the expected advantage of the microfluidic approach would not be realized in practice, potentially due to challenges encountered in blood distribution strategies when scaling microfluidic designs to higher flow rates. Here, we report on scaling of a microfluidic oxygenator design from 4 to 92 mL/min blood flow, within an order of magnitude of the flow rate required for neonatal applications. This scaled device is shown to have a gas transfer efficiency higher than any other reported system in the literature, including other microfluidic prototypes and commercial HFMO cartridges. While the high oxygen transfer efficiency is a promising advance toward clinical scaling of a microfluidic architecture, it is accompanied by an excessive blood pressure drop in the circuit, arising from a combination of shallow gas transfer channels and equally shallow distribution manifolds. Therefore, next‐generation microfluidic oxygenators will require novel design and fabrication strategies to minimize pressure drops while maintaining very high oxygen transfer efficiencies. [ABSTRACT FROM AUTHOR]

Extracorporeal carbon dioxide removal (ECCO2R) is a low blood flow veno‐venous extracorporeal membrane oxygenation technique that provides artificial blood CO2 removal. Recently, a new ECCO2R system (PrismaLung), providing very low blood flow has been commercialized. The aim of this study is to report its use in severe chronic obstructive pulmonary disease (COPD) patients needing an ECCO2R therapy. Six severe COPD patients with acute exacerbation leading to refractory hypercapnic respiratory acidosis were treated with ECCO2R therapy. Two different systems were used: a PrismaLung system and a conventional ECCO2R device. The maximum blood flow provided by PrismaLung was significantly lower than that with the conventional ECCO2R system. In three patients initially treated with PrismaLung, there were no improvements in pH, PaCO2, or RR. Thus, the therapy was switched to a conventional ECCO2R system in these three patients, and three others were treated from the outset by the conventional ECCO2R system, providing significant improvement in pH, PaCO2, and RR. The present retrospective study describes the first use of PrismaLung in severe COPD patients with acute exacerbation. When compared with a higher blood flow ECCO2R system, our results show that this novel, very low‐flow device is not able to remove sufficient CO2, normalize pH or decrease respiratory rate. [ABSTRACT FROM AUTHOR]

Continuous flow left ventricular assist devices (LVADs) have become a valuable therapy for end‐stage heart failure. In vitro research highlighted a role of outflow cannula position on the pattern of blood flow in the aorta. However, the clinical effects of the alterations of flow remain unclear. We investigate short‐ and long‐term outcomes of patients implanted with Jarvik 2000 LVAD, according to the ascending (Group 1) versus descending (Group 2) outflow graft connection to the aorta in a multicenter study. From May 2008 to October 2014, 140 consecutive end‐stage heart failure patients underwent Jarvik 2000 LVAD implantation in 17 Italian centers. According with a preliminary multivariate analysis, we selected the 90 patients implanted in the four high‐volume centers to avoid bias (Group 1 n = 39, Group 2 n = 51). Among the groups, no differences were recorded in the hospital mortality and the main complications occurring after LVAD implantation were similar. In multivariable analysis, the ascending aorta outflow cannula position and higher creatinine at discharge were significant predictors for long‐term survival. Postimplant hemolysis was more pronounced in descending aorta outflow graft anastomosis. Outflow graft anastomosis to the ascending aorta is associated with better long‐term survival, independent of age and perfusion techniques, reflecting the previous in vitro results. [ABSTRACT FROM AUTHOR]

Intraventricular blood stasis is a design consideration for continuous flow blood pumps and might contribute to adverse events such as thrombosis and ventricular suction. However, the blood flow inside left ventricles (LVs) supported by blood pumps is still unclear. In vitro experiments were conducted to imitate how the hydraulic performance of an axial blood pump affects the intraventricular blood flow of a severe heart failure patient, such as velocity distribution, vorticity, and standard deviation of velocity. In this study, a silicone model of the LV was constructed from the computed tomography data of one patient with heart failure and was 3D printed. Then, intraventricular flow was visualized by particle image velocimetry equipment within a mock circulation loop. The results showed that the axial blood pump suctions most of the blood in a severely failing LV, there was an altered flow status within the LV, and blood stasis appeared in the central region of the LV. Some blood may be suctioned from the aortic valve to the blood pump because the patient's native heart was severely failing. Blood stasis at the LV center may cause thrombosis in the LV. The vortex flow near the inner wall of the LV can thoroughly wash the left ventricular cavity. [ABSTRACT FROM AUTHOR]

Biocompatibility of ventricular assist devices (VADs) has been steadily improving, yet the rate of neurological events remains unacceptably high. Recent speculation for elevated stroke rates centers on ingestion of thrombi originating upstream of the pump, such as in the ventricle or left atrial appendage. These thrombi may be ejected by the VAD or become deposited within the blood flow pathway, presenting serious complications to the patient. This study was performed to visualize and quantify the degree of disruption, adherence, and disintegration of thrombi that are ingested by the three most implanted VADs: the HeartMate II, HeartMate 3, and HVAD. Clot analogs of varying microstructure compositions (red, white) and sizes (0.5, 1, 2 cm3) were synthesized in vitro based on clinical explant data. These were introduced individually into an in vitro flow loop with a transparent replica of the HMII, HM3, and HVAD operated at nominal steady flow (2.3‐4.0 L/min). High‐speed videography (up to 10 000 fps) revealed the ingestion, disruption, ejection, and adherence of thrombus fragments. Thromboemboli of varying compositions and sizes were observed mechanically attaching to components in all 3 VAD models. In some instances, ingested thrombi physically obstructed portions of the blood flow path; 18% (3 of 17 total) of red thrombi adhered to the inflow straightener of the transparent HMII. In the HVAD model, fewer than 4% of clots were adherent or trapped within the pump, irrespective of microstructure or initial volume. In comparison, 100% (4 of 4 total) of 1‐cm3 white (fibrin) clots became lodged within the transparent HM3 while, in contrast, less than 5% of macerated red clots (3 of 63 total) of the same volume were adherent inside the pump. A significant proportion of ingested thrombi were macerated into infinitesimal fragments; 84% and 74% of 2‐cm3 red thrombi in the HVAD and HM3 models, respectively, were found to have disintegrated upon ingestion. However, large emboli were also discharged from both centrifugal VADs; these fragments, ranging from 0.01 to 0.29 cm3 regardless of microstructure and original volume, may be capable of occluding an intracranial vessel. Therefore, ingested thrombus may explain, in part, elevated stroke rates in contemporary blood pumps in the absence of adherent pump thrombosis. [ABSTRACT FROM AUTHOR]

Advanced glycosylation end‐products (AGEs) are reported to be a risk factor for cardiovascular mortality in hemodialysis (HD) patients. As serum AGEs can change with dialysis, measurement of AGEs deposited in the skin by autofluorescence (SAF) is now a recognized method of measuring AGEs. An arteriovenous fistula (AVF) is the preferred way to access blood in HD patients, and as the creation of an AVF changes blood flow distribution in the arm, we wished to determine whether this affected SAF deposition in the skin. SAF was measured using the AGE reader, which directs ultraviolet light at an intensity range of 300‐420 nm (peak 370 nm) in the arms of HD patients dialyzing with an AVF. We measured SAF in 267 patients, 60.3% male, 46.1% diabetic, median duration of dialysis 34.7 (15.1‐64.2) months with AVF. The median SAF was lower in the AVF arm (median 3.4 (2.9‐4.2) vs. 3.7 (3.2‐4.5) AU, P <.001), and for the 160 patients with an upper arm AVF (3.5 (2.9‐4.3) vs. 3.8 (3.2‐4.5) AU, P <.001), but not for the 107 patients dialyzing with a forearm AVF ((3.4 (2.8‐4.2) vs. 3.6 (3.0‐4.5) AU, P =.085). Blood flow was greater for upper arm AVF compared to forearm AVFs (1190 (770‐1960) vs. (930 (653‐1250) mL/min, P =.007), but there was no association between blood flow and SAF (P >.05). AVF alters blood flow in the arm, and we found that SAF measurements were lower in the arm with AVF. We suggest that SAF measurements are made in the non‐AVF arm. [ABSTRACT FROM AUTHOR]

Pulsatile ventricular assist devices (pVADs) yield a blood flow that imitates the pulsatile flow of the heart and, therefore, could diminish the adverse events related to the continuous flow provided by the ventricular assist devices that are commonly used. However, their intrinsic characteristics of larger size and higher weight set a burden to their implantation, that along with the frequent mechanical failures and thrombosis events, reduce the usage of pVADs in the clinical environment. In this study, we investigated the possibility to reduce the pump size by using high pump stroke ratios while maintaining the ability to control the hemodynamics of the cardiovascular system (CVS). In vitro and in vivo experiments were conducted with a custom pVAD implemented on a hybrid mock circulation system and in five sheep, respectively. The actuation of the pVAD was synchronized with the heartbeat. Variations of the pump stroke ratio, time delay between the pump stroke and the heart stroke, as well as duration of the pump systole in respect to the total cardiac cycle duration were used to evaluate the effects of various pump settings on the hemodynamics of the CVS. The results suggest that by varying the operating settings of the pVAD, a pulsatile flow that provides physiological hemodynamic parameters, as well as a control over the hemodynamic parameters, can be achieved. Additionally, by employing high pump stroke ratios, the size of the pVAD can be significantly reduced; however, at those high pump stroke ratios, the effect of the other pump parameters diminishes. [ABSTRACT FROM AUTHOR]

The aim of the study was to compare expanded hemodialysis (HDx) with hemodiafiltration (HDF) at different infusion flows to identify the main determinants, namely blood flow (Qb), replacement volume, infusion flow (Qi), ultrafiltration flow (Quf), filtration fraction (FF), and the point at which the effectiveness of HDF equals or exceeds that of HDx. We conducted a prospective, single‐center study in 12 patients. Each patient underwent 12 dialysis sessions: six sessions with Qb 350 and six with Qb 400 mL/min; with each Qb, one session was with HDx and five sessions were with FX80 (one in HD, and four with Qi 50, 75, 90/100 mL/min or autosubstitution in postdilution HDF). The reduction ratios (RR) of urea, creatinine, ß2‐microglobulin, myoglobin, prolactin, α1‐microglobulin, α1‐acid glycoprotein, and albumin were compared intraindividually and the global removal score (GRS) was calculated. The mean replacement volume with Qb 350 mL/min was 13.77 ± 0.92 L with Qi 50 mL/min, 20.75 ± 1.17 L with Qi 75, 23.83 ± 1.92 L with Qi 90, and 27.51 ± 2.77 L with autosubstitution. Similar results were obtained with Qb 400 mL/min, and the results were only slightly higher with Qi 100 mL/min or in autosubstitution. The GRS was positively correlated with replacement volume with Qb 350 (R2 = 0.583) and with Qb 400 (R2 = 0.584); with Quf with Qb 350 (R2 = 0.556) and with Qb 400 (R2 = 0.604); and also with FF with Qb 350 (R2 = 0.556) and with Qb 400 mL/min (R2 = 0.603). The minimum convective volume in HDF from which it is possible to overcome the efficacy of HDx was 19.2 L with Qb 350 and 17.6 L with Qb 400 mL/min. The cut‐off point of Quf at which HDF exceeded the effectiveness of HDx was 80.6 mL/min with Qb 350 and 74.1 mL/min with Qb 400 mL/min. The cut‐off point at which FF in HDF exceeded the effectiveness of the HDx was 23.0% with Qb 350 and 18.6% with Qb 400 mL/min. In conclusion, this study confirms the superiority of postdilution HDF over HDx when replacement volume, convective volume, Quf, or FF exceeds certain values. Increasing the Qb in postdilution HDF manages to increase the convective dose and more easily overcome the HDx. [ABSTRACT FROM AUTHOR]

Limited donor organs and alternative therapies have led to a growing interest in the use of blood pumps as a treatment strategy for patients with single functional ventricle. The present study examines the use of collapsible and flexible impeller, cage, and diffuser designs of an axial blood pump for Fontan patients. Using one‐way fluid‐structure interaction (FSI) studies, the impact of blade deformation on blood damage and pump performance was investigated for flexible impellers. We evaluated biocompatible materials, including Nitinol, Bionate 80A polyurethane, and silicone for flow rates between 2.0‐4.0 L/min and rotational speeds of 3000‐9000 rpm. The level of deformation experienced by a cage and diffuser made of surgical stainless steel (control), Nitinol, and Bionate 80A polyurethane was also predicted using one‐way FSI. The fluid pressure on the surface of the impeller, cage, and diffuser was determined using computational fluid dynamics (CFD), and then, the surface pressure was exported and used to investigate the impeller, cage, and diffuser deformation using finite element analysis. Finally, deformed impeller geometries were imported into the CFD software to determine the implication of deformation on pressure generation, blood damage index, and fluid streamlines. It was found that rotational speed, and not flow rate, is the largest determinant of impeller deformation, occurring at the blade trailing edges. The models predicted the maximum impeller deformation for Nitinol to be 40 nm, Bionate 80A polyurethane to be 106 μm, and silicone to be 2.8 mm, all occurring at 9000 rpm. The effects of silicone deformation on performance were significant, particularly at speeds above 5000 rpm where a decrease in pressure generation of more than 10% was observed. Despite this loss, the pressure generation at 5000 rpm exceeded the level required to alleviate Fontan complications. A blood damage estimation was performed and levels remained low. The effect of significant impeller deformation on blood damage was inconsistent and requires additional investigation. Cage and diffuser geometries made of steel and Nitinol deformed minimally but Bionate 80A experienced unacceptable levels of deformation, particularly in the free‐flow case without a spinning impeller. These results support the continued evaluation of a flexible, pitch‐adjusting, axial‐flow, mechanical assist device as a clinical therapeutic option for patients with dysfunctional Fontan physiology. [ABSTRACT FROM AUTHOR]

Severe aortic insufficiency (AI) after implantation of continuous‐flow left ventricular‐assist device (LVAD) affects device performance and outcomes. However, the mechanism for the occurrence and progression of AI has not been elucidated. We investigated the impact of nonphysiological retrograde blood flow in the aortic root on AI after LVAD implantation. Blood flow pattern was analyzed in patients with and without AI (n = 3 each) who underwent LVAD implantation, by computational fluid dynamics with patient‐specific geometries, which were reproduced using electrocardiogram‐gated 320‐slice computed tomographic images. The total volume of retrograde blood flow during one cardiac cycle (716 ± 88 mL) was higher and the volume of slow blood flow (<0.1 cm/s) (0.16 ± 0.04 cm3) was lower in patients with AI than in those without AI (360 ± 111 mL, P =.0495, and 0.49 ± 0.08 cm3, P =.0495, respectively). No significant difference in wall shear stress on the aortic valve was observed between the groups. Patients with AI had a perpendicular anastomosis at the distal ascending aorta and the simulation in the modified anastomosis model of patients with AI showed that the retrograde blood flow pattern depended on the angle and position of anastomosis. Computational fluid dynamics revealed strong retrograde blood flow in the ascending aorta and aortic root in patients with AI after LVAD implantation. The angle and position of LVAD outflow anastomosis might impact retrograde blood flow and de novo AI after LVAD implantation. [ABSTRACT FROM AUTHOR]

Continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA) in newborns and infants is challenging and accumulation of citrate can occur. There are only a few studies reporting the detailed data on RCA. We aimed to analyze RCA‐CRRT at our institution with focus on citrate accumulation. Critically ill newborns and infants up to 11 kg of body weight (BW), treated with RCA‐CRRT in the 2011‐2016 period were included in this retrospective observational study. Prismaflex(R) and Multifiltrate‐CiCa(R) dialysis monitors were used with either automated or manual RCA. Data was collected regarding the circuit lifetime, parameters of RCA, markers of citrate accumulation (total/ionized calcium ratio > 2.5), and metabolic complications. We included 10 children with mean age of 2.6 ± 3.8 months and BW of 4.6 ± 2.7 kg. In‐hospital mortality was 60%. RCA‐CRRT parameters were: blood flow 46 ± 9 mL/min (12 ± 5 mL/min/kg BW), citrate dose 2.8 ± 0.6 mmol/L of blood resulting in estimated citrate load to the patient of 1.7 ± 0.8 mmol/h/kg BW. In total, 57 dialysis circuits were used with mean filter lifetime of 39 ± 29 h. Citrate accumulation (total/ionized calcium ratio > 2.5) was observed in 7/10 patients and in 14/57 (25%) of circuits; those circuits were performed in children with lower age and BW, had higher relative blood flow and citrate load, while citrate dose was similar. When citrate load to the patient was used to predict citrate accumulation, AUC under the ROC curve was 0.78 and 1.7 mmol/h/kg BW was considered the optimal cutoff value (sensitivity 71% and specificity 72%). CRRT with RCA using equipment, developed for adult population, is feasible in newborns and infants. Signs of citrate accumulation developed relatively often. To prevent it, we suggest avoiding citrate loads above 1.7 mmol/h/kg BW, which can best be achieved by keeping the blood flow below 9 mL/min/kg BW. [ABSTRACT FROM AUTHOR]

Extracorporeal membrane oxygenation (ECMO) has become a mainstay of therapy for patients suffering from severe respiratory failure. Ambulatory ECMO systems aim to provide long‐term out‐of‐hospital respiratory support. As a patient's activity level changes, the required level of ECMO support varies with oxygen consumption and metabolic fluctuations. To compensate for such changes, an autoregulatory ECMO system (AR‐ECMO) has been developed and its performance was evaluated as a proof of concept in an acute ovine model. The AR‐ECMO system consists of a regular ECMO circuit and an electromechanical control system. A custom fuzzy logic control algorithm was implemented to adjust the blood flow and sweep gas flow of the ECMO circuit to meet the varying respiratory demand by utilizing two noninvasive sensors for venous oxyhemoglobin saturation and the oxygenator exhaust gas CO2 concentration. Disturbance responses of the AR‐ECMO to induced acute respiratory distress were assessed for six hours in four juvenile sheep cannulated with a veno‐pulmonary artery ECMO configuration, including acute ventilator shutoff, ventilator step change (off‐on‐off), and forced desaturation. All sheep survived for the study duration. The AR‐ECMO system was able to respond and maintain stable hemodynamics and physiological blood gas contents (SpO2 = 96.3 % ± 4.29, pH 7.44 ± 0.09, pCO2 = 38.9 ± 9.9 mm Hg, and pO2 =237.9 ± 123.6 mm Hg) during simulated respiratory distress. Acceptable correlation between oxygenator exhaust gas CO2 and oxygenator outlet pCO2 were observed (R2 = 0.84). In summary, the AR‐ECMO system successfully maintained physiologic control of peripheral oxygenation and carbon dioxide over the study period, utilizing only measurements taken directly from the ECMO circuit. The range of system response necessitates an adaptable system in the setting of variable metabolic demands. The ability of this system to respond to significant disturbances in ventilator support is encouraging. Future work to evaluate our AR‐ECMO system in long‐term, awake animal studies is necessary for further refinement. [ABSTRACT FROM AUTHOR]

Continuous‐flow left ventricular assist devices (LVADs) reduce peak systolic flow, increase diastolic flow, and eliminate pulsatility of circulation. Altered blood flow may lead to a change in end‐organ perfusion. Analysis of the flow dynamics of the arteries of end organs, such as the brain, may indicate whether an organ is perfused sufficiently. The aim of this study is to evaluate and identify the flow pattern changes of carotid (CA) and middle cerebral arteries (MCA) in LVAD patients and to compare with heart failure patients and healthy volunteers. Eighty‐nine individuals were included in this cross‐sectional study. Participants were divided into three groups: LVAD patients (n = 31), heart failure patients (n = 26), and healthy volunteers (n = 27). Carotid and transcranial Doppler ultrasonography were performed for all study groups for peak systolic velocity (PSV), end‐diastolic velocity (EDV), pulsatility (PI), and resistive (RI) indices of CA and MCA. Flow dynamics were compared between the groups. Doppler ultrasonographic data were analyzed at a median 12 (3‐47) months after LVAD implantation. CA‐PSV was lower in LVAD group compared with the other two groups (P <.001), MCA‐PSV of LVAD and heart failure groups were similar and lower than healthy volunteers (P <.05). The highest values for CA‐EDV were found in the LVAD group (P <.05). MCA‐EDV values were found to be lowest in heart failure group (P <.05). For PI and RI, in all CA and MCA, the LVAD group had lower indices compared with the other two groups (P <.001). In addition, MCA flow analysis in patients with LVADs was identified for the first time with this study. [ABSTRACT FROM AUTHOR]

Extracorporeal circulation using heart‐lung‐machines is associated with a profound activation of corpuscular and plasmatic components of circulating blood, which can also lead to deleterious events such as systemic inflammatory response and hemolysis. Individual components used to install the extracorporeal circulation have an impact on the level of activation, most predominantly membrane oxygenators and hardshell venous reservoirs as used in extracorporeal systems. The blood flows in two different hardshell reservoirs are computationally investigated. A special emphasis is placed on the prediction of an onset of transition and turbulence generation. Reynolds‐averaged numerical simulations (RANS) based on a transitional turbulence model, as well as large eddy simulations (LES) are applied to achieve an accurate prediction. In the LES analysis, the non‐Newtonian behavior of the blood is considered via the Carreau model. Blood damage potential is quantified applying the Modified Index of Hemolysis (MIH) based on the predicted flow fields. The results indicate that the flows in both reservoirs remain predominantly laminar. For one of the reservoirs, considerable turbulence generation is observed near the exit site, caused by the specific design for the connection with the drainage tube. This difference causes the MIH of this reservoir to be nearly twice as large as compared to the alternative design. However, a substantial improvement of these performance criteria can be expected by a local geometry modification. [ABSTRACT FROM AUTHOR]

Left ventricular assist device (LVAD) provides an effective artificial support system to the heart patients. Despite the improved life survival rate, complications like hemolysis, blood trauma, and thrombus formation still limit the performance of the blood pump. The geometrical aspects of blood pumps majorly influence the hemodynamics, therefore these devices must be carefully engineered. In this work, several versions of centrifugal blood pumps are simulated using ANSYS‐CFX to propose a best compatible design for LVAD. A hemodynamic levitation approach for the impeller is also suggested to overcome the cost and weight issue associated with the magnetic levitation. The blood flow is modeled by implementing Bird–Carreau model and its turbulence is solved using the SST turbulence model. The influence of the blade profile, blade tip width, blade numbers, and splitter blades on the hemodynamic characteristics through the pump is observed. An optimum design of centrifugal blood pump for the assistance of failed ventricle is proposed that can effectively pump the blood from the left ventricle to the ascending aorta. The proposal can be adopted by LVAD designers to have hemodynamically tuned efficient product. [ABSTRACT FROM AUTHOR]

The need to simulate the normal operating conditions of the human body is the key factor in every study and engineering process of bioelectronic devices designed for implantation. The Fontan procedure is an example of such a process aimed to support the human body function. It is a standard treatment method for patients with a functionally univentricular heart. However, it has significant drawbacks such as overload of the only functional heart ventricle that often leads to the necessity of the heart transplantation. In this study, we analyze the total cavopulmonary connection (TCPC) influence on the blood with and without connected auxiliary blood circulation pump. We investigate four different types of TCPC configurations, analyze blood pressure and different flow rate, study the turbulent kinetic energy distribution, and evaluate hydraulic and power losses for various cases. Finally, we calculate volumetric scalar shear stresses distribution and demonstrate the high potential of TCPC configuration with connected rotary pump as a tool for the load redistribution in the functional heart ventricle. This work is particularly relevant for improving existing TCPCs' quality that can extend the life of Fontan patients. Moreover, it also applies to the reduction of morbidity and mortality of the patients waiting for the heart transplantation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the hemodynamic properties and microemboli capture associated with different vacuum‐assisted venous drainage (VAVD) vacuum levels and venous reservoir levels in a neonatal cardiopulmonary bypass circuit. Trials were conducted in 2 parallel circuits to compare the performance of Capiox Baby RX05 oxygenator with separate AF02 arterial filter to Capiox FX05 oxygenator with integrated arterial filter. Arterial cannula flow rate to the patient was held at 500 mL/min and temperature maintained at 32°C, while VAVD vacuum levels (0 mm Hg, −15 mm Hg, −30 mm Hg, −45 mm Hg, −60 mm Hg) and venous reservoir levels (50 mL, 200 mL) were evaluated in both oxygenators. Hemodynamic parameters measuring flow, pressure, and total hemodynamic energy were made in real time using a custom‐made data acquisition system and Labview software. Nearly 10 cc bolus of air was injected into the venous line and gaseous microemboli detected using an Emboli Detection and Classification Quantifier. Diverted blood flow via the arterial filter's purge line and mean pressures increased with increasing VAVD levels (P < 0.01). Mean pressures were lower with lower venous reservoir levels and were greater in RX05 groups compared to FX05 (P < 0.01). Microemboli detected at the preoxygenator site increased with higher VAVD vacuum levels and lower venous reservoir levels (P < 0.01). The amount of microemboli captured by the FX05 oxygenator with integrated arterial filter was greater than by the RX05 oxygenator alone, although both oxygenators were able to clear microemboli before reaching the pseudo‐patient. [ABSTRACT FROM AUTHOR]

Spiral/helical forms of blood flow have been observed in large arteries of the cardiovascular system, but their benefits remain underappreciated. Spiral flow has been postulated to improve near‐wall washout, promoting anti‐atherothrombotic conditions. This research aims to study the washout characteristics of spiral flow, specifically, its ability to increase velocity and wall shear stress (WSS) in atherothrombotic‐prone regions. Using 1.2 cm diameter angled test‐conduits (45°, 90°, 135°) with known recirculation/stasis regions at the bend corners, spiral flow washout potential was evaluated in terms of low velocity and low WSS. Two sub‐studies were conducted: the first utilized a spiral flow‐inducing device to enable qualitative analysis of washout‐potential in both computational fluid dynamic (CFD) simulations and benchtop ultrasound visualization; the second used CFD to study the impact of several induced helical wavelengths on the conduit‐dependent recirculation/stasis zones. Physical models of the angled conduits and spiral flow‐inducer were 3D‐printed to facilitate ultrasound visualization. Compared to straight flow, spiral flow generated by the flow‐inducer significantly cleared the recirculation/stasis zones at the corners of the angled conduits. CFD simulations demonstrated that past a geometry‐dependent threshold, increased helical content improved washout, denoted by decreased regions of low velocity and low WSS. Overall, spiral flow markedly improved washout in difficult to reach areas in the angled conduits. This has several important clinical implications: spiral flow shows great promise in reducing blood‐transport‐related complications and can be used to enhance the performance of future medical devices (eg grafts, mechanical circulatory support devices, hemodialysis access ports). [ABSTRACT FROM AUTHOR]

Cardiac implants may have a strong influence on the hemodynamics of the circulatory system. In this study, we aimed at investigating the impact of transcatheter aortic valve implantation (TAVI) devices on blood flow patterns that develop in the ascending aorta under physiological flow conditions in vitro. For this purpose, a noninvasive optical measurement tool, three‐dimensional particle tracking velocimetry (3D‐PTV), was used in a realistic compliant silicone aortic model. The performance and the influence of two TAVIs and one surgical valve on the aortic flow were investigated. Our results showed that valve design and materials may have a distinct influence on relevant hemodynamic properties, namely kinetic energy, production of turbulence, and shear stresses in the ascending aorta. All properties varied considerably between the different valve models. We found that the total aortic regurgitation composed of the closing volume, transvalvular and paravalvular leakages varied for the three valves investigated. Furthermore, peak mean kinetic energy (MKE) ranged from 61 to 116 J/m3, whereas peak turbulent kinetic energy (TKE) ranged from 23 to 36 J/m3. The analysis of shear showed that all the three studied devices had minimal overall risk for thrombus formation. We conclude that the characteristics and material designs of TAVI devices have strong influences on the hemodynamics in the ascending aorta. [ABSTRACT FROM AUTHOR]

Due to the high stroke rate of left ventricular assist device (LVAD) patients, reduction of thrombus has emerged as an important target for LVAD support. Left ventricular blood flow patterns with areas of flow stasis and recirculation are associated with platelet aggregation, which is worsened by exposure to high shear stress. Previous reports of intraventricular thrombus in LVAD patients have identified the outside of the LVAD inflow cannula as a nidus for LV thrombus formation. Previous studies of LVAD inflow cannula design have shown a region of low blood velocity and pulsatility at the apex, adjacent to the cannula. One unresolved question is whether the standard practice of inserting the LVAD inflow cannula several mm into the LV could be revised to reduce thrombus formation. To address this, a "tipless" inflow cannula was designed for the EVAHEART LVAS, and assessed in a mock circulatory loop of the LVAD‐supported heart. Customized transparent silicone models of a dilated LV were connected to the EVAHEART LVAS at the apex with a clear polycarbonate inflow cannula for flow visualization using particle image velocimetry (PIV). The "tipless" cannula was inserted flush with the endocardial border and did not protrude into the LV. This condition was compared to the standard cannula position with a 1‐cm insertion into the LV. The Pre‐LVAD condition corresponded to a severe heart failure patient (ejection fraction of 24%) with a dilated LV (180 mL). LVAD support was provided at speeds of 1.8 and 2.3 krpm. At the lower LVAD speed, 63% of the flow passed through the LVAD, with the remainder ejecting through the aortic valve. When LVAD speed was increased, nearly all flow (98%) left the LV through the LVAD. Both LVAD speed conditions produced a vortex ring similar to the Pre‐LVAD condition in diastole. However, the protruding inflow cannula interrupted the growth and restricted the movement of the vortex, and produced areas of low velocity and pulsatility adjacent to the cannula. The tipless cannula exhibited an uninterrupted pattern of the mitral jet toward the LV apex, which allowed the diastolic vortex to grow and aid in the washout of this region. In addition, the tipless cannula increased aortic valve flow, which reduces stasis in the left ventricular outflow tract. The EVAHEART LVAS tipless inflow cannula design improved regional velocity, pulsatility, and vortex formation compared to the standard protruding design, which all reduce the risk of thrombus formation. The clinical significance of the differences observed in the flow field will be dependent on other factors such as the cannula material and surface characteristics, as well as the patients' coagulation status. [ABSTRACT FROM AUTHOR]

In this study, rear‐impeller axial flow blood pumps (RIAFBP) were developed to realize a trans‐valve axial ventricular assist device (VAD) which consists of the latter blood pump and a polymer monomembrane aortic valve, such as the jellyfish valve. The motor of the RIAFBP is installed in the left ventricle, and its impeller is placed at the aortic valve position. In the prototype RIAFBP, the rotation of the motor is sustained by polyethylene bushings. The RIAFBP has a length of 50 mm and diameter of 19.6 mm. The miniature RIAFBP has the same construction as that of the prototype; however, it employs a ceramic bearing and fin bearing to improve endurance and to reduce blood stagnation. The miniature RIAFBP has a length of 63 mm and diameter of 12 mm. Both RIAFBPs were examined by an in vitro experiment using a 33% glycerin solution. The prototype RIAFBP achieved a maximum pump outflow of 8.5 L/min against a pump head of 100 mm Hg at a rotational speed of 12 000 rpm. The miniature RIAFBP achieved 7 L/min against a pump head of 70 mm Hg at a rotational speed of 21 600 rpm. In conclusion, the miniature RIAFBP has enough pump performance to realize the trans‐valve axial VAD. [ABSTRACT FROM AUTHOR]

Low flow extracorporeal veno‐venous CO2 removal (ECCO2R) therapy is used to remove CO2 while reducing ventilation intensity. However, the use of this technique is limited because efficiency of CO2 removal and potential beneficial effects on pulmonary hemodynamics are not precisely established. Moreover, this technique requires anticoagulation that may induce severe complications in critically ill patients. Therefore, our study aimed at determining precise efficiency of CO2 extraction and its effects on right ventricular (RV) afterload, and comparing regional anticoagulation with citrate to systemic heparin anticoagulation during ECCO2R. This study was performed in an experimental model of severe hypercapnic acidosis performed in two groups of three pigs. In the first group (heparin group), pigs were anticoagulated with a standard protocol of unfractionated heparin while citrate was used for ECCO2R device anticoagulation in the second group (citrate group). After sedation, analgesia and endotracheal intubation, pigs were connected to a volume‐cycled ventilator. Severe hypercapnic acidosis was obtained by reducing tidal volume by 60%. ECCO2R was started in both groups when arterial pH was lower than 7.2. Pump Assisted Lung Protection (PALP, Maquet, Rastatt, Germany) system was used to remove CO2. CO2 extraction, arterial pH, PaCO2 as well as systemic and pulmonary hemodynamic were continuously followed. Mean arterial pH was normalized to 7.37 ± 1.4 at an extracorporeal blood flow of 400 mL/min, coming from 7.11 ± 1.3. RV end‐systolic pressure increased by over 30% during acute hypercapnic acidosis and was normalized in parallel with CO2 removal. CO2 extraction was not significantly increased in citrate group as compared to heparin group. Mean ionized calcium and MAP were significantly lower in the citrate group than in the heparin group during ECCO2R (1.03 ± 0.20 vs. 1.33 ± 0.19 and 57 ± 14 vs. 68 ± 15 mm Hg, respectively). ECCO2R was highly efficient to normalize pH and PaCO2 and to reduce RV afterload resulting from hypercapnic acidosis. Regional anticoagulation with citrate solution was as effective as standard heparin anticoagulation but did not improve CO2 removal and lead to more hypocalcemia and hypotension. [ABSTRACT FROM AUTHOR]

Left ventricle (LV) unloading caused by a left ventricular assist device (LVAD) has been shown to enhance reverse LV remodeling in end‐stage cardiomyopathy. Several reports consistently suggest that a pulsatile‐flow LVAD has more profound effects compared to continuous‐flow LVAD, though the responsible mechanisms are not fully understood. We hypothesized that arterial pulsatility, being affected by the type of LVAD, may affect microvasculature and functional/pathological LV remodeling in end‐stage cardiomyopathy. The study included 18 patients with chronic heart failure who underwent LVAD implantation. Eight patients were implanted with pulsatile‐flow LVAD, and 10 patients were implanted with continuous‐flow LVAD. The results of serial echocardiograms and histopathological assessment of transmural LV tissues, which were collected during the implantation and removal of LVADs, were compared between the groups. The results of echocardiography showed that LV systolic dimension and LV ejection fraction improved greatly in the pulsatile‐flow LVAD group compared to the continuous‐flow LVAD group. Histological analysis showed that in both groups, increased microvasculature density and decreased cardiomyocyte size during LVAD support had no significant difference. In contrast, only the patients with continuous‐flow LVADs had presented with significant increase in α‐smooth muscle actin (α‐SMA)‐positive layer thickness and the number of proliferating cell nuclear antigen (PCNA)‐positive cells of myocardial arterioles. We concluded that the use of long‐term continuous‐flow LVAD support, having less pulsatility, had induced more thickening to the medial layer of myocardial arterioles compared to the use of pulsatile‐flow LVADs. Our findings suggest that the pathological impairment of myocardial microvascular structure during continuous‐flow LVAD support may be a novel mechanism which accounts for the difference in LV remodeling depending on the type of LVAD. [ABSTRACT FROM AUTHOR]

Noninvasive measurements of blood pressure (BP) and cardiac output (CO) are crucial in the follow‐up of continuous‐flow left ventricular assist device (CF‐LVAD) patients. For our pilot study, we sought to compare BP measurements between a tonometry blood pressure pulse analyzer (BPPA) (DMP‐Life, DAEYOMEDI Co., Ltd., Gyeonggi‐do, South Korea) and Doppler ultrasound in CF‐LVAD patients, as well as to compare the BPPA estimated CO to LVAD calculated blood flow and to the patient's intrinsic CO estimated with transthoracic echocardiography (TTE). Ambulatory CF‐LVAD patients (6 HeartMate, 26 HeartMate II), were included. According to TTE findings, patients were then subdivided in two groups: patients with an opening aortic valve (OAV) [n = 21] and those with an intermittent opening aortic valve (IOAV) [n = 11]. We found a very good correlation of systolic BP (SBP) measurements between the two methods, BPPA and Doppler ultrasound (r = 0.87, P < 0.0001). Bland‐Altman plots for SBP revealed a low bias of −4.6 mm Hg and SD of ±4.7 mm Hg. In CF‐LVAD patients with IOAV, the BPPA‐CO had a good correlation with the LVAD‐flow (r = 0.78, P < 0.0001), but in OAV patients, there was no correlation. After adding the patient's intrinsic CO, estimated from TTE in patients with OAV to the LVAD‐flow, we found a very good correlation between the BPPA‐CO and LVAD‐flow + TTE‐CO (r = 0.81, P = 0.002). Our study demonstrated that compared with the standard clinical method, Doppler ultrasound, the BPPA measured BP noninvasively with good accuracy and precision of agreement. In addition, tonometry BPPA provided further valuable information regarding the CF‐LVAD patient's intrinsic CO. [ABSTRACT FROM AUTHOR]

Artificial hearts are effective devices to treat heart failure in clinical practice and can be divided into two categories: artificial hearts and ventricular assist devices. The goal of this work was to investigate the fluidity and biological changes of in vitro sheep blood using a novel alternating current (AC) magnetohydrodynamic blood pump (central magnetic intensity: 0.9 T, alternating current frequency of the electric motor: 0–80 Hz). Blood samples were collected from five sheep and were divided into two groups: the control group (no exposure to an external magnetic field) and the exposed group (3 h of exposure to an alternating magnetic field). The blood cell counts, changes in blood viscosity, and ultrastructural changes of the blood cells under transmission electron microscopy were investigated. This study demonstrated several findings: (i) Continuous sheep blood flow can be achieved; (ii) The blood cell counts remained unchanged after 3 h of exposure to an alternating magnetic field; (iii) Compared with the control group, the high‐ and low‐shear viscosities of the whole blood from the sheep significantly decreased after 3 h of exposure to an alternating magnetic field (P < 0.05 and P < 0.01, respectively). Plasma viscosity was significantly reduced after exposure to high‐intensity alternating magnetic fields (P < 0.001); (iv) The cytoplasm of blood cells (especially erythrocytes) became lighter in color in the exposure group compared to the control group, and "beads‐on‐string" aggregations of black particles appeared. This work provides detailed and reliable scientific research data for the development of this type of blood pump, which may serve as a transition to the clinical artificial heart. [ABSTRACT FROM AUTHOR]

Although rotary blood pumps (RBPs) sustain life, blood exposure to continuous supra‐physiological shear stress induces adverse effects (e.g., thromboembolism); thus, pulsatile flow in RBPs represents a potential solution. The present study introduced pulsatile flow to the HeartWare HVAD using a custom‐built controller and compared hemocompatibility biomarkers (i.e., platelet aggregation, concentrations for ADAMTS13, von Willebrand factor (vWf), and free‐hemoglobin in plasma (pfHb), red blood cell (RBC) deformability, and RBC‐nitric oxide synthase (NOS) activity) between continuous and pulsatile flow in a blood circulation loop over 5 h. The HeartWare HVAD was operated using a custom‐built controller, at continuous speed (3282 rev/min) or in a pulsatile mode (mean speed = 3273 rev/min, amplitude = 430 rev/min, frequency = 1 Hz) to generate a blood flow rate of 5.0 L/min, HVAD differential pressure of 90 mm Hg for continuous flow and 92 mm Hg for pulsatile flow, and systolic and diastolic pressures of 121/80 mm Hg. For both flow regimes, the current study found; (i) ADP‐ and collagen‐induced platelet aggregation, and ADAMTS13 concentration significantly decreased after 5 h (P < 0.01; P < 0.05), (ii) ristocetin‐induced platelet aggregation significantly increased after 45 min (P < 0.05), (iii) vWf concentration did not significantly differ at any time point, (iv) pfHb significantly increased after 5 h (P < 0.01), (v) RBC deformability improved during the continuous flow regime (P < 0.05) but not during pulsatile flow, and (vi) RBC‐NOS activity significantly increased during continuous flow (15 min), and pulsatile flow (5 h; P < 0.05). The current study demonstrated: (i) speed modulation does not improve hemocompatibility of the HeartWare HVAD based on no observable differences being detected for routine biomarkers, and (ii) the time‐course for increased RBC‐NOS activity observed during continuous flow may have improved RBC deformability. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the effects of nonpulsatile and ECG‐synchronized pulsatile extracorporeal life support on coronary and carotid blood flow velocities using transthoracic echocardiography and vascular ultrasound, respectively. Nine adult swine were randomly separated into nonpulsatile (NP, n = 5) and pulsatile (P, N = 4) groups and placed on ECLS for 24 h using an i‐cor ECLS system. Noninvasive transthoracic images of the left and right coronary artery and the left carotid artery were acquired at the pre‐ECLS (baseline), 30 min, 3, 6, 9, 12, and 24 h on‐ECLS stages. The mean diastolic velocity of the left and right coronary arteries in the NP group significantly decreased after 24 h on ECLS compared to the baseline and 30 min ECLS stages (P < 0.05). There was no statistical difference in the mean diastolic velocity of the coronary arteries in the P group at 30 min, 3‐, 6‐, 9‐, 12‐, and 24‐h ECLS compared to baseline. The P group showed a smaller decrease in the mean diastolic velocity of coronary arteries between the 30‐min ECLS and 3‐, 6‐, 9‐, 13‐, 24‐h ECLS stages compared to the NP group. The diastolic velocity of the left carotid artery in the NP group significantly decreased during 24‐h ECLS compared to the P group (P < 0.05). An ECG‐synchronized pulsatile ECLS system appeared to maintain coronary and carotid artery diastolic velocities better than conventional nonpulsatile ECLS. Further investigation of the perfusion modes during ECLS is warranted. [ABSTRACT FROM AUTHOR]

Abstract: In renal transplantation, ischemia reperfusion injury impairs early graft function and can reduce long term graft survival. Hydrogen has antioxidant and anti‐inflammatory properties that can reduce the effects of ischemic injury. The aim of this study was to examine the effects of hydrogen gas administered during reperfusion in a preclinical model of kidney ischemia reperfusion injury. Porcine kidneys underwent 15 min of warm ischemia followed by 22 h of cold ischemia. They were then reperfused for 6 h with whole autologous blood on an ex vivo reperfusion circuit. Paired kidneys were randomized to control (n = 6) (25% oxygen, 5% carbon dioxide, 70% nitrogen) or hydrogen (n = 6) (2% hydrogen, 25% oxygen, 5% carbon dioxide, 68% nitrogen) groups. Tissue, urine, and blood samples were collected at baseline and hourly throughout the reperfusion period. Baseline measurements were similar across groups. Following perfusion, there was no significant difference between control and hydrogen groups in urine output (693 mL vs. 608 mL, P = 0.86), renal blood flow (105.9 vs. 108 mL/min/100g, P = 0.89), acid‐base homeostasis, or creatinine clearance. There was a significant increase in cytokine levels from baseline to 6 h in both groups (IL‐1β P = 0.002; IL‐6 P = 0.004; IL‐8 P = 0.002). However, there were no significant differences in levels of inflammatory cytokines (IL1β, IL‐6, and IL‐8) between the groups. The administration of hydrogen gas did not improve renal function, reduce oxidative damage, or inflammation during the reperfusion of ischemically damaged kidneys. [ABSTRACT FROM AUTHOR]

Abstract: Circulatory failure following cardiac arrest (CA) requires catecholamine support and occasionally veno‐arterial extracorporeal membrane oxygenation (vaECMO). VaECMO‐generated blood flow is continuous and retrograde, increasing ventricular stroke work. Our aim was to assess the benefit of a device generating a pulsatile vaECMO flow synchronized with the heart rhythm lowering systolic vaECMO output on the left ventricular ejection fraction (LVEF) and pulmonary capillary pressure (Pcap) after CA. This experimental randomized study in pigs compared standard nonpulsatile vaECMO (control) with pulsatile synchronized vaECMO (study) group using a pulsatility‐generating device. After sedation and intubation, ventricular fibrillation was induced by pacing. After 10‐min ventricular fibrillation, cardiopulmonary resuscitation was performed for 20 min then vaECMO, defibrillation and 0.15 µg/kg/min intravenous epinephrine infusion were initiated. Hemodynamics, Pcap, LVEF by echocardiography and angiography were measured at baseline and every 30 min after the vaECMO start until vaECMO and epinephrine were stopped (at 120 min), and 30 min later. Baseline hemodynamics did not differ between groups; 120 min after vaECMO initiation, LVEF by echocardiography and angiography was significantly higher in the study than control group 55 ± 19% versus 34 ± 13% (P = 0.042), 50 ± 16% versus 33 ± 12% (P = 0.043), respectively. Pcap decreased from baseline by 4.2 ± 8.6 mm Hg in the study group but increased by 5.6 ± 5.9 mm Hg in the control group (P = 0.043). Thirty minutes later, LVEF remained higher in the study group 44 ± 7% versus 26 ± 11% (P = 0.008) while Pcap did not differ. A synchronized pulsatile device decreasing systolic output from vaECMO improved LVEF and Pcap in a pig model of CA and resuscitation. [ABSTRACT FROM AUTHOR]

Abstract: To assess the hemodynamic effects of connection to continuous renal replacement therapy (CRRT) in a pediatric experimental animal model. Prospective experimental study was performed using piglets between 2 and 3 months of age and 9–11 kg. CRRT with a PrismaflexR monitor and HF20 filter (surface of 0.2 m2) was started after monitoring and anesthetic induction with an initial blood flow at 20 mL/min with 10 mL/min increases every minute until the goal flow of 5 mL/kg/min was achieved. Heart rate, blood pressure, central venous pressure, cardiac index, and renal blood flow were registered at baseline, 5, 15, 30, 60, 120, 180, 240, and 360 min. IBM SPSS Statistics 20.0 package was used for analysis. A P value of <0.05 was considered statistically significant. Thirty‐four piglets were studied. Blood pressure, cardiac output, and systemic vascular resistance significantly decreased 5‐min after CRRT connection (mean arterial pressure from 85.5 to 70.8 mm Hg, P < 0.001, cardiac index from 3.6 to 3.3 L/min/m2 P = 0.024, and systemic vascular resistance index from 1759 to 1607 dyn.s/cm5 P = 0.012). No significant changes were found in renal blood flow or central venous pressure. All parameters gradually increased at 15 and 30 min after connection but complete recovery was never achieved. Connection to CRRT produces a significant decrease in arterial pressure, cardiac index, and peripheral vascular resistances in hemodynamically stable piglets. [ABSTRACT FROM AUTHOR]

Abstract: Design of contemporary oxygenators requires better understanding of the influence of hydrodynamic patterns on gas exchange. A decrease in blood path width or an increase in intraoxygenator turbulence for instance, might increase gas transfer efficiency but it will increase shear stress as well. The aim of this clinical study was to examine the association between shear stress and oxygen and carbon dioxide transfer in different contemporary oxygenators during cardiopulmonary bypass (CPB). The effect of additional parameters related to gas transfer efficiency, that is, blood flow, gas flow, sweep gas oxygen fraction (FiO2), hemoglobin concentration, the amount of hemoglobin pumped through the oxygenator per minute—Qhb, and shunt fraction were contemplated as well. Data from 50 adult patients who underwent elective CPB for coronary artery bypass grafting or aortic valve replacement were retrospectively analyzed. Data included five different oxygenator types with an integrated arterial filter. Relationships were determined using Pearson bivariate correlation analysis and scatterplots with LOESS curves. In the Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i groups, mean blood flows were 4.8 ± 0.9, 5.3 ± 0.7, 4.9 ± 0.7, 5.0 ± 0.6, and 5.7 ± 0.6 L/min, respectively. The mean O2 transfer/m2 membrane surface area was 44 ± 14, 51 ± 9, 60 ± 10, 63 ± 14, and 77 ± 18, respectively, whereas the mean CO2 transfer/m2 was 26 ± 14, 60 ± 22, 73 ± 29, 74 ± 19, and 96 ± 20, respectively. Associations between oxygen transfer/m2 and shear stress differed per oxygenator, depending on oxygenator design and the level of shear stress (r = 0.249, r = 0.562, r = 0.402, r = 0.465, and r = 0.275 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). Similar associations were noted between CO2 transfer/m2 and shear stress (r = 0.303, r = 0.439, r = 0.540, r = 0.392, and r = 0.538 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). In addition, O2 transfer/m2 was strongly correlated with FiO2 (r = 0.633, P < 0.001), blood flow (r = 0.529, P < 0.001), and Qhb (r = 0.589, P < 0.001). CO2 transfer/m2 in contrast was predominately correlated to sweep gas flow (r = 0.567, P < 0.001). The design‐dependent relationship between shear stress and gas transfer revealed that every oxygenator has an optimal range of blood flow and thus shear stress at which gas transfer is most efficient. Gas transfer is further affected by factors influencing the O2 or CO2 concentration gradient between the blood and the gas compartment. [ABSTRACT FROM AUTHOR]