Predictors of membrane oxygenator failure in pediatric extracorporeal membrane oxygenation.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is increasingly utilized in pediatric patients. Failure to recognize membrane oxygenator failure can lead to critical complications due to rapid deterioration of membrane oxygenator function. Therefore, identifying the predictors for membrane oxygenator exchange is crucial. However, risk factors for membrane oxygenator exchange in pediatric V-A ECMO remain unclear; therefore, this study aimed to evaluate these risk factors. METHODS: This retrospective cohort study enrolled all pediatric patients aged <18 years who received V-A ECMO between August 2018 and July 2023 at a tertiary-care pediatric hospital in Japan. The Cox proportional hazards model was used to evaluate the predictors of membrane oxygenator failure within 72 h after initiation. RESULTS: During the study period, membrane oxygenator failure occurred in 18/55 (32.7%) children within 72 h; membrane oxygenator failure within 72 h occurred in 4/29 (13.8%) and 14/26 (53.8%) in the groups with ratio of blood flow divided by the blood flow limit of the membrane oxygenator (B/L) of <0.5 and ≥0.5, respectively (adjusted hazards ratio, 4.97 [95% confidence interval, 1.33-18.5]; p = 0.017). After adjusting for delta pressure of the oxygenator, an increase in body weight and aspartate aminotransferase levels were associated with an increase in early membrane oxygenator failure. CONCLUSIONS: This retrospective study demonstrated that a B/L ratio >0.5, an increase in body weight, and elevated aspartate aminotransferase were independent risk factors for early membrane oxygenator failure in pediatric V-A ECMO. However, a prospective multicenter study with an appropriate sample size is warranted to mitigate potential bias, and enhance generalizability for further investigation of the association between a B/L ratio and early membrane oxygenator failure.

3D porous structure imaging of membranes for medical devices using scanning probe microscopy and electron microscopy: from membrane science points of view.

The evolution of hemodialysis membranes (dialyzer, artificial kidney) was remarkable, since Dow Chemical began manufacturing hollow fiber hemodialyzers in 1968, especially because it involved industrial chemistry, including polymer synthesis and membrane manufacturing process. The development of hemodialysis membranes has brought about the field of medical devices as a major industry. In addition to conventional electron microscopy, scanning probe microscopy (SPM), represented by atomic force microscopy (AFM), has been used in membrane science research on porous membranes for hemodialysis, and membrane science contributes greatly to the hemodialyzer industry. Practical studies of membrane porous structure-function relationship have evolved, and methods for analyzing membrane cross-sectional morphology were developed, such as the ion milling method, which was capable of cutting membrane cross sections on the order of molecular size to obtain smooth surface structures. Recently, following the global pandemic of SARS-CoV-2 infection, many studies on new membranes for extracorporeal membrane oxygenator have been promptly reported, which also utilize membrane science researches. Membrane science is playing a prominent role in membrane-based technologies such as separation and fabrication, for hemodialysis, membrane oxygenator, lithium ion battery separators, lithium recycling, and seawater desalination. These practical studies contribute to the global medical devices industry.

Hypobaric type oxygenators - physics and physiology.

Brain injury is still a serious complication after cardiac surgery. Gaseous microemboli (GME) are known to contribute to both short and longer-term brain injury after cardiac surgery. Hypobaric and novel dual-chamber oxygenators use the physical behaviors and properties of gases to reduce GME. The aim of this review was to present the basic physics of the gases, the mechanism in which the hypobaric and dual-chamber oxygenators reduce GME, their technical performance, the preclinical studies, and future directions. The gas laws are reviewed as an aid to understanding the mechanisms of action of oxygenators. Hypobaric-type oxygenators employ a high oxygen, no nitrogen environment creating a steep concentration gradient of nitrogen out of the blood and into the oxygenator, reducing the risk of GMEs forming. Adequately powered clinical studies have never been carried out with a hypobaric or dual-chamber oxygenator. These are required before such technology can be recommended for widespread clinical use.

The effect of excessive gas to blood ratios in an ECMO oxygenator.

INTRODUCTION: Oxygenators for paediatric Extracorporeal Membrane Oxygenation (ECMO) are required to operate over a wide range of flow rates, in a patient group ranging from neonates through to fully grown adolescents. ECMO oxygenators typically have a manufacturer's stated maximum gas: blood flow rate (GBFR) ratio of 2:1, however, many patients require greater ratios than this for adequate CO2 removal. Mismatches in GBFR in theory could result in high gas phase pressures. These increased pressures in theory could cause the formation of gross gaseous microemboli (GME) placing the child at higher risk of neurological injury. METHODS: We evaluated 6 paediatric and 6 adult A.L.ONE™ ECMO oxygenators and assessed their gas phase pressures and GME release, in an ex vivo setting, in GBFR ratios up to greater than 2, across a range of gas flow (1L - 10 L/min) rates with a fraction of inspired oxygen (FiO2) content of 50% and 100%. RESULTS: There were no increases above 10 mmHg observed in gas phase pressures in GBFR >= 2:1 in either adult or paediatric oxygenators. Laboratory examination of GME activity demonstrated a small increase in post-membrane GME release over the study period. GME release was unaffected by FiO2 setting or gas flow rate, with a maximum volume of < 6 µL in both paediatric and adult oxygenators. CONCLUSIONS: In an ex vivo setting, increasing GBFR above 2:1 in a paediatric oxygenator, and to a GBFR of 2:1 in an adult oxygenator did not significantly increase gas phase pressures, and no oxygenator membrane rupture was observed. There were no associations between gas flow rates and GME production.

Sudden pump stop may cause air release in oxygenators, 'The Hammer Effect ': An in vitro evaluation.

BACKGROUND: Oxygenators, as used in cardiopulmonary bypass (CPB) circuits, are components with good air removal properties. However, under some conditions the semipermeable characteristics of hollow fibers allow air to accidentally enter the blood side of the CPB circuit. This may occur when a fluid in motion is stopped suddenly by which the rapid change in momentum may cause a relative negative pressure drop, the so-called hammer effect. The hammer effect is not yet described in literature related to CPB. The aim of this in vitro study was to reproduce the hammer effect. METHODS: The in vitro setup consisted of a CPB circuit with a fully occluded roller pump and one of four test oxygenators. The hammer test was performed by a sudden pump stop. The pressure wave was measured and after the test the residual air present in the oxygenator was forced into the arterial line and measured with a bubble detector. RESULTS: We showed that a sudden pump stop could lead to the hammer effect, represented as a relative negative pressure drop in the arterial line. This hammer effect resulted in air release through the semipermeable fibers as we showed in two of the four tested brands of oxygenators. CONCLUSIONS: We conclude that the hammer effect may occur before connection of the CPB system to the patient, and this may result in air release into the arterial blood side of the oxygenator. The hammer effect can be caused by clamping of the tubing in combination with a centrifugal pump, or by suddenly stopping the roller pump. With this study we would like to raise awareness of the hammer effect.

Feasibility, safety, and efficacy of Atrial Flow Regulator in children under 10 kg.

INTRODUCTION: The Atrial Flow Regulator (AFR) is a new self-expandable percutaneous-delivered fenestrated device providing an interatrial shunt. Its use in pediatric population has been reported in failing Fontan, pulmonary hypertension, or in patients with cardiomyopathy and venoarterial extracorporeal membrane oxygenator (ECMO) support. Its use in small children under 10 kg has not been reported. METHODS: We report the initial single center experience of the AFR implantation in children below 10 kg. RESULTS: Four children underwent AFR implantation. Patients' age and weight ranged between 9 and 22 months and 5-8.7 kgs. Indications were to unload the left atrium during ECMO support for end-stage cardiomyopathy and to enlarge a restrictive interatrial shunt in two other patients with complex congenital heart diseases. Devices implanted were AFR-6 and AFR-8. Delivery sheaths used via venous femoral access were undersized and ranged from 9 to 11 Fr. Devices were successfully implanted and provided unrestrictive interatrial shunt in all cases. One child developed a nonocclusive thrombus in the inferior vena cava which resolved within 1 month. Clinical improvement and femoral vein patency were observed in all cases. CONCLUSION: AFR implantation is feasible in selected children under 10 kg. The AFR can be safely deployed through sheaths that are 1-2 Fr smaller than the recommended manufacturer size. More studies are needed to confirm safety and efficacy of the device in selected pediatric patients.

Circuit change during extracorporeal membrane oxygenation: single-center retrospective study of 48 changes.

BACKGROUND: Bleeding and thrombosis induce major morbidity and mortality in patients under extracorporeal membrane oxygenator (ECMO). Circuit changes can be performed for oxygenation membrane thrombosis but are not recommended for bleeding under ECMO. The objective of this study was to evaluate the course of clinical, laboratory, and transfusion parameters before and after ECMO circuit changes warranted by bleeding or thrombosis. METHODS: In this single-center, retrospective, cohort study, clinical parameters (bleeding syndrome, hemostatic procedures, oxygenation parameters, transfusion) and laboratory parameters (platelet count, hemoglobin, fibrinogen, PaO2) were collected over the seven days surrounding the circuit change. RESULTS: In the 274 patients on ECMO from January 2017 to August 2020, 48 circuit changes were performed in 44 patients, including 32 for bleeding and 16 for thrombosis. Mortality was similar in the patients with vs. without changes (21/44, 48% vs. 100/230, 43%) and in those with bleeding vs. thrombosis (12/28, 43% vs. 9/16, 56%, P = 0.39). In patients with bleeding, numbers of bleeding events, hemostatic procedures, and red blood cell transfusions were significantly higher before vs. after the change (P < 0.001); the platelet counts and fibrinogen levels decreased progressively before and increased significantly after the change. In patients with thrombosis, numbers of bleeding events and red blood cell transfusions did not change after membrane change. No significant differences were demonstrated between oxygenation parameters (ventilator FiO2, ECMO FiO2, and PaO2) and ECMO flow before vs. after the change. CONCLUSIONS: In patients with severe and persistent bleeding, changing the ECMO circuit decreased clinical bleeding and red blood cell transfusion needs and increased platelets and fibrinogen levels. Oxygenation parameters did not change significantly in the group with thrombosis.

Development and evaluation of a variable, miniaturized oxygenator for various test methods.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) became an accepted therapy for the treatment of severe acute respiratory distress syndrome and chronic obstructive pulmonary disease. However, ECMO systems are still prone to thrombus formation and decrease of gas exchange over time. Therefore, it is necessary to conduct qualified studies to identify parameters for optimization of ECMO systems, and especially the oxygenator. However, commercially marketed oxygenators are not always appropriate and available for certain research use cases. Therefore, we aimed to design an oxygenator, which is suitable for various test conditions such as blood tests, numerical simulation, and membrane studies, and can be modified in membrane area size and manufactured in laboratory. METHODS: Main design criteria are a homogeneous blood flow without stagnation zones, low pressure drop, manufacturability in the lab, size variability with one set of housing parts and cost-efficiency. Our newly designed oxygenator was tested comparatively regarding blood cell damage, gas transfer performance and pressure drop to prove the validity of the design in accordance with a commercial device. RESULTS: No statistically significant difference between the tested oxygenators was detected and our new oxygenator demonstrated sufficient hemocompatibility. Furthermore, our variable oxygenator has proven that it can be easily manufactured in the laboratory, allows to use various membrane fiber configurations and can be reopened easily and non-destructively for analysis after use, and the original geometry is available for numerical simulations. CONCLUSION: Therefore, we consider this newly developed device as a valuable tool for basic experimental and numerical research on the optimization of oxygenators.

Improving adult pulsatile minimal invasive extracorporeal circulation in a mock circulation.

BACKGROUND: Pulsatile extracorporeal circulation (ECC) may improve perfusion of critical organs during cardiac surgery. This study analyzed the influence of the components of a minimal invasive ECC (MiECC) on the transfer of pulsatile energy into the pseudo-patient of a mock circulation. METHODS: An aortic model with human-like geometry and compliance was perfused by a diagonal pump. Surplus hemodynamic energy (SHE) was determined from flow and pressure data. Five adult-size oxygenator models and three sizes of cannulas were compared. Pulsatile pump settings were optimized, and parallel dual-pump configurations were evaluated. RESULTS: Oxygenator models showed up to twofold differences in pressure gradients and influenced SHE at flow rates up to 2.0 L min-1 . Adjustments of frequency, systole duration, and rotational speed gain significantly improved SHE compared with empirical settings, with SHE above 21% of mean arterial pressure at flow rates of 1.0 L min-1 to 1.5 L min-1 and SHE above 5% at 3.5 L min-1 . Small diameter cannula (15 Fr) limited SHE compared with larger cannula (21 Fr and 23 Fr). Two diagonal pumps did not provide higher SHE than a single pump, but permitted additional control over pulse pressure and SHE by varying the total fraction of pulsatile flow and the fraction of flow bypassing the oxygenator. CONCLUSIONS: Proper selection of components and optimizations of pump settings significantly improved pulse pressure and SHE of pulsatile MiECC. Surplus hemodynamic energy depended on flow rate with a maximum at 1.0 L min-1 -1.5 L min-1 . Pulsatile MiECC may specifically assist organ perfusion during phases of low flow.

Innovative experimental animal models for real-time comparison of antithrombogenicity between two oxygenators using dual extracorporeal circulation circuits and indocyanine green fluorescence imaging.

BACKGROUND: Antithrombogenicity of extracorporeal membrane oxygenation (ECMO) devices, particularly oxygenators, is a current problem, with numerous studies and developments underway. However, there has been limited progress in developing methods to accurately compare the antithrombogenicity of oxygenators. Animal experiments are commonly conducted to evaluate the antithrombogenicity of devices; however, it is challenging to maintain a steady experimental environment. We propose an innovative experimental animal model to evaluate different devices in a constant experimental environment in real-time. METHODS: This model uses two venous-arterial ECMO circuits attached to one animal (one by jugular vein and carotid artery, one by femoral vein and artery) and real-time assessment of thrombus formation in the oxygenator by indocyanine green (ICG) fluorescence imaging. Comparison studies were conducted using three pigs: one to compare different oxygenators (MERA vs. CAPIOX) (Case 1), and two to compare antithrombotic properties of the oxygenator (QUADROX) when used under different hydrodynamic conditions (continuous flow vs. pulsatile flow) (Cases 2 and 3). RESULTS: Thrombi, visualized using ICG imaging, appeared as black dots on a white background in each oxygenator. In Case 1, differences in the site of thrombus formation and rate of thrombus growth were observed in real-time in two oxygenators. In Case 2 and 3, the thrombus region was smaller in pulsatile than in continuous conditions. CONCLUSIONS: We devised an innovative experimental animal model for comparison of antithrombogenicity in ECMO circuits. This model enabled simultaneous evaluation of two different ECMO circuits under the same biological conditions and reduced the number of sacrificed experimental animals.

Risk factors for elective and emergency oxygenator exchanges during veno-venous extracorporeal membrane oxygenation.

BACKGROUND: Despite systemic anticoagulation and antithrombotic surface coating, oxygenator dysfunction remains one of most common technical complications of Extracorporeal membrane oxygenation (ECMO). Several parameters have been associated with an oxygenator exchange, but no guidelines for when to perform an exchange are published. An exchange, especially an emergency exchange, has a risk of complications. Therefore, a delicate balance between oxygenator dysfunction and the exchange of the oxygenator exists. This study aimed to identify risk factors and predictors for elective and emergency oxygenator exchanges. METHODS: This observational cohort study included all adult patients supported with veno-venous extracorporeal membrane oxygenation (V-V ECMO). We compared patients' characteristics and laboratory values of patients with and without an oxygenator exchange and between an elective and emergency exchange, defined as an exchange outside office hours. Risk factors for an oxygenator exchange were identified with cox regression analyses, and risk factors for an emergency exchange were identified with logistic regression analyses. RESULTS: We included forty-five patients in the analyses. There were twenty-nine oxygenator exchanges in nineteen patients (42%). More than a third of the exchanges were emergency exchanges. Higher partial pressure of carbon dioxide (PaCO2), transmembrane pressure difference (ΔP), and hemoglobin (Hb) were associated with an oxygenator exchange. Lower lactate dehydrogenase (LDH) was the only risk factor for an emergency exchange. CONCLUSION: Oxygenator exchange is frequent during V-V ECMO support. PaCO2, ΔP and Hb were associated with an oxygenator exchange and lower LDH with the risk of an emergency exchange.

Risk factors and treatment of oxygenator high-pressure excursions during cardiopulmonary bypass.

INTRODUCTION: A high-pressure excursion (HPE) is a sudden increase in oxygenator inlet pressure during cardiopulmonary bypass (CPB). The aims of this study were to identify factors associated with HPE, to describe a treatment protocol utilizing epoprostenol in severe cases, and to assess early outcome in HPE patients. METHODS: Patients who underwent cardiac surgery with cardiopulmonary bypass at Sahlgrenska University Hospital 2016-2018 were included in a retrospective observational study. Pre- and post-operative data collected from electronic health records, local databases, and registries were compared between HPE and non-HPE patients. Factors associated with HPE were identified with logistic regression models. RESULTS: In total, 2024 patients were analyzed, and 37 (1.8%) developed HPE. Large body surface area (adjusted Odds Ratio (aOR): 1.43 per 0.1 m2; 95% confidence interval (CI): 1.16-1.76, p < 0.001), higher hematocrit during CPB (aOR: 1.20 per 1%; (1.09-1.33), p < 0.001), acute surgery (aOR: 2.98; (1.26-6.62), p = 0.018), and previous stroke (aOR: 2.93; (1.03-7.20), p = 0.027) were independently associated with HPE. HPE was treated with hemodilution (n = 29, 78.4%), and/or extra heparin (n = 23, 62.2%), and/or epoprostenol (n = 12, 32.4%). No oxygenator change-out was necessary. While there was no significant difference in 30-day mortality (2.7% vs 3.2%, p = 1.0), HPE was associated with a higher perioperative stroke rate (8.1% vs 1.8%, aOR 5.09 (1.17-15.57), p = 0.011). CONCLUSIONS: Large body surface area, high hematocrit during CPB, previous stroke and acute surgery were independently associated with HPE. A treatment protocol including epoprostenol appears to be a safe option. Perioperative stroke rate was increased in HPE patients.

Clinical evaluation of the novel Capiox NX19 adult oxygenator-a multicenter study.

INTRODUCTION: The novel Capiox NX19 adult oxygenator is, compared to its predecessors, improved with enhanced air removal technology, a polymer heat exchanger and smaller, innovative hollow fibers resulting in a surface area reduction and a lower priming volume. The aim of this study was to evaluate the NX19 oxygenator performance in a clinical setting. METHODS: A prospective multicenter study was performed involving three large European university hospitals. The Capiox NX19 (n = 150) performance was assessed during adult cardiopulmonary bypass and involved gaseous microemboli handling and gas transfer efficiency. The heat exchanger performance was evaluated separately in vitro. RESULTS: The heat exchanger performance factors were 0.80 ± 0.03 and 0.58 ± 0.04 at pump flow rates of 3 L/min and 6 L/min, respectively. After priming, residual post-oxygenator gaseous microemboli count and volume were decreased by 91% and 93.7%, respectively. The gas compartment pressure was 6.0 ± 2.5 mmHg, while the O2 transfer was 69 ± 30 mL/min/m2 and the CO2 transfer 73 ± 34 mL/min/m2. The O2 gradient was 44 ± 19 mmHg/LPM and the O2 diffusing capacity 0.38 ± 0.14 mL/min/mmHg. The shunt fraction was 0.19 ± 0.13, whereas oxygenator resistance and shear stress were 10.5 ± 3.7 mmHg/LPM and 5.1 ± 3.1 dyn/cm2, respectively. CONCLUSION: This multicenter study displayed good clinical safety and performance of the NX19 oxygenator.

Oxygenator impact on peramivir in extra-corporeal membrane oxygenation circuits.

INTRODUCTION: This study aims to determine the oxygenator impact on alterations of peramivir (PRV) in a contemporary neonatal/pediatric (1/4-inch) and adolescent/adult (3/8-inch) extra-corporeal membrane oxygenation (ECMO) circuit including the Quadrox-i® oxygenator. METHODS: 1/4-inch and 3/8-inch, simulated closed-loop ECMO circuits were prepared with a Quadrox-i pediatric and Quadrox-i adult oxygenator and blood primed. Additionally, 1/4-inch and 3/8-inch circuits were also prepared without an oxygenator in series. A one-time dose of PRV was administered into the circuits and serial pre- and post-oxygenator concentrations were obtained at 5-min and 1-, 2-, 3-, 4-, 5-, 6-, 8-, 12-, and 24-h time points. PRV was also maintained in a glass vial, and samples were taken from the vial at the same time periods for control purposes to assess for spontaneous drug degradation. RESULTS: For the 1/4-in. circuit with an oxygenator, there was < 15% PRV loss, and for the 1/4-in. circuit without an oxygenator, there was < 3% PRV loss during the study period. For the 3/8-in. circuits with an oxygenator, there was < 15% PRV loss, and for the 3/8-in. circuits without an oxygenator, there was < 3% PRV loss during the study period. CONCLUSION: There was no significant PRV loss over the 24-h study period in either the 1/4-in. or 3/8-in circuit, regardless of the presence of the oxygenator. The concentrations obtained pre- and post-oxygenator appeared to approximate each other, suggesting there may be no drug loss via the oxygenator. This preliminary data suggests PRV dosing may not need to be adjusted for concern of drug loss via the oxygenator. Additional single and multiple dose studies are needed to validate these findings.

Comparison of bubble removal performances of five membrane oxygenators with and without a pre-filter.

When employing minimal invasive extracorporeal circulation (MiECC), the removal of bubbles in the circuit is important to prevent air embolism. We investigated the bubble removal performance of the FHP oxygenator with a pre-filter and compared it with that of four oxygenators, including the Fusion oxygenator, Quadrox oxygenator, Inspire oxygenator, and FX oxygenator. A closed test circuit filled with an aqueous glycerin solution was used. Air injection (10 mL) was performed prior to the oxygenator, and the number and volume of the bubbles were measured at the inlet and outlet of each oxygenator. At the inlet of the five oxygenators, there were no significant differences in the total number of bubbles detected. At the outlet, bubbles were classified into two groups according to the bubble size: ≥100 µm and <100 µm. Tests were performed at pump flow rates of 4 and 5 L/min. For bubbles ≥100 µm, which are considered clinically detrimental, the FHP was the lowest number and volume of bubbles at both pump flow rates compared to the other oxygenators. Regarding the bubbles <100 µm, the number of bubbles was higher in the FHP than those in others; however, the volume of bubbles was significantly lower at 4 L/min and tended to be lower at 5 L/min. The use of the FHP with the pre-filter removed more bubbles ≥100 µm in the circuit than that by the other oxygenators.

Use of cardiopulmonary bypass machine in intensive care unit as a short term mechanical circulatory support for recovery of cardiac function.

INTRODUCTION: Extracorporeal Membrane Oxygenation (ECMO) is used as a bridge to recovery of cardiac function following completion of congenital cardiac surgeries where there is failure to wean from cardiopulmonary bypass (CPB) or severe low cardiac output states in the post operative periods. Although ECMO is a well-established form of mechanical circulatory support, the associated cost can be a huge financial burden on families. We are an ECMO center and use the same in post operative congenital cardiac surgeries for mechanical cardiovascular support if needed. However, a significant proportion of the children, whom we operate, are funded by government aides. The resources are limited in such circumstances. If needed, we use the same CPB circuit and cannulae used in the Operating Room (OR) and support them at a significantly lower cost compared to ECMO. METHODS: We report our experience of using conventional CPB machine as a short-term bridge to recovery of cardiac function in Intensive Care Unit where there was limitation of funds. Essentially same CPB circuit with roller pump is retained, by omitting cardiotomy suckers. We use D901 Lilliput 1 Oxygenator (Sorin, Italy) for children <5 kg and D902 Lilliput 2 (Sorin, Italy) Oxygenator for children >5 Kg. RESULTS: We supported nine patients on CPB between March 2019 and December 2021. During this time, 1392 congenital cardiac surgeries were performed. We could wean off three patients (33.3%) and discharge two patients (22.2%). Our support time ranged from 21 h to 60 h with a median of 48 h. Beyond 48 h of support, we experienced several CPB induced complications in our cohort. CONCLUSION: In resource-limited settings, conventional CPB machines can be used for short-term cardiac support. Although results may not be comparable to using ECMO, some patients can be definitely salvaged, who would otherwise die in the absence of institution of mechanical circulatory support.

In vitro evaluation of the performance of an oxygenator depending on the non-standard gas content of the inlet blood with special regard on CO2 elimination.

INTRODUCTION: The performance of an oxygenator, as found in literature, is evaluated according to protocols that define standard values of the gas content in the inlet blood. However, when dealing with simulations of lung insufficiency, a more extensive evaluation is needed. This work aims to investigate and assess the gas exchange performance of an oxygenator for different input values of gas content in blood. METHODS: Three commercially available oxygenators with different membrane surfaces were investigated in a mock loop for three blood flow rates (0.5l/min, 1l/min, and 5l/min) and two gas-to-blood ratios (1:1, and 15:1). The initial CO2 and O2 partial pressures (pCO2 and pO2) in blood were set to ≥ 100 mmHg and ≤10 mmHg, respectively. For each ratio, the efficiency, defined as the ratio between the difference of pressure inlet and outlet and the inlet pCO2 (pCO2(i)), was calculated. RESULTS: The CO2 elimination in an oxygenator was higher for higher pCO2(i). While for a pCO2(i) of 100 mmHg, an oxygenator eliminated 80 mmHg, the same oxygenator at the same conditions eliminated 5 mmHg CO2 when pCO2(i) was 10 mmHg. The efficiency of the oxygenator decreased from 76,9% to 49,5%. For simulation reasons, the relation between the pCO2(i) and outlet (pCO2(o)) for each oxygenator at different blood and gas flows, was described as an exponential formula. CONCLUSION: The performance of an oxygenator in terms of CO2 elimination depends not only on the blood and gas flow, but also on the initial pCO2 value. This dependence is crucial for simulation studies in the future.

Hemodynamic oxygenator exchange-related effects during veno-venous extracorporeal membrane oxygenation for the treatment of acute SARS-CoV-2 respiratory distress syndrome.

Few patients with coronavirus disease 2019-associated severe acute respiratory distress syndrome (ARDS) require veno-venous extracorporeal membrane oxygenation (VV-ECMO). Prolonged VV-ECMO support necessitates repeated oxygenator replacement, increasing the risk for complications. Transient hypoxemia, induced by VV-ECMO stop needed for this procedure, may induce transient myocardial ischemia and acutely declining cardiac output in critically ill patients without residual pulmonary function. This is amplified by additional activation of the sympathetic nervous system (tachycardia, pulmonary vasoconstriction, and increased systemic vascular resistance). Immediate reinjection of the priming solution of the new circuit and induced acute iatrogenic anemia are other potentially reinforcing factors. The case of a critically ill patient presented here provides an instructive illustration of the hemodynamic relationships occurring during VV-ECMO support membrane oxygenator exchange.

Comparison of complement consumption and platelet accumulation between membrane oxygenators coated with a polymer or heparin.

INTRODUCTION: The membrane oxygenator in extracorporeal circulation circuits is coated with acrylate-copolymer (ACP) or immobilized heparin (IHP) to enhance hemocompatibility. To evaluate the relative features of both coatings, we compared blood components circulated in the circuits with ACP-and IHP-coated membranes in vitro using whole human blood. METHODS: Whole human blood was heparinized and circulated in two experimental circuits with an ACP-coated reservoir, tubes, and an ACP- or IHP-coated membrane. Platelet (PLT) counts and the amount of total protein (TP), complement component 3 (C3), and complement component 4 (C4) were measured at 0, 8, 16, 24, and 32 h in each experiment (n = 5). RESULTS: The PLT count at 0-h circulation was lower in the IHP-coated than in the ACP-coated circuits (p = 0.034); however, no significant difference was observed at other time points. Reduction in TP at 8-h and 16-h circulation and in C3 at 32-h circulation was lesser in the ACP-coated than in the IHP-coated circuits (p = 0.004, 0.034, and 0.027, respectively); reduction in TP and C3 at other time points and C4 at each time point was not significantly different. There were significant interactions between coating type and circulation duration in the PLT, TP, and C3 transitions (p = 0.008, 0.020, and 0.043, respectively). CONCLUSIONS: Our findings suggest that ACP-coated membranes can prevent the initial drop in PLT count and C3 consumption over 32 h, whereas IHP-coated membranes could not prevent this drop in extracorporeal circulation. Therefore, ACP-coated membranes are suitable for short- and long-term extracorporeal life support.

Silicon membranes for extracorporeal life support: a comparison of design and fabrication methodologies.

Extracorporeal life support is an advanced therapy that circulates blood through an extracorporeal oxygenator, performing gas exchange outside the body. However, its use is limited by severe complications, including bleeding, clotting, and hemolysis. Semiconductor silicon-based membranes have emerged as an alternative to traditional hollow-fiber semipermeable membranes. These membranes offer excellent gas exchange efficiency and the potential to increase hemocompatibility by improving flow dynamics. In this work, we evaluate two next-generation silicon membrane designs, which are intended to be mechanically robust and efficient in gas exchange, while simultaneously reducing fabrication complexity. The "window" design features 10 µm pores on one side and large windows on the back side. The "cavern" design also uses 10 µm pores but contains a network of interconnected buried caverns to distribute the sweep gas from smaller inlet holes. Both designs were shown to be technically viable and able to be reproducibly fabricated. In addition, they both were mechanically robust and withstood 30 psi of transmembrane pressure without breakage or bubbling. At low sweep gas pressures, gas transfer efficiency was similar, with the partial pressure of oxygen in water increasing by 10.7 ± 2.3 mmHg (mean ± standard deviation) and 13.6 ± 1.9 mmHg for the window and cavern membranes, respectively. Gas transfer efficiency was also similar at higher pressures. At 10 psi, oxygen tension increased by 16.8 ± 5.7 mmHg (window) and 18.9 ± 1.3 mmHg (cavern). We conclude that silicon membranes featuring a 10 µm pore size can simplify the fabrication process and improve mechanical robustness while maintaining excellent efficiency.